// Copyright (c) 2015-2018 Khronos Group. This work is licensed under a // Creative Commons Attribution 4.0 International License; see // http://creativecommons.org/licenses/by/4.0/ [[primsrast]] = Rasterization Rasterization is the process by which a primitive is converted to a two-dimensional image. Each point of this image contains associated data such as depth, color, or other attributes. Rasterizing a primitive begins by determining which squares of an integer grid in framebuffer coordinates are occupied by the primitive, and assigning one or more depth values to each such square. This process is described below for points, lines, and polygons. A grid square, including its [eq]#(x,y)# framebuffer coordinates, [eq]#z# (depth), and associated data added by fragment shaders, is called a fragment. A fragment is located by its upper left corner, which lies on integer grid coordinates. Rasterization operations also refer to a fragment's sample locations, which are offset by fractional values from its upper left corner. The rasterization rules for points, lines, and triangles involve testing whether each sample location is inside the primitive. Fragments need not actually be square, and rasterization rules are not affected by the aspect ratio of fragments. Display of non-square grids, however, will cause rasterized points and line segments to appear fatter in one direction than the other. We assume that fragments are square, since it simplifies antialiasing and texturing. After rasterization, fragments are processed by the <>, if enabled. Several factors affect rasterization, including the members of sname:VkPipelineRasterizationStateCreateInfo and sname:VkPipelineMultisampleStateCreateInfo. [open,refpage='VkPipelineRasterizationStateCreateInfo',desc='Structure specifying parameters of a newly created pipeline rasterization state',type='structs'] -- The sname:VkPipelineRasterizationStateCreateInfo structure is defined as: include::../api/structs/VkPipelineRasterizationStateCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:depthClampEnable controls whether to clamp the fragment's depth values instead of clipping primitives to the z planes of the frustum, as described in <>. * pname:rasterizerDiscardEnable controls whether primitives are discarded immediately before the rasterization stage. * pname:polygonMode is the triangle rendering mode. See elink:VkPolygonMode. * pname:cullMode is the triangle facing direction used for primitive culling. See elink:VkCullModeFlagBits. * pname:frontFace is a elink:VkFrontFace value specifying the front-facing triangle orientation to be used for culling. * pname:depthBiasEnable controls whether to bias fragment depth values. * pname:depthBiasConstantFactor is a scalar factor controlling the constant depth value added to each fragment. * pname:depthBiasClamp is the maximum (or minimum) depth bias of a fragment. * pname:depthBiasSlopeFactor is a scalar factor applied to a fragment's slope in depth bias calculations. * pname:lineWidth is the width of rasterized line segments. ifdef::VK_AMD_rasterization_order[] The application can: also add a sname:VkPipelineRasterizationStateRasterizationOrderAMD structure to the pname:pNext chain of a sname:VkPipelineRasterizationStateCreateInfo structure. This structure enables selecting the rasterization order to use when rendering with the corresponding graphics pipeline as described in <>. endif::VK_AMD_rasterization_order[] .Valid Usage **** * [[VUID-VkPipelineRasterizationStateCreateInfo-depthClampEnable-00782]] If the <> feature is not enabled, pname:depthClampEnable must: be ename:VK_FALSE ifndef::VK_NV_fill_rectangle[] * [[VUID-VkPipelineRasterizationStateCreateInfo-polygonMode-01413]] If the <> feature is not enabled, pname:polygonMode must: be ename:VK_POLYGON_MODE_FILL endif::VK_NV_fill_rectangle[] ifdef::VK_NV_fill_rectangle[] * [[VUID-VkPipelineRasterizationStateCreateInfo-polygonMode-01507]] If the <> feature is not enabled, pname:polygonMode must: be ename:VK_POLYGON_MODE_FILL or ename:VK_POLYGON_MODE_FILL_RECTANGLE_NV * [[VUID-VkPipelineRasterizationStateCreateInfo-polygonMode-01414]] If the `<>` extension is not enabled, pname:polygonMode must: not be ename:VK_POLYGON_MODE_FILL_RECTANGLE_NV endif::VK_NV_fill_rectangle[] **** include::../validity/structs/VkPipelineRasterizationStateCreateInfo.txt[] -- [open,refpage='VkPipelineRasterizationStateCreateFlags',desc='Reserved for future use',type='flags'] -- include::../api/flags/VkPipelineRasterizationStateCreateFlags.txt[] tname:VkPipelineRasterizationStateCreateFlags is a bitmask type for setting a mask, but is currently reserved for future use. -- [open,refpage='VkPipelineMultisampleStateCreateInfo',desc='Structure specifying parameters of a newly created pipeline multisample state',type='structs'] -- The sname:VkPipelineMultisampleStateCreateInfo structure is defined as: include::../api/structs/VkPipelineMultisampleStateCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:rasterizationSamples is a elink:VkSampleCountFlagBits specifying the number of samples used in rasterization. * pname:sampleShadingEnable can: be used to enable <>. * pname:minSampleShading specifies a minimum fraction of sample shading if pname:sampleShadingEnable is set to ename:VK_TRUE. * pname:pSampleMask is a bitmask of static coverage information that is ANDed with the coverage information generated during rasterization, as described in <>. * pname:alphaToCoverageEnable controls whether a temporary coverage value is generated based on the alpha component of the fragment's first color output as specified in the <> section. * pname:alphaToOneEnable controls whether the alpha component of the fragment's first color output is replaced with one as described in <>. .Valid Usage **** * [[VUID-VkPipelineMultisampleStateCreateInfo-sampleShadingEnable-00784]] If the <> feature is not enabled, pname:sampleShadingEnable must: be ename:VK_FALSE * [[VUID-VkPipelineMultisampleStateCreateInfo-alphaToOneEnable-00785]] If the <> feature is not enabled, pname:alphaToOneEnable must: be ename:VK_FALSE * [[VUID-VkPipelineMultisampleStateCreateInfo-minSampleShading-00786]] pname:minSampleShading must: be in the range [eq]#[0,1]# ifdef::VK_NV_framebuffer_mixed_samples[] * [[VUID-VkPipelineMultisampleStateCreateInfo-rasterizationSamples-01415]] If the `VK_NV_framebuffer_mixed_samples` extension is enabled, and if the subpass has any color attachments and pname:rasterizationSamples is greater than the number of color samples, then pname:sampleShadingEnable must: be ename:VK_FALSE endif::VK_NV_framebuffer_mixed_samples[] **** include::../validity/structs/VkPipelineMultisampleStateCreateInfo.txt[] -- [open,refpage='VkPipelineMultisampleStateCreateFlags',desc='Reserved for future use',type='flags'] -- include::../api/flags/VkPipelineMultisampleStateCreateFlags.txt[] tname:VkPipelineMultisampleStateCreateFlags is a bitmask type for setting a mask, but is currently reserved for future use. -- Rasterization only generates fragments which cover one or more pixels inside the framebuffer. Pixels outside the framebuffer are never considered covered in the fragment. Fragments which would be produced by application of any of the primitive rasterization rules described below but which lie outside the framebuffer are not produced, nor are they processed by any later stage of the pipeline, including any of the early per-fragment tests described in <>. Surviving fragments are processed by fragment shaders. Fragment shaders determine associated data for fragments, and can: also modify or replace their assigned depth values. When the `VK_AMD_mixed_attachment_samples` and `VK_NV_framebuffer_mixed_samples` extensions are not enabled, if the subpass for which this pipeline is being created uses color and/or depth/stencil attachments, then pname:rasterizationSamples must: be the same as the sample count for those subpass attachments. ifdef::VK_AMD_mixed_attachment_samples[] When the `VK_AMD_mixed_attachment_samples` extension is enabled, if the subpass for which this pipeline is being created uses color and/or depth/stencil attachments, then pname:rasterizationSamples must: be the same as the maximum of the sample counts of those subpass attachments. endif::VK_AMD_mixed_attachment_samples[] ifdef::VK_NV_framebuffer_mixed_samples[] When the `VK_NV_framebuffer_mixed_samples` extension is enabled, pname:rasterizationSamples must: match the sample count of the depth/stencil attachment if present, otherwise must: be greater than or equal to the sample count of the color attachments, if present. endif::VK_NV_framebuffer_mixed_samples[] If the subpass for which this pipeline is being created does not use color or depth/stencil attachments, pname:rasterizationSamples must: follow the rules for a <>. [[primsrast-discard]] == Discarding Primitives Before Rasterization Primitives are discarded before rasterization if the pname:rasterizerDiscardEnable member of slink:VkPipelineRasterizationStateCreateInfo is enabled. When enabled, primitives are discarded after they are processed by the last active shader stage in the pipeline before rasterization. ifdef::VK_EXT_transform_feedback[] [[primsrast-stream]] == Controlling the Vertex Stream Used for Rasterization By default vertex data output from the last vertex processing stage are directed to vertex stream zero. Geometry shaders can: emit primitives to multiple independent vertex streams. Each vertex emitted by the geometry shader is directed at one of the vertex streams. As vertices are received on each vertex stream, they are arranged into primitives of the type specified by the geometry shader output primitive type. The shading language instructions code:OpEndPrimitive and code:OpEndStreamPrimitive can: be used to end the primitive being assembled on a given vertex stream and start a new empty primitive of the same type. An implementation supports up to sname:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:maxTransformFeedbackStreams streams, which is at least 1. The individual streams are numbered 0 through pname:maxTransformFeedbackStreams minus 1. There is no requirement on the order of the streams to which vertices are emitted, and the number of vertices emitted to each vertex stream can: be completely independent, subject only to the sname:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:maxTransformFeedbackStreamDataSize and sname:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:maxTransformFeedbackBufferDataSize limits. The primitives output from all vertex streams are passed to the transform feedback stage to be captured to transform feedback buffers in the manner specified by the last vertex processing stage shader's code:XfbBuffer, code:XfbStride, and code:Offsets decorations on the output interface variables in the graphics pipeline. To use a vertex stream other than zero, or to use multiple streams, the code:GeometryStreams capability must: be specified. By default, the primitives output from vertex stream zero are rasterized. If the implementation supports the slink:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:transformFeedbackRasterizationStreamSelect property it is possible to rasterize a vertex stream other than zero. By default, geometry shaders that emit vertices to multiple vertex streams are limited to using only the code:OutputPoints output primitive type. If the implementation supports the slink:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:transformFeedbackStreamsLinesTriangles property it is possible to emit code:OutputLineStrip or code:OutputTriangleStrip in addition to code:OutputPoints. [open,refpage='VkPipelineRasterizationStateStreamCreateInfoEXT',desc='Structure defining the geometry stream used for rasterization',type='structs'] -- The vertex stream used for rasterization is specified by adding a sname:VkPipelineRasterizationStateStreamCreateInfoEXT structure to the pname:pNext chain of a slink:VkPipelineRasterizationStateCreateInfo structure. The sname:VkPipelineRasterizationStateStreamCreateInfoEXT structure is defined as: include::../api/structs/VkPipelineRasterizationStateStreamCreateInfoEXT.