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Vulkan-Docs/appendices/VK_NV_mesh_shader.txt

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Change log for September 19, 2018 Vulkan 1.1.85 spec update: * Update release number to 85. Public Issues: * Add self-dependency ename:VK_DEPENDENCY_BY_REGION_BIT valid usage statements for slink:VkSubpassDependency(public pull request 778). * Apply fix from pull request 742 to slink:VkSubpassDependency and slink:VkSubpassDependency2 (public pull request 779). * Specify the units of slink:VkBufferImageCopy::pname:bufferRowLength and pname:bufferImageHeight as texels (public pull request 781). * Better specify promoted parameter mapping in the `<<VK_KHR_create_renderpass2>>` appendix (public pull request 782). Internal Issues: * Only include the <<fundamentals-validusage-versions, Valid Usage for Newer Core Versions>> section in Vulkan 1.1 or later (internal issue 1381). Other Issues: * Clean up redundant valid usage language for the `VK_ANDROID_external_memory_android_hardware_buffer` extension interaction with slink:VkImageCreateInfo. * Fix error in a flag name within valid usage statements for slink:VkMemoryAllocateInfo. * Clarify that memory types are not totally ordered in slink:VkPhysicalDeviceMemoryProperties. * For slink:VkWriteDescriptorSetInlineUniformBlockEXT, set structextends="VkWriteDescriptorSet" in `vk.xml`, and make slink:VkDescriptorSetLayoutBindingFlagsCreateInfoEXT::pname:pBindingFlags optional. * Add documentation of 'provisional' XML attribute to registry.txt. New Extensions: * `VK_NV_compute_shader_derivatives` * `VK_NV_corner_sampled_image` * `VK_NV_fragment_shader_barycentric` * `VK_NV_mesh_shader` * `VK_NV_representative_fragment_test` * `VK_NV_scissor_exclusive` * `VK_NV_shader_image_footprint` * `VK_NV_shading_rate_image` * `VK_NVX_raytracing`
2018-09-16 01:35:16 +00:00
include::meta/VK_NV_mesh_shader.txt[]
*Last Modified Date*::
2018-07-19
*Contributors*::
- Pat Brown, NVIDIA
- Jeff Bolz, NVIDIA
- Daniel Koch, NVIDIA
- Piers Daniell, NVIDIA
- Pierre Boudier, NVIDIA
This extension provides a new mechanism allowing applications to generate
collections of geometric primitives via programmable mesh shading.
It is an alternative to the existing programmable primitive shading
pipeline, which relied on generating input primitives by a fixed function
assembler as well as fixed function vertex fetch.
There are new programmable shader types -- the task and mesh shader -- to
generate these collections to be processed by fixed-function primitive
assembly and rasterization logic.
When the task and mesh shaders are dispatched, they replace the standard
programmable vertex processing pipeline, including vertex array attribute
fetching, vertex shader processing, tessellation, and the geometry shader
processing.
This extension also adds support for the following SPIR-V extension in
Vulkan:
* SPV_NV_mesh_shader
=== New Object Types
None.
=== New Enum Constants
* Extending elink:VkStructureType:
** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_MESH_SHADER_FEATURES_NV
** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_MESH_SHADER_PROPERTIES_NV
* Extending elink:VkShaderStageFlagBits
** ename:VK_SHADER_STAGE_TASK_BIT_NV
** ename:VK_SHADER_STAGE_MESH_BIT_NV
* Extending elink:VkPipelineStageFlagBits
** ename:VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV
** ename:VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV
=== New Enums
None.
=== New Structures
* slink:VkPhysicalDeviceMeshShaderFeaturesNV
* slink:VkPhysicalDeviceMeshShaderPropertiesNV
* slink:VkDrawMeshTasksIndirectCommandNV
=== New Functions
* flink:vkCmdDrawMeshTasksNV
* flink:vkCmdDrawMeshTasksIndirectNV
* flink:vkCmdDrawMeshTasksIndirectCountNV
=== New or Modified Built-In Variables
* <<interfaces-builtin-variables-taskcount,TaskCountNV>>
* <<interfaces-builtin-variables-primitivecount,PrimitiveCountNV>>
* <<interfaces-builtin-variables-primitiveindices,PrimitiveIndicesNV>>
* <<interfaces-builtin-variables-clipdistancepv,ClipDistancePerViewNV>>
* <<interfaces-builtin-variables-culldistancepv,CullDistancePerViewNV>>
* <<interfaces-builtin-variables-layerpv,LayerPerViewNV>>
* <<interfaces-builtin-variables-meshviewcount,MeshViewCountNV>>
* <<interfaces-builtin-variables-meshviewindices,MeshViewIndicesNV>>
* (modified)code:Position
* (modified)code:PointSize
* (modified)code:ClipDistance
* (modified)code:CullDistance
* (modified)code:PrimitiveId
* (modified)code:Layer
* (modified)code:ViewportIndex
* (modified)code:WorkgroupSize
* (modified)code:WorkgroupId
* (modified)code:LocalInvocationId
* (modified)code:GlobalInvocationId
* (modified)code:LocalInvocationIndex
* (modified)code:DrawIndex
* (modified)code:ViewportMaskNV
* (modified)code:PositionPerViewNV
* (modified)code:ViewportMaskPerViewNV
=== New SPIR-V Capability
* <<spirvenv-capabilities-table-meshshading,MeshShadingNV>>
=== Issues
. How to name this extension?
+
--
RESOLVED: VK_NV_mesh_shader
Other options considered:
* VK_NV_mesh_shading
* VK_NV_programmable_mesh_shading
* VK_NV_primitive_group_shading
* VK_NV_grouped_drawing
--
. Do we need a new VkPrimitiveTopology?
+
--
RESOLVED: NO, we skip the InputAssembler stage
--
. Should we allow Instancing?
+
--
RESOLVED: NO, there is no fixed function input, other than the IDs.
However, allow offsetting with a "first" value.
--
. Should we use existing vkCmdDraw or introduce new functions?
+
--
RESOLVED: Introduce new functions.
New functions make it easier to separate from "programmable primitive
shading" chapter, less "dual use" language about existing functions having
alternative behavior.
The text around the existing "draws" is heavily based around emitting
vertices.
--
. If new functions, how to name?
+
--
RESOLVED: CmdDrawMeshTasks*
Other options considered:
* CmdDrawMeshed
* CmdDrawTasked
* CmdDrawGrouped
--
. Should VK_SHADER_STAGE_ALL_GRAPHICS be updated to include the new stages?
+
--
RESOLVED: No.
If an application were to be recompiled with headers that include additional
shader stage bits in VK_SHADER_STAGE_ALL_GRAPHICS, then the previously valid
application would no longer be valid on implementations that don't support
mesh or task shaders.
This means the change would not be backwards compatible.
It's too bad VkShaderStageFlagBits doesn't have a dedicated "all supported
graphics stages" bit like VK_PIPELINE_STAGE_ALL_GRAPHICS_BIT, which would
have avoided this problem.
--
=== Version History
* Revision 1, 2018-07-19 (Christoph Kubisch, Daniel Koch)
- Internal revisions