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:rasterizationStream is the vertex stream selected for rasterization. If this structure is not present, pname:rasterizationStream is assumed to be zero. .Valid Usage **** * [[VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-geometryStreams-02324]] sname:VkPhysicalDeviceTransformFeedbackFeaturesEXT::pname:geometryStreams must: be enabled * [[VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-rasterizationStream-02325]] pname:rasterizationStream must: be less than slink:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:maxTransformFeedbackStreams * [[VUID-VkPipelineRasterizationStateStreamCreateInfoEXT-rasterizationStream-02326]] pname:rasterizationStream must: be zero if sname:VkPhysicalDeviceTransformFeedbackPropertiesEXT::pname:transformFeedbackRasterizationStreamSelect is ename:VK_FALSE **** include::../validity/structs/VkPipelineRasterizationStateStreamCreateInfoEXT.txt[] -- [open,refpage='VkPipelineRasterizationStateStreamCreateFlagsEXT',desc='Reserved for future use',type='flags'] -- include::../api/flags/VkPipelineRasterizationStateStreamCreateFlagsEXT.txt[] tname:VkPipelineRasterizationStateStreamCreateFlagsEXT is a bitmask type for setting a mask, but is currently reserved for future use. -- endif::VK_EXT_transform_feedback[] [[primrast-order]] == Rasterization Order Within a subpass of a <>, for a given (x,y,layer,sample) sample location, the following operations are guaranteed to execute in _rasterization order_, for each separate primitive that includes that sample location: . <> ifdef::VK_NV_scissor_exclusive[] . <> endif::VK_NV_scissor_exclusive[] . <> . <> . <> . <> . <> for <> ifdef::VK_NV_fragment_coverage_to_color[] . <> endif::VK_NV_fragment_coverage_to_color[] . <> . <>, <>, and color writes Each of these operations is atomically executed for each primitive and sample location. Execution of these operations for each primitive in a subpass occurs in ifndef::VK_AMD_rasterization_order[] <>. endif::VK_AMD_rasterization_order[] ifdef::VK_AMD_rasterization_order[] an order determined by the application. [open,refpage='VkPipelineRasterizationStateRasterizationOrderAMD',desc='Structure defining rasterization order for a graphics pipeline',type='structs'] -- The rasterization order to use for a graphics pipeline is specified by adding a sname:VkPipelineRasterizationStateRasterizationOrderAMD structure to the pname:pNext chain of a slink:VkPipelineRasterizationStateCreateInfo structure. The sname:VkPipelineRasterizationStateRasterizationOrderAMD structure is defined as: include::../api/structs/VkPipelineRasterizationStateRasterizationOrderAMD.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:rasterizationOrder is a elink:VkRasterizationOrderAMD value specifying the primitive rasterization order to use. include::../validity/structs/VkPipelineRasterizationStateRasterizationOrderAMD.txt[] If the `<>` device extension is not enabled or the application does not request a particular rasterization order through specifying a sname:VkPipelineRasterizationStateRasterizationOrderAMD structure then the rasterization order used by the graphics pipeline defaults to ename:VK_RASTERIZATION_ORDER_STRICT_AMD. -- [open,refpage='VkRasterizationOrderAMD',desc='Specify rasterization order for a graphics pipeline',type='enums'] -- Possible values of slink:VkPipelineRasterizationStateRasterizationOrderAMD::pname:rasterizationOrder, specifying the primitive rasterization order, are: include::../api/enums/VkRasterizationOrderAMD.txt[] * ename:VK_RASTERIZATION_ORDER_STRICT_AMD specifies that operations for each primitive in a subpass must: occur in <>. * ename:VK_RASTERIZATION_ORDER_RELAXED_AMD specifies that operations for each primitive in a subpass may: not occur in <>. -- endif::VK_AMD_rasterization_order[] [[primsrast-multisampling]] == Multisampling Multisampling is a mechanism to antialias all Vulkan primitives: points, lines, and polygons. The technique is to sample all primitives multiple times at each pixel. Each sample in each framebuffer attachment has storage for a color, depth, and/or stencil value, such that per-fragment operations apply to each sample independently. The color sample values can: be later _resolved_ to a single color (see <> and the <> chapter for more details on how to resolve multisample images to non-multisample images). Vulkan defines rasterization rules for single-sample modes in a way that is equivalent to a multisample mode with a single sample in the center of each fragment. Each fragment includes a coverage value with pname:rasterizationSamples bits (see <>). Each fragment includes pname:rasterizationSamples depth values and sets of associated data. An implementation may: choose to assign the same associated data to more than one sample. The location for evaluating such associated data may: be anywhere within the fragment area including the fragment's center location [eq]#(x~f~,y~f~)# or any of the sample locations. When pname:rasterizationSamples is ename:VK_SAMPLE_COUNT_1_BIT, the fragment's center location must: be used. The different associated data values need not all be evaluated at the same location. Each fragment thus consists of integer x and y grid coordinates, pname:rasterizationSamples depth values and sets of associated data, and a coverage value with pname:rasterizationSamples bits. It is understood that each pixel has pname:rasterizationSamples locations associated with it. These locations are exact positions, rather than regions or areas, and each is referred to as a sample point. The sample points associated with a pixel must: be located inside or on the boundary of the unit square that is considered to bound the pixel. Furthermore, the relative locations of sample points may: be identical for each pixel in the framebuffer, or they may: differ. ifdef::VK_EXT_fragment_density_map[] If the render pass has a fragment density map attachment, each fragment only has pname:rasterizationSamples locations associated with it regardless of how many pixels are covered in the fragment area. Fragment sample locations are defined as if the fragment had an area of [eq]#(1,1)# and its sample points must: be located within these bounds. Their actual location in the framebuffer is calculated by scaling the sample location by the fragment area. Attachments with storage for multiple samples per pixel are located at the pixel sample locations. Otherwise, the fragment's sample locations are generally used for evaluation of associated data and fragment operations. endif::VK_EXT_fragment_density_map[] If the current pipeline includes a fragment shader with one or more variables in its interface decorated with code:Sample and code:Input, the data associated with those variables will be assigned independently for each sample. The values for each sample must: be evaluated at the location of the sample. The data associated with any other variables not decorated with code:Sample and code:Input need not be evaluated independently for each sample. If the pname:standardSampleLocations member of slink:VkPhysicalDeviceLimits is ename:VK_TRUE, then the sample counts ename:VK_SAMPLE_COUNT_1_BIT, ename:VK_SAMPLE_COUNT_2_BIT, ename:VK_SAMPLE_COUNT_4_BIT, ename:VK_SAMPLE_COUNT_8_BIT, and ename:VK_SAMPLE_COUNT_16_BIT have sample locations as listed in the following table, with the [eq]##i##th entry in the table corresponding to bit [eq]#i# in the sample masks. ename:VK_SAMPLE_COUNT_32_BIT and ename:VK_SAMPLE_COUNT_64_BIT do not have standard sample locations. Locations are defined relative to an origin in the upper left corner of the fragment. <<< .Standard sample locations [align="center"] |==== |ename:VK_SAMPLE_COUNT_1_BIT|ename:VK_SAMPLE_COUNT_2_BIT|ename:VK_SAMPLE_COUNT_4_BIT|ename:VK_SAMPLE_COUNT_8_BIT|ename:VK_SAMPLE_COUNT_16_BIT | [eq]#(0.5,0.5)# | [eq]#(0.75,0.75)# + [eq]#(0.25,0.25)# | [eq]#(0.375, 0.125)# + [eq]#(0.875, 0.375)# + [eq]#(0.125, 0.625)# + [eq]#(0.625, 0.875)# | [eq]#(0.5625, 0.3125)# + [eq]#(0.4375, 0.6875)# + [eq]#(0.8125, 0.5625)# + [eq]#(0.3125, 0.1875)# + [eq]#(0.1875, 0.8125)# + [eq]#(0.0625, 0.4375)# + [eq]#(0.6875, 0.9375)# + [eq]#(0.9375, 0.0625)# | [eq]#(0.5625, 0.5625)# + [eq]#(0.4375, 0.3125)# + [eq]#(0.3125, 0.625)# + [eq]#(0.75, 0.4375)# + [eq]#(0.1875, 0.375)# + [eq]#(0.625, 0.8125)# + [eq]#(0.8125, 0.6875)# + [eq]#(0.6875, 0.1875)# + [eq]#(0.375, 0.875)# + [eq]#(0.5, 0.0625)# + [eq]#(0.25, 0.125)# + [eq]#(0.125, 0.75)# + [eq]#(0.0, 0.5)# + [eq]#(0.9375, 0.25)# + [eq]#(0.875, 0.9375)# + [eq]#(0.0625, 0.0)# |image:images/sample_count_1.svg[align="center",opts="{imageopts}"] |image:images/sample_count_2.svg[align="center",opts="{imageopts}"] |image:images/sample_count_4.svg[align="center",opts="{imageopts}"] |image:images/sample_count_8.svg[align="center",opts="{imageopts}"] |image:images/sample_count_16.svg[align="center",opts="{imageopts}"] |==== ifdef::VK_AMD_shader_fragment_mask[] Color images created with multiple samples per pixel use a compression technique where there are two arrays of data associated with each pixel. The first array contains one element per sample where each element stores an index to the second array defining the _fragment mask_ of the pixel. The second array contains one element per _color fragment_ and each element stores a unique color value in the format of the image. With this compression technique it's not always necessary to actually use unique storage locations for each color sample: when multiple samples share the same color value the fragment mask may: have two samples referring to the same color fragment. The number of color fragments is determined by the pname:samples member of the slink:VkImageCreateInfo structure used to create the image. The `<>` device extension provides shader instructions enabling the application to get direct access to the fragment mask and the individual color fragment values. [[vk-amd-shader-fragment-mask-diagram]] image::images/fragment_mask.svg[align="center",title="Fragment Mask",align="center",opts="{imageopts}"] endif::VK_AMD_shader_fragment_mask[] ifdef::VK_EXT_sample_locations[] [[primrast-samplelocations]] == Custom Sample Locations [open,refpage='VkPipelineSampleLocationsStateCreateInfoEXT',desc='Structure specifying sample locations for a pipeline',type='structs'] -- Applications can: also control the sample locations used for rasterization. If the pname:pNext chain of the slink:VkPipelineMultisampleStateCreateInfo structure specified at pipeline creation time includes an instance of the sname:VkPipelineSampleLocationsStateCreateInfoEXT structure, then that structure controls the sample locations used when rasterizing primitives with the pipeline. The sname:VkPipelineSampleLocationsStateCreateInfoEXT structure is defined as: include::../api/structs/VkPipelineSampleLocationsStateCreateInfoEXT.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:sampleLocationsEnable controls whether custom sample locations are used. If pname:sampleLocationsEnable is ename:VK_FALSE, the default sample locations are used and the values specified in pname:sampleLocationsInfo are ignored. * pname:sampleLocationsInfo is the sample locations to use during rasterization if pname:sampleLocationsEnable is ename:VK_TRUE and the graphics pipeline is not created with ename:VK_DYNAMIC_STATE_SAMPLE_LOCATIONS_EXT. include::../validity/structs/VkPipelineSampleLocationsStateCreateInfoEXT.txt[] -- [open,refpage='VkSampleLocationsInfoEXT',desc='Structure specifying a set of sample locations',type='structs'] -- The sname:VkSampleLocationsInfoEXT structure is defined as: include::../api/structs/VkSampleLocationsInfoEXT.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:sampleLocationsPerPixel is a elink:VkSampleCountFlagBits specifying the number of sample locations per pixel. * pname:sampleLocationGridSize is the size of the sample location grid to select custom sample locations for. * pname:sampleLocationsCount is the number of sample locations in pname:pSampleLocations. * pname:pSampleLocations is an array of pname:sampleLocationsCount slink:VkSampleLocationEXT structures. This structure can: be used either to specify the sample locations to be used for rendering or to specify the set of sample locations an image subresource has been last rendered with for the purposes of layout transitions of depth/stencil images created with ename:VK_IMAGE_CREATE_SAMPLE_LOCATIONS_COMPATIBLE_DEPTH_BIT_EXT. The sample locations in pname:pSampleLocations specify pname:sampleLocationsPerPixel number of sample locations for each pixel in the grid of the size specified in pname:sampleLocationGridSize. The sample location for sample [eq]#i# at the pixel grid location [eq]#(x,y)# is taken from [eq]#pname:pSampleLocations[(x + y * pname:sampleLocationGridSize.width) * pname:sampleLocationsPerPixel + i]#. ifdef::VK_EXT_fragment_density_map[] If the render pass has a fragment density map, the implementation will choose the sample locations for the fragment and the contents of pname:pSampleLocations may: be ignored. endif::VK_EXT_fragment_density_map[] .Valid Usage **** * [[VUID-VkSampleLocationsInfoEXT-sampleLocationsPerPixel-01526]] pname:sampleLocationsPerPixel must: be a bit value that is set in slink:VkPhysicalDeviceSampleLocationsPropertiesEXT::pname:sampleLocationSampleCounts * [[VUID-VkSampleLocationsInfoEXT-sampleLocationsCount-01527]] pname:sampleLocationsCount must: equal [eq]#pname:sampleLocationsPerPixel {times} pname:sampleLocationGridSize.width {times} pname:sampleLocationGridSize.height# **** include::../validity/structs/VkSampleLocationsInfoEXT.txt[] -- [open,refpage='VkSampleLocationEXT',desc='Structure specifying the coordinates of a sample location',type='structs'] -- The sname:VkSampleLocationEXT structure is defined as: include::../api/structs/VkSampleLocationEXT.txt[] * pname:x is the horizontal coordinate of the sample's location. * pname:y is the vertical coordinate of the sample's location. The domain space of the sample location coordinates has an upper-left origin within the pixel in framebuffer space. The values specified in a sname:VkSampleLocationEXT structure are always clamped to the implementation-dependent sample location coordinate range [eq]#[pname:sampleLocationCoordinateRange[0],pname:sampleLocationCoordinateRange[1]]# that can: be queried by chaining the slink:VkPhysicalDeviceSampleLocationsPropertiesEXT structure to the pname:pNext chain of slink:VkPhysicalDeviceProperties2. include::../validity/structs/VkSampleLocationEXT.txt[] -- [open,refpage='vkCmdSetSampleLocationsEXT',desc='Set the dynamic sample locations state',type='protos'] -- The custom sample locations used for rasterization when sname:VkPipelineSampleLocationsStateCreateInfoEXT::pname:sampleLocationsEnable is ename:VK_TRUE are specified by the sname:VkPipelineSampleLocationsStateCreateInfoEXT::pname:sampleLocationsInfo property of the bound graphics pipeline, if the pipeline was not created with ename:VK_DYNAMIC_STATE_SAMPLE_LOCATIONS_EXT enabled. Otherwise, the sample locations used for rasterization are set by calling fname:vkCmdSetSampleLocationsEXT: include::../api/protos/vkCmdSetSampleLocationsEXT.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:pSampleLocationsInfo is the sample locations state to set. .Valid Usage **** * [[VUID-vkCmdSetSampleLocationsEXT-None-01528]] The bound graphics pipeline must: have been created with the ename:VK_DYNAMIC_STATE_SAMPLE_LOCATIONS_EXT dynamic state enabled * [[VUID-vkCmdSetSampleLocationsEXT-sampleLocationsPerPixel-01529]] The pname:sampleLocationsPerPixel member of pname:pSampleLocationsInfo must: equal the pname:rasterizationSamples member of the slink:VkPipelineMultisampleStateCreateInfo structure the bound graphics pipeline has been created with * [[VUID-vkCmdSetSampleLocationsEXT-variableSampleLocations-01530]] If slink:VkPhysicalDeviceSampleLocationsPropertiesEXT::pname:variableSampleLocations is ename:VK_FALSE then the current render pass must: have been begun by specifying a slink:VkRenderPassSampleLocationsBeginInfoEXT structure whose pname:pPostSubpassSampleLocations member contains an element with a pname:subpassIndex matching the current subpass index and the pname:sampleLocationsInfo member of that element must: match the sample locations state pointed to by pname:pSampleLocationsInfo **** include::../validity/protos/vkCmdSetSampleLocationsEXT.txt[] -- endif::VK_EXT_sample_locations[] ifdef::VK_NV_shading_rate_image[] [[primsrast-shading-rate-image]] == Shading Rate Image The <> feature allows pipelines to use a <> to control the <> and the minimum number of fragment shader invocations launched for each fragment. When the shading rate image is enabled, the rasterizer determines a base <> for each region of the framebuffer covered by a primitive by fetching a value from the shading rate image and translating it to a shading rate using a per-viewport shading rate palette. This base shading rate is then adjusted to derive a final shading rate, which specifies the fragment area and fragment shader invocation count to use for fragments generated in the region. [open,refpage='VkPipelineViewportShadingRateImageStateCreateInfoNV',desc='Structure specifying parameters controlling shading rate image usage',type='structs'] -- If the pname:pNext chain of slink:VkPipelineViewportStateCreateInfo includes a sname:VkPipelineViewportShadingRateImageStateCreateInfoNV structure, then that structure includes parameters that control the shading rate. The sname:VkPipelineViewportShadingRateImageStateCreateInfoNV structure is defined as: include::../api/structs/VkPipelineViewportShadingRateImageStateCreateInfoNV.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:shadingRateImageEnable specifies whether shading rate image and palettes are used during rasterization. * pname:viewportCount specifies the number of per-viewport palettes used to translate values stored in shading rate images. * pname:pShadingRatePalettes is a pointer to an array of slink:VkShadingRatePaletteNV structures defining the palette for each viewport. If the shading rate palette state is dynamic, this member is ignored. If this structure is not present, pname:shadingRateImageEnable is considered to be ename:VK_FALSE, and the shading rate image and palettes are not used. .Valid Usage **** * [[VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-viewportCount-02054]] If the <> feature is not enabled, pname:viewportCount must: be `0` or `1` * [[VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-viewportCount-02055]] pname:viewportCount must: be less than or equal to sname:VkPhysicalDeviceLimits::pname:maxViewports * [[VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-shadingRateImageEnable-02056]] If pname:shadingRateImageEnable is ename:VK_TRUE, pname:viewportCount must: be equal to the pname:viewportCount member of sname:VkPipelineViewportStateCreateInfo * [[VUID-VkPipelineViewportShadingRateImageStateCreateInfoNV-pDynamicStates-02057]] If no element of the pname:pDynamicStates member of pname:pDynamicState is ename:VK_DYNAMIC_STATE_VIEWPORT_SHADING_RATE_PALETTE_NV, pname:pShadingRatePalettes must: be a valid pointer to an array of pname:viewportCount sname:VkShadingRatePaletteNV structures **** include::../validity/structs/VkPipelineViewportShadingRateImageStateCreateInfoNV.txt[] -- [open,refpage='vkCmdBindShadingRateImageNV',desc='Bind a shading rate image on a command buffer',type='protos'] -- When shading rate image usage is enabled in the bound pipeline, the pipeline uses a shading rate image specified by the command: include::../api/protos/vkCmdBindShadingRateImageNV.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:imageView is an image view handle that specifies the shading rate image. pname:imageView may: be set to dlink:VK_NULL_HANDLE, which is equivalent to specifying a view of an image filled with zero values. * pname:imageLayout is the layout that the image subresources accessible from pname:imageView will be in when the shading rate image is accessed. .Valid Usage **** * [[VUID-vkCmdBindShadingRateImageNV-None-02058]] The <> feature must: be enabled. * [[VUID-vkCmdBindShadingRateImageNV-imageView-02059]] If pname:imageView is not dlink:VK_NULL_HANDLE, it must: be a valid slink:VkImageView handle of type ename:VK_IMAGE_VIEW_TYPE_2D or ename:VK_IMAGE_VIEW_TYPE_2D_ARRAY. * [[VUID-vkCmdBindShadingRateImageNV-imageView-02060]] If pname:imageView is not dlink:VK_NULL_HANDLE, it must: have a format of ename:VK_FORMAT_R8_UINT. * [[VUID-vkCmdBindShadingRateImageNV-imageView-02061]] If pname:imageView is not dlink:VK_NULL_HANDLE, it must: have been created with a pname:usage value including ename:VK_IMAGE_USAGE_SHADING_RATE_IMAGE_BIT_NV * [[VUID-vkCmdBindShadingRateImageNV-imageView-02062]] If pname:imageView is not dlink:VK_NULL_HANDLE, pname:imageLayout must: match the actual elink:VkImageLayout of each subresource accessible from pname:imageView at the time the subresource is accessed. * [[VUID-vkCmdBindShadingRateImageNV-imageLayout-02063]] If pname:imageView is not dlink:VK_NULL_HANDLE, pname:imageLayout must: be ename:VK_IMAGE_LAYOUT_SHADING_RATE_OPTIMAL_NV or ename:VK_IMAGE_LAYOUT_GENERAL. **** include::../validity/protos/vkCmdBindShadingRateImageNV.txt[] -- When the shading rate image is enabled in the current pipeline, rasterizing a primitive covering the pixel with coordinates (_x_,_y_) will fetch a shading rate index value from the shading rate image bound by fname:vkCmdBindShadingRateImageNV. If the shading rate image view has a type of ename:VK_IMAGE_VIEW_TYPE_2D, the lookup will use texel coordinates (_u_,_v_) where latexmath:[u = \lfloor \frac{x}{twidth} \rfloor], latexmath:[v = \lfloor \frac{y}{theight} \rfloor], and latexmath:[twidth] and latexmath:[theight] are the width and height of the implementation-dependent <>. If the shading rate image view has a type of ename:VK_IMAGE_VIEW_TYPE_2D_ARRAY, the lookup will use texel coordinates (_u_,_v_) to extract a texel from the layer _l_, where _l_ is the layer of the framebuffer being rendered to. If _l_ is greater than or equal to the number of layers in the image view, layer zero will be used. If the bound shading rate image view is not dlink:VK_NULL_HANDLE and contains a texel with coordinates (_u_,_v_) in layer _l_ (if applicable), the single unsigned integer component for that texel will be used as the shading rate index. If the (_u_,_v_) coordinate is outside the extents of the subresource used by the shading rate image view, or if the image view is dlink:VK_NULL_HANDLE, the shading rate index is zero. If the shading rate image view has multiple mipmap levels, the base level identified by sname:VkImageSubresourceRange::pname:baseMipLevel will be used. A shading rate index is mapped to a base shading rate using a lookup table called the shading rate image palette. There is a separate palette for each viewport. The number of entries in each palette is given by the implementation-dependent <>. [open,refpage='vkCmdSetViewportShadingRatePaletteNV',desc='Set shading rate image palettes on a command buffer',type='protos'] -- If a pipeline state object is created with ename:VK_DYNAMIC_STATE_VIEWPORT_SHADING_RATE_PALETTE_NV enabled, the per-viewport shading rate image palettes are set by the command: include::../api/protos/vkCmdSetViewportShadingRatePaletteNV.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:firstViewport is the index of the first viewport whose shading rate palette is updated by the command. * pname:viewportCount is the number of viewports whose shading rate palettes are updated by the command. * pname:pShadingRatePalettes is a pointer to an array of slink:VkShadingRatePaletteNV structures defining the palette for each viewport. .Valid Usage **** * [[VUID-vkCmdSetViewportShadingRatePaletteNV-None-02064]] The <> feature must: be enabled. * [[VUID-vkCmdSetViewportShadingRatePaletteNV-None-02065]] The bound graphics pipeline must: have been created with the ename:VK_DYNAMIC_STATE_VIEWPORT_SHADING_RATE_PALETTE_NV dynamic state enabled * [[VUID-vkCmdSetViewportShadingRatePaletteNV-firstViewport-02066]] pname:firstViewport must: be less than sname:VkPhysicalDeviceLimits::pname:maxViewports * [[VUID-vkCmdSetViewportShadingRatePaletteNV-firstViewport-02067]] The sum of pname:firstViewport and pname:viewportCount must: be between `1` and sname:VkPhysicalDeviceLimits::pname:maxViewports, inclusive * [[VUID-vkCmdSetViewportShadingRatePaletteNV-firstViewport-02068]] If the <> feature is not enabled, pname:firstViewport must: be `0` * [[VUID-vkCmdSetViewportShadingRatePaletteNV-viewportCount-02069]] If the <> feature is not enabled, pname:viewportCount must: be `1` **** include::../validity/protos/vkCmdSetViewportShadingRatePaletteNV.txt[] -- [open,refpage='VkShadingRatePaletteNV',desc='Structure specifying a single shading rate palette',type='structs'] -- The sname:VkShadingRatePaletteNV structure specifies to contents of a single shading rate image palette and is defined as: include::../api/structs/VkShadingRatePaletteNV.txt[] * pname:shadingRatePaletteEntryCount specifies the number of entries in the shading rate image palette. * pname:pShadingRatePaletteEntries is a pointer to an array of elink:VkShadingRatePaletteEntryNV enums defining the shading rate for each palette entry. .Valid Usage **** * [[VUID-VkShadingRatePaletteNV-shadingRatePaletteEntryCount-02071]] pname:shadingRatePaletteEntryCount must: be between `1` and sname:VkPhysicalDeviceShadingRateImagePropertiesNV::pname:shadingRatePaletteSize, inclusive **** include::../validity/structs/VkShadingRatePaletteNV.txt[] -- To determine the base shading rate image, a shading rate index _i_ is mapped to array element _i_ in the array pname:pShadingRatePaletteEntries for the palette corresponding to the viewport used for the fragment. If _i_ is greater than or equal to the palette size pname:shadingRatePaletteEntryCount, the base shading rate is undefined. [open,refpage='VkShadingRatePaletteEntryNV',desc='Shading rate image palette entry types',type='enums'] -- The supported shading rate image palette entries are defined by elink:VkShadingRatePaletteEntryNV: include::../api/enums/VkShadingRatePaletteEntryNV.txt[] The following table indicates the width and height (in pixels) of each fragment generated using the indicated shading rate, as well as the maximum number of fragment shader invocations launched for each fragment. When processing regions of a primitive that have a shading rate of ename:VK_SHADING_RATE_PALETTE_ENTRY_NO_INVOCATIONS_NV, no fragments will be generated in that region. [options="header"] |======== | Shading Rate | Width | Height | Invocations | ename:VK_SHADING_RATE_PALETTE_ENTRY_NO_INVOCATIONS_NV | 0 | 0 | 0 | ename:VK_SHADING_RATE_PALETTE_ENTRY_16_INVOCATIONS_PER_PIXEL_NV | 1 | 1 | 16 | ename:VK_SHADING_RATE_PALETTE_ENTRY_8_INVOCATIONS_PER_PIXEL_NV | 1 | 1 | 8 | ename:VK_SHADING_RATE_PALETTE_ENTRY_4_INVOCATIONS_PER_PIXEL_NV | 1 | 1 | 4 | ename:VK_SHADING_RATE_PALETTE_ENTRY_2_INVOCATIONS_PER_PIXEL_NV | 1 | 1 | 2 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_PIXEL_NV | 1 | 1 | 1 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X1_PIXELS_NV | 2 | 1 | 1 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_1X2_PIXELS_NV | 1 | 2 | 1 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X2_PIXELS_NV | 2 | 2 | 1 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_4X2_PIXELS_NV | 4 | 2 | 1 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_2X4_PIXELS_NV | 2 | 4 | 1 | ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_4X4_PIXELS_NV | 4 | 4 | 1 |======== -- When the shading rate image is disabled, a shading rate of ename:VK_SHADING_RATE_PALETTE_ENTRY_1_INVOCATION_PER_PIXEL_NV will be used as the base shading rate. Once a base shading rate has been established, it is adjusted to produce a final shading rate. First, if the base shading rate uses multiple pixels for each fragment, the implementation may: reduce the fragment area to ensure that the total number of coverage samples for all pixels in a fragment does not exceed <>. If <> is active in the current pipeline and would result in processing _n_ (_n_ > 1) unique samples per fragment when the shading rate image is disabled, the shading rate is adjusted in an implementation-dependent manner to increase the number of fragment shader invocations spawned by the primitive. If the shading rate indicates _fs_ pixels per fragment and _fs_ is greater than _n_, the fragment area is adjusted so each fragment has approximately latexmath:[fs \over n] pixels. Otherwise, if the shading rate indicates _ipf_ invocations per fragment, the fragment area will be adjusted to a single pixel with approximately latexmath:[ipf \times n \over fs] invocations per fragment. If sample shading occurs due to the use of a fragment shader input variable decorated with code:SampleId or code:SamplePosition, the shading rate is ignored. Each fragment will have a single pixel and will spawn up to code:totalSamples fragment shader invocations, as when using <> without a shading rate image. Finally, if the shading rate specifies multiple fragment shader invocations per fragment, the total number of invocations in the shading rate is clamped to be no larger than the value of code:totalSamples used for <>. When the final shading rate for a primitive covering pixel (_x_,_y_) has a fragment area of latexmath:[fw \times fh], the fragment for that pixel will cover all pixels with coordinates (_x_',_y_') that satisfy the equations: [latexmath] +++++++++++++++++++ \begin{aligned} \lfloor \frac{x}{fw} \rfloor == \lfloor \frac{x'}{fw} \rfloor \end{aligned} +++++++++++++++++++ [latexmath] +++++++++++++++++++ \begin{aligned} \lfloor \frac{y}{fh} \rfloor == \lfloor \frac{y'}{fh} \rfloor \end{aligned} +++++++++++++++++++ This combined fragment is considered to have multiple coverage samples; the total number of samples in this fragment is given by latexmath:[samples = fw \times fh \times rs] where _rs_ indicates the value of sname:VkPipelineMultisampleStateCreateInfo::pname:rasterizationSamples specified at pipeline creation time. The set of coverage samples in the fragment is the union of the per-pixel coverage samples in each of the fragment's pixels The location and order of coverage samples within each pixel in the combined fragment are assigned as described in ifndef::VK_EXT_sample_locations[] <>. endif::VK_EXT_sample_locations[] ifdef::VK_EXT_sample_locations[] <> and <>. endif::VK_EXT_sample_locations[] Each coverage sample in the set of pixels belonging to the combined fragment is assigned a unique sample number in the range [0,_samples_-1]. If the <> feature is supported, the order of coverage samples can: be specified for each combination of fragment area and coverage sample count. If this feature is not supported, the sample order is implementation-dependent. [open,refpage='VkPipelineViewportCoarseSampleOrderStateCreateInfoNV',desc='Structure specifying parameters controlling sample order in coarse fragments',type='structs'] -- If the pname:pNext chain of slink:VkPipelineViewportStateCreateInfo includes a sname:VkPipelineViewportCoarseSampleOrderStateCreateInfoNV structure, then that structure includes parameters that control the order of coverage samples in fragments larger than one pixel. The sname:VkPipelineViewportCoarseSampleOrderStateCreateInfoNV structure is defined as: include::../api/structs/VkPipelineViewportCoarseSampleOrderStateCreateInfoNV.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:sampleOrderType specifies the mechanism used to order coverage samples in fragments larger than one pixel. * pname:customSampleOrderCount specifies the number of custom sample orderings to use when ordering coverage samples. * pname:pCustomSampleOrders is a pointer to an array of slink:VkCoarseSampleOrderCustomNV structures, each of which specifies the coverage sample order for a single combination of fragment area and coverage sample count. If this structure is not present, pname:sampleOrderType is considered to be ename:VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV. If pname:sampleOrderType is ename:VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV, the coverage sample order used for any combination of fragment area and coverage sample count not enumerated in pname:pCustomSampleOrders will be identical to that used for ename:VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV. If the pipeline was created with ename:VK_DYNAMIC_STATE_VIEWPORT_COARSE_SAMPLE_ORDER_NV, the contents of this structure (if present) are ignored, and the coverage sample order is instead specified by flink:vkCmdSetCoarseSampleOrderNV. .Valid Usage **** * [[VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-sampleOrderType-02072]] If pname:sampleOrderType is not ename:VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV, pname:customSamplerOrderCount must: be `0` * [[VUID-VkPipelineViewportCoarseSampleOrderStateCreateInfoNV-pCustomSampleOrders-02234]] The array pname:pCustomSampleOrders must: not contain two structures with matching values for both the pname:shadingRate and pname:sampleCount members. **** include::../validity/structs/VkPipelineViewportCoarseSampleOrderStateCreateInfoNV.txt[] -- [open,refpage='VkCoarseSampleOrderTypeNV',desc='Shading rate image sample ordering types',type='enums'] -- The type elink:VkCoarseSampleOrderTypeNV specifies the technique used to order coverage samples in fragments larger than one pixel, and is defined as: include::../api/enums/VkCoarseSampleOrderTypeNV.txt[] * ename:VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV specifies that coverage samples will be ordered in an implementation-dependent manner. * ename:VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV specifies that coverage samples will be ordered according to the array of custom orderings provided in either the pname:pCustomSampleOrders member of sname:VkPipelineViewportCoarseSampleOrderStateCreateInfoNV or the pname:pCustomSampleOrders member of flink:vkCmdSetCoarseSampleOrderNV. * ename:VK_COARSE_SAMPLE_ORDER_TYPE_PIXEL_MAJOR_NV specifies that coverage samples will be ordered sequentially, sorted first by pixel coordinate (in row-major order) and then by coverage sample number. * ename:VK_COARSE_SAMPLE_ORDER_TYPE_SAMPLE_MAJOR_NV specifies that coverage samples will be ordered sequentially, sorted first by coverage sample number and then by pixel coordinate (in row-major order). -- When using a coarse sample order of ename:VK_COARSE_SAMPLE_ORDER_TYPE_PIXEL_MAJOR_NV for a fragment with an upper-left corner of latexmath:[(fx,fy)] with a width of latexmath:[fw \times fh] and latexmath:[fsc] coverage samples per pixel, sample latexmath:[cs] of the fragment will be assigned to sample latexmath:[fs] of pixel latexmath:[(px,py)] will be assigned as follows: [latexmath] +++++++++++++++++++ \begin{aligned} px = & fx + (\lfloor {cs \over fsc} \rfloor \text{ \% } fw) \\ py = & fy + \lfloor {cs \over {fsc \times fw}} \rfloor \\ fs = & cs \text{ \% } fsc \end{aligned} +++++++++++++++++++ When using a coarse sample order of ename:VK_COARSE_SAMPLE_ORDER_TYPE_SAMPLE_MAJOR_NV, sample latexmath:[cs] will be assigned as follows: [latexmath] +++++++++++++++++++ \begin{aligned} px = & fx + cs \text{ \% } fw \\ py = & (fy + \lfloor {cs \over fw} \rfloor \text{ \% } fh) \\ fs = & \lfloor {cs \over {fw \times fh}} \rfloor \end{aligned} +++++++++++++++++++ [open,refpage='VkCoarseSampleOrderCustomNV',desc='Structure specifying parameters controlling shading rate image usage',type='structs'] -- The sname:VkCoarseSampleOrderCustomNV structure is used with a coverage sample ordering type of ename:VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV to specify the order of coverage samples for one combination of fragment width, fragment height, and coverage sample count. The structure is defined as: include::../api/structs/VkCoarseSampleOrderCustomNV.txt[] * pname:shadingRate is a shading rate palette entry that identifies the fragment width and height for the combination of fragment area and per-pixel coverage sample count to control. * pname:sampleCount identifies the per-pixel coverage sample count for the combination of fragment area and coverage sample count to control. * pname:sampleLocationCount specifies the number of sample locations in the custom ordering. * pname:pSampleLocations is a pointer to an array of slink:VkCoarseSampleOrderCustomNV structures that specifies the location of each sample in the custom ordering. When using a custom sample ordering, element _i_ in pname:pSampleLocations specifies a specific pixel and per-pixel coverage sample number that corresponds to the coverage sample numbered _i_ in the multi-pixel fragment. .Valid Usage **** * [[VUID-VkCoarseSampleOrderCustomNV-shadingRate-02073]] pname:shadingRate must: be a shading rate that generates fragments with more than one pixel. * [[VUID-VkCoarseSampleOrderCustomNV-sampleCount-02074]] pname:sampleCount must: correspond to a sample count enumerated in tlink:VkSampleCountFlags whose corresponding bit is set in slink:VkPhysicalDeviceLimits::pname:framebufferNoAttachmentsSampleCounts. * [[VUID-VkCoarseSampleOrderCustomNV-sampleLocationCount-02075]] pname:sampleLocationCount must: be equal to the product of pname:sampleCount, the fragment width for pname:shadingRate, and the fragment height for pname:shadingRate. * [[VUID-VkCoarseSampleOrderCustomNV-sampleLocationCount-02076]] pname:sampleLocationCount must: be less than or equal to the value of sname:VkPhysicalDeviceShadingRateImagePropertiesNV::pname:shadingRateMaxCoarseSamples. * [[VUID-VkCoarseSampleOrderCustomNV-pSampleLocations-02077]] The array pname:pSampleLocations must: contain exactly one entry for every combination of valid values for pname:pixelX, pname:pixelY, and pname:sample in the structure slink:VkCoarseSampleOrderCustomNV. **** include::../validity/structs/VkCoarseSampleOrderCustomNV.txt[] -- [open,refpage='VkCoarseSampleLocationNV',desc='Structure specifying parameters controlling shading rate image usage',type='structs'] -- The sname:VkCoarseSampleLocationNV structure identifies a specific pixel and sample number for one of the coverage samples in a fragment that is larger than one pixel. This structure is defined as: include::../api/structs/VkCoarseSampleLocationNV.txt[] * pname:pixelX is added to the x coordinate of the upper-leftmost pixel of each fragment to identify the pixel containing the coverage sample. * pname:pixelY is added to the y coordinate of the upper-leftmost pixel of each fragment to identify the pixel containing the coverage sample. * pname:sample is the number of the coverage sample in the pixel identified by pname:pixelX and pname:pixelY. .Valid Usage **** * [[VUID-VkCoarseSampleLocationNV-pixelX-02078]] pname:pixelX must: be less than the width (in pixels) of the fragment. * [[VUID-VkCoarseSampleLocationNV-pixelY-02079]] pname:pixelY must: be less than the height (in pixels) of the fragment. * [[VUID-VkCoarseSampleLocationNV-sample-02080]] pname:sample must: be less than the number of coverage samples in each pixel belonging to the fragment. **** include::../validity/structs/VkCoarseSampleLocationNV.txt[] -- [open,refpage='vkCmdSetCoarseSampleOrderNV',desc='Set sample order for coarse fragments on a command buffer',type='protos'] -- If a pipeline state object is created with ename:VK_DYNAMIC_STATE_VIEWPORT_COARSE_SAMPLE_ORDER_NV enabled, the order of coverage samples in fragments larger than one pixel is set by the command: include::../api/protos/vkCmdSetCoarseSampleOrderNV.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:sampleOrderType specifies the mechanism used to order coverage samples in fragments larger than one pixel. * pname:customSampleOrderCount specifies the number of custom sample orderings to use when ordering coverage samples. * pname:pCustomSampleOrders is a pointer to an array of slink:VkCoarseSampleOrderCustomNV structures, each of which specifies the coverage sample order for a single combination of fragment area and coverage sample count. If pname:sampleOrderType is ename:VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV, the coverage sample order used for any combination of fragment area and coverage sample count not enumerated in pname:pCustomSampleOrders will be identical to that used for ename:VK_COARSE_SAMPLE_ORDER_TYPE_DEFAULT_NV. .Valid Usage **** * [[VUID-vkCmdSetCoarseSampleOrderNV-sampleOrderType-02081]] If pname:sampleOrderType is not ename:VK_COARSE_SAMPLE_ORDER_TYPE_CUSTOM_NV, pname:customSamplerOrderCount must: be `0` * [[VUID-vkCmdSetCoarseSampleOrderNV-pCustomSampleOrders-02235]] The array pname:pCustomSampleOrders must: not contain two structures with matching values for both the pname:shadingRate and pname:sampleCount members. **** include::../validity/protos/vkCmdSetCoarseSampleOrderNV.txt[] -- If the final shading rate for a primitive covering pixel (_x_,_y_) results in _n_ invocations per pixel (_n_ > 1), _n_ separate fragment shader invocations will be generated for the fragment. Each coverage sample in the fragment will be assigned to one of the _n_ fragment shader invocations in an implementation-dependent manner. The outputs from the <> of each shader invocation will be broadcast to all of the framebuffer samples associated with the invocation. If none of the coverage samples associated with a fragment shader invocation is covered by a primitive, the implementation may: discard the fragment shader invocation for those samples. If the final shading rate for a primitive covering pixel (_x_,_y_) results in a fragment containing multiple pixels, a single set of fragment shader invocations will be generated for all pixels in the combined fragment. Outputs from the <> will be broadcast to all covered framebuffer samples belonging to the fragment. If the fragment shader executes code discarding the fragment, none of the samples of the fragment will be updated. endif::VK_NV_shading_rate_image[] [[primsrast-sampleshading]] == Sample Shading Sample shading can: be used to specify a minimum number of unique samples to process for each fragment. If sample shading is enabled an implementation must: provide a minimum of [eq]#max({lceil} pname:minSampleShadingFactor {times} pname:totalSamples {rceil}, 1)# unique associated data for each fragment, where pname:minSampleShadingFactor is the minimum fraction of sample shading. ifdef::VK_AMD_mixed_attachment_samples[] If the `VK_AMD_mixed_attachment_samples` extension is enabled and the subpass uses color attachments, pname:totalSamples is the number of samples of the color attachments. Otherwise, endif::VK_AMD_mixed_attachment_samples[] pname:totalSamples is the value of slink:VkPipelineMultisampleStateCreateInfo::pname:rasterizationSamples specified at pipeline creation time. These are associated with the samples in an implementation-dependent manner. When pname:minSampleShadingFactor is `1.0`, a separate set of associated data are evaluated for each sample, and each set of values is evaluated at the sample location. Sample shading is enabled for a graphics pipeline: * If the interface of the fragment shader entry point of the graphics pipeline includes an input variable decorated with code:SampleId or code:SamplePosition. In this case pname:minSampleShadingFactor takes the value `1.0`. * Else if the pname:sampleShadingEnable member of the slink:VkPipelineMultisampleStateCreateInfo structure specified when creating the graphics pipeline is set to ename:VK_TRUE. In this case pname:minSampleShadingFactor takes the value of slink:VkPipelineMultisampleStateCreateInfo::pname:minSampleShading. Otherwise, sample shading is considered disabled. ifdef::VK_NV_fragment_shader_barycentric[] [[primsrast-barycentric]] == Barycentric Interpolation When the pname:fragmentShaderBarycentric feature is enabled, the code:PerVertexNV <> can: be used with fragment shader inputs to indicate that the decorated inputs do not have associated data in the fragment. Such inputs can: only be accessed in a fragment shader using an array index whose value (0, 1, or 2) identifies one of the vertices of the primitive that produced the fragment. ifndef::VK_NV_mesh_shader[] When <> and <> endif::VK_NV_mesh_shader[] ifdef::VK_NV_mesh_shader[] When <>, <>, and <> endif::VK_NV_mesh_shader[] are not active, fragment shader inputs decorated with code:PerVertexNV will take values from one of the vertices of the primitive that produced the fragment, identified by the extra index provided in SPIR-V code accessing the input. If the _n_ vertices passed to a draw call are numbered 0 through _n_-1, and the point, line, and triangle primitives produced by the draw call are numbered with consecutive integers beginning with zero, the following table indicates the original vertex numbers used for index values of 0, 1, and 2. If an input decorated with code:PerVertexNV is accessed with any other vertex index value, the value obtained is undefined. [[primsrast-barycentric-order-table]] [options="header"] |====== | Primitive Topology | Vertex 0 | Vertex 1 | Vertex 2 | ename:VK_PRIMITIVE_TOPOLOGY_POINT_LIST | i | - | - | ename:VK_PRIMITIVE_TOPOLOGY_LINE_LIST | 2i | 2i+1 | - | ename:VK_PRIMITIVE_TOPOLOGY_LINE_STRIP | i | i+1 | - | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST | 3i | 3i+1 | 3i+2 | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP (even) | i | i+1 | i+2 | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP (odd) | i | i+2 | i+1 | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_FAN | i+1 | i+2 | 0 | ename:VK_PRIMITIVE_TOPOLOGY_LINE_LIST_WITH_ADJACENCY | 4i+1 | 4i+2 | - | ename:VK_PRIMITIVE_TOPOLOGY_LINE_STRIP_WITH_ADJACENCY | i+1 | i+2 | - | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST_WITH_ADJACENCY | 6i | 6i+2 | 6i+4 | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP_WITH_ADJACENCY (even) | 2i | 2i+2 | 2i+4 | ename:VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP_WITH_ADJACENCY (odd) | 2i | 2i+4 | 2i+2 |====== When geometry ifdef::VK_NV_mesh_shader[] or mesh endif::VK_NV_mesh_shader[] shading is active, primitives processed by fragment shaders are assembled from the vertices emitted by the geometry ifdef::VK_NV_mesh_shader[] or mesh endif::VK_NV_mesh_shader[] shader. In this case, the vertices used for fragment shader inputs decorated with code:PerVertexNV are derived by treating the primitives produced by the shader as though they were specified by a draw call and consulting <>. When using tessellation without geometry shading, the tessellator produces primitives in an implementation-dependent manner. While there is no defined vertex ordering for inputs decorated with code:PerVertexNV, the vertex ordering used in this case will be consistent with the ordering used to derive the values of inputs decorated with code::BaryCoordNV or code::BaryCoordNoPerspNV. Fragment shader inputs decorated with code:BaryCoordNV or code:BaryCoordNoPerspNV hold three-component vectors with barycentric weights that indicate the location of the fragment relative to the screen-space locations of vertices of its primitive. For point primitives, such variables are always assigned the value (1,0,0). For <> primitives, the built-ins are obtained by interpolating an attribute whose values for the vertices numbered 0 and 1 are (1,0,0) and (0,1,0), respectively. For <> primitives, the built-ins are obtained by interpolating an attribute whose values for the vertices numbered 0, 1, and 2 are (1,0,0), (0,1,0), and (0,0,1), respectively. For code:BaryCoordNV, the values are obtained using perspective interpolation. For code:BaryCoordNoPerspNV, the values are obtained using linear interpolation. endif::VK_NV_fragment_shader_barycentric[] [[primsrast-points]] == Points A point is drawn by generating a set of fragments in the shape of a square centered around the vertex of the point. Each vertex has an associated point size that controls the width/height of that square. The point size is taken from the (potentially clipped) shader built-in code:PointSize written by: * the geometry shader, if active; * the tessellation evaluation shader, if active and no geometry shader is active; * the vertex shader, otherwise and clamped to the implementation-dependent point size range [eq]#[pname:pointSizeRange[0],pname:pointSizeRange[1]]#. The value written to code:PointSize must: be greater than zero. Not all point sizes need be supported, but the size 1.0 must: be supported. The range of supported sizes and the size of evenly-spaced gradations within that range are implementation-dependent. The range and gradations are obtained from the pname:pointSizeRange and pname:pointSizeGranularity members of slink:VkPhysicalDeviceLimits. If, for instance, the size range is from 0.1 to 2.0 and the gradation size is 0.1, then the size 0.1, 0.2, ..., 1.9, 2.0 are supported. Additional point sizes may: also be supported. There is no requirement that these sizes be equally spaced. If an unsupported size is requested, the nearest supported size is used instead. ifdef::VK_EXT_fragment_density_map[] Further, if the render pass has a fragment density map attachment, point size may: be rounded by the implementation to a multiple of the fragment's width or height. endif::VK_EXT_fragment_density_map[] [[primsrast-points-basic]] === Basic Point Rasterization Point rasterization produces a fragment for each fragment area group of framebuffer pixels with one or more sample points that intersect a region centered at the point's [eq]#(x~f~,y~f~)#. This region is a square with side equal to the current point size. Coverage bits that correspond to sample points that intersect the region are 1, other coverage bits are 0. All fragments produced in rasterizing a point are assigned the same associated data, which are those of the vertex corresponding to the point. However, the fragment shader built-in code:PointCoord contains point sprite texture coordinates. The [eq]#s# and [eq]#t# point sprite texture coordinates vary from zero to one across the point horizontally left-to-right and top-to-bottom, respectively. The following formulas are used to evaluate [eq]#s# and [eq]#t#: [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ s = {1 \over 2} + { \left( x_p - x_f \right) \over \text{size} } ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ t = {1 \over 2} + { \left( y_p - y_f \right) \over \text{size} } ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where size is the point's size; [eq]#(x~p~,y~p~)# is the location at which the point sprite coordinates are evaluated - this may: be the framebuffer coordinates of the fragment center, or the location of a sample; and [eq]#(x~f~,y~f~)# is the exact, unrounded framebuffer coordinate of the vertex for the point. [[primsrast-lines]] == Line Segments A line is drawn by generating a set of fragments overlapping a rectangle centered on the line segment. Each line segment has an associated width that controls the width of that rectangle. [open,refpage='vkCmdSetLineWidth',desc='Set the dynamic line width state',type='protos'] -- The line width is specified by the slink:VkPipelineRasterizationStateCreateInfo::pname:lineWidth property of the currently active pipeline, if the pipeline was not created with ename:VK_DYNAMIC_STATE_LINE_WIDTH enabled. Otherwise, the line width is set by calling fname:vkCmdSetLineWidth: include::../api/protos/vkCmdSetLineWidth.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:lineWidth is the width of rasterized line segments. .Valid Usage **** * [[VUID-vkCmdSetLineWidth-None-00787]] The bound graphics pipeline must: have been created with the ename:VK_DYNAMIC_STATE_LINE_WIDTH dynamic state enabled * [[VUID-vkCmdSetLineWidth-lineWidth-00788]] If the <> feature is not enabled, pname:lineWidth must: be `1.0` **** include::../validity/protos/vkCmdSetLineWidth.txt[] -- Not all line widths need be supported for line segment rasterization, but width 1.0 antialiased segments must: be provided. The range and gradations are obtained from the pname:lineWidthRange and pname:lineWidthGranularity members of slink:VkPhysicalDeviceLimits. If, for instance, the size range is from 0.1 to 2.0 and the gradation size is 0.1, then the size 0.1, 0.2, ..., 1.9, 2.0 are supported. Additional line widths may: also be supported. There is no requirement that these widths be equally spaced. If an unsupported width is requested, the nearest supported width is used instead. ifdef::VK_EXT_fragment_density_map[] Further, if the render pass has a fragment density map attachment, line width may: be rounded by the implementation to a multiple of the fragment's width or height. endif::VK_EXT_fragment_density_map[] [[primsrast-lines-basic]] === Basic Line Segment Rasterization Rasterized line segments produce fragments which intersect a rectangle centered on the line segment. Two of the edges are parallel to the specified line segment; each is at a distance of one-half the current width from that segment in directions perpendicular to the direction of the line. The other two edges pass through the line endpoints and are perpendicular to the direction of the specified line segment. Coverage bits that correspond to sample points that intersect the rectangle are 1, other coverage bits are 0. Next we specify how the data associated with each rasterized fragment are obtained. Let [eq]#**p**~r~ = (x~d~, y~d~)# be the framebuffer coordinates at which associated data are evaluated. This may: be the center of a fragment or the location of a sample within the fragment. When pname:rasterizationSamples is ename:VK_SAMPLE_COUNT_1_BIT, the fragment center must: be used. Let [eq]#**p**~a~ = (x~a~, y~a~)# and [eq]#**p**~b~ = (x~b~,y~b~)# be initial and final endpoints of the line segment, respectively. Set // Equation {linet:eq} [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ t = {{( \mathbf{p}_r - \mathbf{p}_a ) \cdot ( \mathbf{p}_b - \mathbf{p}_a )} \over {\| \mathbf{p}_b - \mathbf{p}_a \|^2 }} ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ (Note that [eq]#t = 0# at [eq]#**p**~a~# and [eq]#t = 1# at [eq]#**p**~b~#. Also note that this calculation projects the vector from [eq]#**p**~a~# to [eq]#**p**~r~# onto the line, and thus computes the normalized distance of the fragment along the line.) [[line_perspective_interpolation]] The value of an associated datum [eq]#f# for the fragment, whether it be a shader output or the clip [eq]#w# coordinate, must: be determined using _perspective interpolation_: [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ f = {{ (1-t) {f_a / w_a} + t { f_b / w_b} } \over {(1-t) / w_a + t / w_b }} ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where [eq]#f~a~# and [eq]#f~b~# are the data associated with the starting and ending endpoints of the segment, respectively; [eq]#w~a~# and [eq]#w~b~# are the clip [eq]#w# coordinates of the starting and ending endpoints of the segments, respectively. [[line_linear_interpolation]] Depth values for lines must: be determined using _linear interpolation_: :: [eq]#z = (1 - t) z~a~ {plus} t z~b~# where [eq]#z~a~# and [eq]#z~b~# are the depth values of the starting and ending endpoints of the segment, respectively. The code:NoPerspective and code:Flat <> can: be used with fragment shader inputs to declare how they are interpolated. When neither decoration is applied, <> is performed as described above. When the code:NoPerspective decoration is used, <> is performed in the same fashion as for depth values, as described above. When the code:Flat decoration is used, no interpolation is performed, and outputs are taken from the corresponding input value of the <> corresponding to that primitive. ifdef::VK_NV_fragment_shader_barycentric[] When the pname:fragmentShaderBarycentric feature is enabled, the code:PerVertexNV <> can: also be used with fragment shader inputs which indicate that the decorated inputs are not interpolated and can: only be accessed using an extra array dimension, where the extra index identifies one of the vertices of the primitive that produced the fragment. endif::VK_NV_fragment_shader_barycentric[] The above description documents the preferred method of line rasterization, and must: be used when the implementation advertises the pname:strictLines limit in slink:VkPhysicalDeviceLimits as ename:VK_TRUE. When pname:strictLines is ename:VK_FALSE, the edges of the lines are generated as a parallelogram surrounding the original line. The major axis is chosen by noting the axis in which there is the greatest distance between the line start and end points. If the difference is equal in both directions then the X axis is chosen as the major axis. Edges 2 and 3 are aligned to the minor axis and are centered on the endpoints of the line as in <>, and each is pname:lineWidth long. Edges 0 and 1 are parallel to the line and connect the endpoints of edges 2 and 3. Coverage bits that correspond to sample points that intersect the parallelogram are 1, other coverage bits are 0. Samples that fall exactly on the edge of the parallelogram follow the polygon rasterization rules. Interpolation occurs as if the parallelogram was decomposed into two triangles where each pair of vertices at each end of the line has identical attributes. [[fig-non-strict-lines]] image::images/non_strict_lines.svg[align="center",title="Non strict lines",opts="{imageopts}"] [[primsrast-polygons]] == Polygons A polygon results from the decomposition of a triangle strip, triangle fan or a series of independent triangles. Like points and line segments, polygon rasterization is controlled by several variables in the slink:VkPipelineRasterizationStateCreateInfo structure. [[primsrast-polygons-basic]] === Basic Polygon Rasterization [open,refpage='VkFrontFace',desc='Interpret polygon front-facing orientation',type='enums'] -- The first step of polygon rasterization is to determine whether the triangle is _back-facing_ or _front-facing_. This determination is made based on the sign of the (clipped or unclipped) polygon's area computed in framebuffer coordinates. One way to compute this area is: [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ a = -{1 \over 2}\sum_{i=0}^{n-1} x_f^i y_f^{i \oplus 1} - x_f^{i \oplus 1} y_f^i ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where latexmath:[x_f^i] and latexmath:[y_f^i] are the [eq]#x# and [eq]#y# framebuffer coordinates of the [eq]##i##th vertex of the [eq]#n#-vertex polygon (vertices are numbered starting at zero for the purposes of this computation) and [eq]#i {oplus} 1# is [eq]#(i {plus} 1) mod n#. The interpretation of the sign of [eq]#a# is determined by the slink:VkPipelineRasterizationStateCreateInfo::pname:frontFace property of the currently active pipeline. Possible values are: include::../api/enums/VkFrontFace.txt[] * ename:VK_FRONT_FACE_COUNTER_CLOCKWISE specifies that a triangle with positive area is considered front-facing. * ename:VK_FRONT_FACE_CLOCKWISE specifies that a triangle with negative area is considered front-facing. Any triangle which is not front-facing is back-facing, including zero-area triangles. -- [open,refpage='VkCullModeFlagBits',desc='Bitmask controlling triangle culling',type='enums'] -- Once the orientation of triangles is determined, they are culled according to the slink:VkPipelineRasterizationStateCreateInfo::pname:cullMode property of the currently active pipeline. Possible values are: include::../api/enums/VkCullModeFlagBits.txt[] * ename:VK_CULL_MODE_NONE specifies that no triangles are discarded * ename:VK_CULL_MODE_FRONT_BIT specifies that front-facing triangles are discarded * ename:VK_CULL_MODE_BACK_BIT specifies that back-facing triangles are discarded * ename:VK_CULL_MODE_FRONT_AND_BACK specifies that all triangles are discarded. Following culling, fragments are produced for any triangles which have not been discarded. -- [open,refpage='VkCullModeFlags',desc='Bitmask of VkCullModeFlagBits',type='flags'] -- include::../api/flags/VkCullModeFlags.txt[] tname:VkCullModeFlags is a bitmask type for setting a mask of zero or more elink:VkCullModeFlagBits. -- The rule for determining which fragments are produced by polygon rasterization is called _point sampling_. The two-dimensional projection obtained by taking the x and y framebuffer coordinates of the polygon's vertices is formed. Fragments are produced for any fragment area groups of pixels for which any sample points lie inside of this polygon. Coverage bits that correspond to sample points that satisfy the point sampling criteria are 1, other coverage bits are 0. Special treatment is given to a sample whose sample location lies on a polygon edge. In such a case, if two polygons lie on either side of a common edge (with identical endpoints) on which a sample point lies, then exactly one of the polygons must: result in a covered sample for that fragment during rasterization. As for the data associated with each fragment produced by rasterizing a polygon, we begin by specifying how these values are produced for fragments in a triangle. Define _barycentric coordinates_ for a triangle. Barycentric coordinates are a set of three numbers, [eq]#a#, [eq]#b#, and [eq]#c#, each in the range [eq]#[0,1]#, with [eq]#a {plus} b {plus} c = 1#. These coordinates uniquely specify any point [eq]#p# within the triangle or on the triangle's boundary as :: [eq]#p = a p~a~ {plus} b p~b~ {plus} c p~c~# where [eq]#p~a~#, [eq]#p~b~#, and [eq]#p~c~# are the vertices of the triangle. [eq]#a#, [eq]#b#, and [eq]#c# are determined by: [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ a = {{\mathrm{A}(p p_b p_c)} \over {\mathrm{A}(p_a p_b p_c)}}, \quad b = {{\mathrm{A}(p p_a p_c)} \over {\mathrm{A}(p_a p_b p_c)}}, \quad c = {{\mathrm{A}(p p_a p_b)} \over {\mathrm{A}(p_a p_b p_c)}}, ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where [eq]#A(lmn)# denotes the area in framebuffer coordinates of the triangle with vertices [eq]#l#, [eq]#m#, and [eq]#n#. Denote an associated datum at [eq]#p~a~#, [eq]#p~b~#, or [eq]#p~c~# as [eq]#f~a~#, [eq]#f~b~#, or [eq]#f~c~#, respectively. [[triangle_perspective_interpolation]] The value of an associated datum [eq]#f# for a fragment produced by rasterizing a triangle, whether it be a shader output or the clip [eq]#w# coordinate, must: be determined using perspective interpolation: [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ f = { a {f_a / w_a} + b {f_b / w_b} + c {f_c / w_c} } \over { {a / w_a} + {b / w_b} + {c / w_c} } ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where [eq]#w~a~#, [eq]#w~b~#, and [eq]#w~c~# are the clip [eq]#w# coordinates of [eq]#p~a~#, [eq]#p~b~#, and [eq]#p~c~#, respectively. [eq]#a#, [eq]#b#, and [eq]#c# are the barycentric coordinates of the location at which the data are produced - this must: be the location of the fragment center or the location of a sample. When pname:rasterizationSamples is ename:VK_SAMPLE_COUNT_1_BIT, the fragment center must: be used. [[triangle_linear_interpolation]] Depth values for triangles must: be determined using linear interpolation: :: [eq]#z = a z~a~ {plus} b z~b~ {plus} c z~c~# where [eq]#z~a~#, [eq]#z~b~#, and [eq]#z~c~# are the depth values of [eq]#p~a~#, [eq]#p~b~#, and [eq]#p~c~#, respectively. The code:NoPerspective and code:Flat <> can: be used with fragment shader inputs to declare how they are interpolated. When neither decoration is applied, <> is performed as described above. When the code:NoPerspective decoration is used, <> is performed in the same fashion as for depth values, as described above. When the code:Flat decoration is used, no interpolation is performed, and outputs are taken from the corresponding input value of the <> corresponding to that primitive. ifdef::VK_AMD_shader_explicit_vertex_parameter[] When the `<>` device extension is enabled the code:CustomInterpAMD <> can: also be used with fragment shader inputs which indicate that the decorated inputs can: only be accessed by the extended instruction code:InterpolateAtVertexAMD and allows accessing the value of the inputs for individual vertices of the primitive. endif::VK_AMD_shader_explicit_vertex_parameter[] ifdef::VK_NV_fragment_shader_barycentric[] When the pname:fragmentShaderBarycentric feature is enabled, the code:PerVertexNV <> can: also be used with fragment shader inputs which indicate that the decorated inputs are not interpolated and can: only be accessed using an extra array dimension, where the extra index identifies one of the vertices of the primitive that produced the fragment. endif::VK_NV_fragment_shader_barycentric[] For a polygon with more than three edges, such as are produced by clipping a triangle, a convex combination of the values of the datum at the polygon's vertices must: be used to obtain the value assigned to each fragment produced by the rasterization algorithm. That is, it must: be the case that at every fragment [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ f = \sum_{i=1}^{n} a_i f_i ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where [eq]#n# is the number of vertices in the polygon and [eq]#f~i~# is the value of [eq]#f# at vertex [eq]#i#. For each [eq]#i#, [eq]#0 {leq} a~i~ {leq} 1# and latexmath:[\sum_{i=1}^{n}a_i = 1]. The values of [eq]#a~i~# may: differ from fragment to fragment, but at vertex [eq]#i#, [eq]#a~i~ = 1# and [eq]#a~j~ = 0# for [eq]#j {neq} i#. [NOTE] .Note ==== One algorithm that achieves the required behavior is to triangulate a polygon (without adding any vertices) and then treat each triangle individually as already discussed. A scan-line rasterizer that linearly interpolates data along each edge and then linearly interpolates data across each horizontal span from edge to edge also satisfies the restrictions (in this case, the numerator and denominator of equation <> are iterated independently and a division performed for each fragment). ==== [[primsrast-polygonmode]] === Polygon Mode [open,refpage='VkPolygonMode',desc='Control polygon rasterization mode',type='enums'] -- Possible values of the slink:VkPipelineRasterizationStateCreateInfo::pname:polygonMode property of the currently active pipeline, specifying the method of rasterization for polygons, are: include::../api/enums/VkPolygonMode.txt[] * ename:VK_POLYGON_MODE_POINT specifies that polygon vertices are drawn as points. * ename:VK_POLYGON_MODE_LINE specifies that polygon edges are drawn as line segments. * ename:VK_POLYGON_MODE_FILL specifies that polygons are rendered using the polygon rasterization rules in this section. ifdef::VK_NV_fill_rectangle[] * ename:VK_POLYGON_MODE_FILL_RECTANGLE_NV specifies that polygons are rendered using polygon rasterization rules, modified to consider a sample within the primitive if the sample location is inside the axis-aligned bounding box of the triangle after projection. Note that the barycentric weights used in attribute interpolation can: extend outside the range [eq]#[0,1]# when these primitives are shaded. Special treatment is given to a sample position on the boundary edge of the bounding box. In such a case, if two rectangles lie on either side of a common edge (with identical endpoints) on which a sample position lies, then exactly one of the triangles must: produce a fragment that covers that sample during rasterization. + Polygons rendered in ename:VK_POLYGON_MODE_FILL_RECTANGLE_NV mode may: be clipped by the frustum or by user clip planes. If clipping is applied, the triangle is culled rather than clipped. + Area calculation and facingness are determined for ename:VK_POLYGON_MODE_FILL_RECTANGLE_NV mode using the triangle's vertices. endif::VK_NV_fill_rectangle[] These modes affect only the final rasterization of polygons: in particular, a polygon's vertices are shaded and the polygon is clipped and possibly culled before these modes are applied. -- [[primsrast-depthbias]] === Depth Bias [open,refpage='vkCmdSetDepthBias',desc='Set the depth bias dynamic state',type='protos'] -- The depth values of all fragments generated by the rasterization of a polygon can: be offset by a single value that is computed for that polygon. This behavior is controlled by the pname:depthBiasEnable, pname:depthBiasConstantFactor, pname:depthBiasClamp, and pname:depthBiasSlopeFactor members of slink:VkPipelineRasterizationStateCreateInfo, or by the corresponding parameters to the fname:vkCmdSetDepthBias command if depth bias state is dynamic. include::../api/protos/vkCmdSetDepthBias.txt[] * pname:commandBuffer is the command buffer into which the command will be recorded. * pname:depthBiasConstantFactor is a scalar factor controlling the constant depth value added to each fragment. * pname:depthBiasClamp is the maximum (or minimum) depth bias of a fragment. * pname:depthBiasSlopeFactor is a scalar factor applied to a fragment's slope in depth bias calculations. If pname:depthBiasEnable is ename:VK_FALSE, no depth bias is applied and the fragment's depth values are unchanged. pname:depthBiasSlopeFactor scales the maximum depth slope of the polygon, and pname:depthBiasConstantFactor scales an implementation-dependent constant that relates to the usable resolution of the depth buffer. The resulting values are summed to produce the depth bias value which is then clamped to a minimum or maximum value specified by pname:depthBiasClamp. pname:depthBiasSlopeFactor, pname:depthBiasConstantFactor, and pname:depthBiasClamp can: each be positive, negative, or zero. The maximum depth slope [eq]#m# of a triangle is [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ m = \sqrt{ \left({{\partial z_f} \over {\partial x_f}}\right)^2 + \left({{\partial z_f} \over {\partial y_f}}\right)^2} ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ where [eq]#(x~f~, y~f~, z~f~)# is a point on the triangle. [eq]#m# may: be approximated as [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ m = \max\left( \left| { {\partial z_f} \over {\partial x_f} } \right|, \left| { {\partial z_f} \over {\partial y_f} } \right| \right). ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ The minimum resolvable difference [eq]#r# is an implementation-dependent parameter that depends on the depth buffer representation. It is the smallest difference in framebuffer coordinate [eq]#z# values that is guaranteed to remain distinct throughout polygon rasterization and in the depth buffer. All pairs of fragments generated by the rasterization of two polygons with otherwise identical vertices, but [eq]#pname:z~f~# values that differ by [eq]#r#, will have distinct depth values. For fixed-point depth buffer representations, [eq]#r# is constant throughout the range of the entire depth buffer. For floating-point depth buffers, there is no single minimum resolvable difference. In this case, the minimum resolvable difference for a given polygon is dependent on the maximum exponent, [eq]#e#, in the range of [eq]#z# values spanned by the primitive. If [eq]#n# is the number of bits in the floating-point mantissa, the minimum resolvable difference, [eq]#r#, for the given primitive is defined as :: [eq]#r = 2^e-n^# ifdef::VK_NV_fill_rectangle[] If a triangle is rasterized using the ename:VK_POLYGON_MODE_FILL_RECTANGLE_NV polygon mode, then this minimum resolvable difference may: not be resolvable for samples outside of the triangle, where the depth is extrapolated. endif::VK_NV_fill_rectangle[] If no depth buffer is present, [eq]#r# is undefined:. The bias value [eq]#o# for a polygon is [latexmath] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ \begin{aligned} o &= \mathrm{dbclamp}( m \times \mathtt{depthBiasSlopeFactor} + r \times \mathtt{depthBiasConstantFactor} ) \\ \text{where} &\quad \mathrm{dbclamp}(x) = \begin{cases} x & \mathtt{depthBiasClamp} = 0 \ \text{or}\ \texttt{NaN} \\ \min(x, \mathtt{depthBiasClamp}) & \mathtt{depthBiasClamp} > 0 \\ \max(x, \mathtt{depthBiasClamp}) & \mathtt{depthBiasClamp} < 0 \\ \end{cases} \end{aligned} ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ [eq]#m# is computed as described above. If the depth buffer uses a fixed-point representation, [eq]#m# is a function of depth values in the range [eq]#[0,1]#, and [eq]#o# is applied to depth values in the same range. For fixed-point depth buffers, fragment depth values are always limited to the range [eq]#[0,1]# by clamping after depth bias addition is performed. ifdef::VK_EXT_depth_range_unrestricted[] Unless the `<>` extension is enabled, fragment depth values are clamped even when the depth buffer uses a floating-point representation. endif::VK_EXT_depth_range_unrestricted[] ifndef::VK_EXT_depth_range_unrestricted[] Fragment depth values are clamped even when the depth buffer uses a floating-point representation. endif::VK_EXT_depth_range_unrestricted[] .Valid Usage **** * [[VUID-vkCmdSetDepthBias-None-00789]] The bound graphics pipeline must: have been created with the ename:VK_DYNAMIC_STATE_DEPTH_BIAS dynamic state enabled * [[VUID-vkCmdSetDepthBias-depthBiasClamp-00790]] If the <> feature is not enabled, pname:depthBiasClamp must: be `0.0` **** include::../validity/protos/vkCmdSetDepthBias.txt[] -- ifdef::VK_EXT_conservative_rasterization[] [[primsrast-conservativeraster]] === Conservative Rasterization [open,refpage='VkPipelineRasterizationConservativeStateCreateInfoEXT',desc='Structure specifying conservative raster state',type='structs'] -- Polygon rasterization can: be made conservative by setting pname:conservativeRasterizationMode to ename:VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT or ename:VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT in sname:VkPipelineRasterizationConservativeStateCreateInfoEXT. The sname:VkPipelineRasterizationConservativeStateCreateInfoEXT state is set by adding an instance of this structure to the pname:pNext chain of an instance of the sname:VkPipelineRasterizationStateCreateInfo structure when creating the graphics pipeline. Enabling these modes also affects line and point rasterization if the implementation sets sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:conservativePointAndLineRasterization to ename:VK_TRUE. sname:VkPipelineRasterizationConservativeStateCreateInfoEXT is defined as: include::../api/structs/VkPipelineRasterizationConservativeStateCreateInfoEXT.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:conservativeRasterizationMode is the conservative rasterization mode to use. * pname:extraPrimitiveOverestimationSize is the extra size in pixels to increase the generating primitive during conservative rasterization at each of its edges in `X` and `Y` equally in screen space beyond the base overestimation specified in sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:primitiveOverestimationSize. .Valid Usage **** * [[VUID-VkPipelineRasterizationConservativeStateCreateInfoEXT-extraPrimitiveOverestimationSize-01769]] pname:extraPrimitiveOverestimationSize must: be in the range of `0.0` to sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:maxExtraPrimitiveOverestimationSize inclusive **** include::../validity/structs/VkPipelineRasterizationConservativeStateCreateInfoEXT.txt[] -- [open,refpage='VkPipelineRasterizationConservativeStateCreateFlagsEXT',desc='Reserved for future use',type='flags'] -- include::../api/flags/VkPipelineRasterizationConservativeStateCreateFlagsEXT.txt[] tname:VkPipelineRasterizationConservativeStateCreateFlagsEXT is a bitmask type for setting a mask, but is currently reserved for future use. -- [open,refpage='VkConservativeRasterizationModeEXT',desc='Specify the conservative rasterization mode',type='enums'] -- Possible values of slink:VkPipelineRasterizationConservativeStateCreateInfoEXT::pname:conservativeRasterizationMode, specifying the conservative rasterization mode are: include::../api/enums/VkConservativeRasterizationModeEXT.txt[] * ename:VK_CONSERVATIVE_RASTERIZATION_MODE_DISABLED_EXT specifies that conservative rasterization is disabled and rasterization proceeds as normal. * ename:VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT specifies that conservative rasterization is enabled in overestimation mode. * ename:VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT specifies that conservative rasterization is enabled in underestimation mode. -- When overestimate conservative rasterization is enabled, rather than evaluating coverage at individual sample locations, a determination is made of whether any portion of the pixel (including its edges and corners) is covered by the primitive. If any portion of the pixel is covered, then all bits of the coverage sample mask for the fragment corresponding to that pixel are enabled. ifdef::VK_EXT_fragment_density_map[] If the render pass has a fragment density map attachment and any bit of the coverage sample mask for the fragment is enabled, then all bits of the coverage sample mask for the fragment are enabled. endif::VK_EXT_fragment_density_map[] ifdef::VK_EXT_post_depth_coverage[] If the implementation supports sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:conservativeRasterizationPostDepthCoverage and the <> execution mode is specified the code:SampleMask built-in input variable will reflect the coverage after the early per-fragment depth and stencil tests are applied. endif::VK_EXT_post_depth_coverage[] For the purposes of evaluating which pixels are covered by the primitive, implementations can: increase the size of the primitive by up to sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:primitiveOverestimationSize pixels at each of the primitive edges. This may: increase the number of fragments generated by this primitive and represents an overestimation of the pixel coverage. This overestimation size can be increased further by setting the pname:extraPrimitiveOverestimationSize value above `0.0` in steps of sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:extraPrimitiveOverestimationSizeGranularity up to and including sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:extraPrimitiveOverestimationSize. This will: further increase the number of fragments generated by this primitive. The actual precision of the overestimation size used for conservative rasterization may: vary between implementations and produce results that only approximate the pname:primitiveOverestimationSize and pname:extraPrimitiveOverestimationSizeGranularity properties. ifdef::VK_EXT_fragment_density_map[] Implementations may: especially vary these approximations when the render pass has a fragment density map and the fragment area covers multiple pixels. endif::VK_EXT_fragment_density_map[] For triangles if ename:VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT is enabled, fragments will be generated if the primitive area covers any portion of any pixel inside the fragment area, including their edges or corners. The tie-breaking rule described in <> does not apply during conservative rasterization and coverage is set for all fragments generated from shared edges of polygons. Degenerate triangles that evaluate to zero area after rasterization, even for pixels that contain a vertex or edge of the zero-area polygon, will be culled if sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:degenerateTrianglesRasterized is ename:VK_FALSE or will generate fragments if pname:degenerateTrianglesRasterized is ename:VK_TRUE. The fragment input values for these degenerate triangles take their attribute and depth values from the provoking vertex. Degenerate triangles are considered backfacing and the application can: enable backface culling if desired. Triangles that are zero area before rasterization may: be culled regardless. For lines if ename:VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT is enabled, and the implementation sets sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:conservativePointAndLineRasterization to ename:VK_TRUE, fragments will be generated if the line covers any portion of any pixel inside the fragment area, including their edges or corners. Degenerate lines that evaluate to zero length after rasterization will be culled if sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:degenerateLinesRasterized is ename:VK_FALSE or will generate fragments if pname:degenerateLinesRasterized is ename:VK_TRUE. The fragments input values for these degenerate lines take their attribute and depth values from the provoking vertex. Lines that are zero length before rasterization may: be culled regardless. For points if ename:VK_CONSERVATIVE_RASTERIZATION_MODE_OVERESTIMATE_EXT is enabled, and the implementation sets sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:conservativePointAndLineRasterization to ename:VK_TRUE, fragments will be generated if the point square covers any portion of any pixel inside the fragment area, including their edges or corners. When underestimate conservative rasterization is enabled, rather than evaluating coverage at individual sample locations, a determination is made of whether all of the pixel (including its edges and corners) is covered by the primitive. If the entire pixel is covered, then a fragment is generated with all bits of its coverage sample mask corresponding to the pixel enabled, otherwise the pixel is not considered covered even if some portion of the pixel is covered. The fragment is discarded if no pixels inside the fragment area are considered covered. ifdef::VK_EXT_fragment_density_map[] If the render pass has a fragment density map attachment and any pixel inside the fragment area is not considered covered, then the fragment is discarded even if some pixels are considered covered. endif::VK_EXT_fragment_density_map[] ifdef::VK_EXT_post_depth_coverage[] If the implementation supports sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:conservativeRasterizationPostDepthCoverage and the <> execution mode is specified the code:SampleMask built-in input variable will reflect the coverage after the early per-fragment depth and stencil tests are applied. endif::VK_EXT_post_depth_coverage[] For triangles, if ename:VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT is enabled, fragments will only be generated if any pixel inside the fragment area is fully covered by the generating primitive, including its edges and corners. For lines, if ename:VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT is enabled, fragments will be generated if any pixel inside the fragment area, including its edges and corners, are entirely covered by the line. For points, if ename:VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT is enabled, fragments will only be generated if the point square covers the entirety of any pixel square inside the fragment area, including its edges or corners. ifdef::VK_EXT_fragment_density_map[] If the render pass has a fragment density map and ename:VK_CONSERVATIVE_RASTERIZATION_MODE_UNDERESTIMATE_EXT is enabled, fragments will only be generated if the entirety of all pixels inside the fragment area are covered by the generating primitive, line, or point. endif::VK_EXT_fragment_density_map[] For both overestimate and underestimate conservative rasterization modes a fragment has all of its pixel squares fully covered by the generating primitive must: set code:FullyCoveredEXT to ename:VK_TRUE if the implementation enables the sname:VkPhysicalDeviceConservativeRasterizationPropertiesEXT::pname:fullyCoveredFragmentShaderInputVariable feature. ifdef::VK_NV_shading_rate_image[] When the use of a <> results in fragments covering multiple pixels, coverage for conservative rasterization is still evaluated on a per-pixel basis and may result in fragments with partial coverage. For fragment shader inputs decorated with code:FullyCoveredEXT, a fragment is considered fully covered if and only if all pixels in the fragment are fully covered by the generating primitive. endif::VK_NV_shading_rate_image[] endif::VK_EXT_conservative_rasterization[]