Vulkan-Docs/doc/specs/vulkan/chapters/samplers.txt

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// Copyright (c) 2015-2016 The Khronos Group Inc.
// Copyright notice at https://www.khronos.org/registry/speccopyright.html
[[samplers]]
= Samplers
sname:VkSampler objects encapsulate the state of an image sampler which is
used by the implementation to read image data and apply filtering and other
transformations for the shader.
To create a sampler object, call:
include::../protos/vkCreateSampler.txt[]
* pname:device is the logical device that creates the sampler.
* pname:pCreateInfo is a pointer to an instance of the
slink:VkSamplerCreateInfo structure specifying the state of the sampler
object.
* pname:pAllocator controls host memory allocation as described in the
<<memory-allocation, Memory Allocation>> chapter.
* pname:pSampler points to a sname:VkSampler handle in which the resulting
sampler object is returned.
include::../validity/protos/vkCreateSampler.txt[]
The sname:VkSamplerCreateInfo structure is defined as:
include::../structs/VkSamplerCreateInfo.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:magFilter is the magnification filter to apply to lookups, and
is of type:
+
--
include::../enums/VkFilter.txt[]
--
+
* pname:minFilter is the minification filter to apply to lookups, and is
of type elink:VkFilter.
* pname:mipmapMode is the mipmap filter to apply to lookups as described
in the <<textures-texel-filtering, Texel Filtering>> section, and is of
type:
+
--
include::../enums/VkSamplerMipmapMode.txt[]
--
+
* pname:addressModeU is the addressing mode for outside [0..1] range for U
coordinate. See elink:VkSamplerAddressMode.
* pname:addressModeV is the addressing mode for outside [0..1] range for V
coordinate. See elink:VkSamplerAddressMode.
* pname:addressModeW is the addressing mode for outside [0..1] range for W
coordinate. See elink:VkSamplerAddressMode.
* [[samplers-mipLodBias]] pname:mipLodBias is the bias to be added to
mipmap LOD calculation and bias provided by image sampling functions in
SPIR-V, as described in the <<textures-level-of-detail-operation,
Level-of-Detail Operation>> section.
* [[samplers-maxAnisotropy]] pname:anisotropyEnable is ename:VK_TRUE to
enable anisotropic filtering, as described in the
<<textures-texel-anisotropic-filtering, Texel Anisotropic Filtering>>
section, or ename:VK_FALSE otherwise.
* pname:maxAnisotropy is the anisotropy value clamp.
* pname:compareEnable is ename:VK_TRUE to enable comparison against a
reference value during lookups, or ename:VK_FALSE otherwise.
** Note: Some implementations will default to shader state if this member
does not match.
* pname:compareOp is the comparison function to apply to fetched data
before filtering as described in the <<textures-depth-compare-operation,
Depth Compare Operation>> section. See elink:VkCompareOp.
* pname:minLod and pname:maxLod are the values used to clamp the computed
level-of-detail value, as described in the
<<textures-level-of-detail-operation, Level-of-Detail Operation>>
section. pname:maxLod must: be greater than or equal to pname:minLod.
* pname:borderColor is the predefined border color to use, as described
in the <<textures-texel-replacement, Texel Replacement>>
section, and is of type:
+
--
include::../enums/VkBorderColor.txt[]
--
+
* [[samplers-unnormalizedCoordinates]] pname:unnormalizedCoordinates
controls whether to use unnormalized or normalized texel coordinates to
address texels of the image. When set to ename:VK_TRUE, the range of the
image coordinates used to lookup the texel is in the range of zero to
the image dimensions for x, y and z. When set to ename:VK_FALSE the
range of image coordinates is zero to one. When
pname:unnormalizedCoordinates is ename:VK_TRUE, samplers have the
following requirements:
** pname:minFilter and pname:magFilter must: be equal.
** pname:mipmapMode must: be ename:VK_SAMPLER_MIPMAP_MODE_NEAREST.
** pname:minLod and pname:maxLod must: be zero.
** pname:addressModeU and pname:addressModeV must: each
be either ename:VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE or
ename:VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_BORDER.
** pname:anisotropyEnable must: be ename:VK_FALSE.
** pname:compareEnable must: be ename:VK_FALSE.
* When pname:unnormalizedCoordinates is ename:VK_TRUE, images the sampler
is used with in the shader have the following requirements:
** The pname:viewType must: be either ename:VK_IMAGE_VIEW_TYPE_1D or
ename:VK_IMAGE_VIEW_TYPE_2D.
** The image view must: have a single layer and a single mip level.
* When pname:unnormalizedCoordinates is ename:VK_TRUE, image built-in
functions in the shader that use the sampler have the following
requirements:
** The functions mustnot: use projection.
** The functions mustnot: use offsets.
[NOTE]
.Mapping of OpenGL to Vulkan filter modes
==================
pname:magFilter values of ename:VK_FILTER_NEAREST and ename:VK_FILTER_LINEAR
directly correspond to code:GL_NEAREST and code:GL_LINEAR magnification
filters. pname:minFilter and pname:mipmapMode combine to correspond to the
similarly named OpenGL minification filter of
code:GL_minFilter_MIPMAP_mipmapMode (e.g. pname:minFilter of
ename:VK_FILTER_LINEAR and pname:mipmapMode of
ename:VK_SAMPLER_MIPMAP_MODE_NEAREST correspond to
code:GL_LINEAR_MIPMAP_NEAREST).
There are no Vulkan filter modes that directly correspond to OpenGL
minification filters of code:GL_LINEAR or code:GL_NEAREST, but they can: be
emulated using ename:VK_SAMPLER_MIPMAP_MODE_NEAREST, pname:minLod = 0, and
pname:maxLod = 0.25, and using pname:minFilter = ename:VK_FILTER_LINEAR or
pname:minFilter = ename:VK_FILTER_NEAREST, respectively.
Note that using a pname:maxLod of zero would cause
<<textures-texel-filtering,magnification>> to always be performed, and the
pname:magFilter to always be used. This is valid, just not an exact match
for OpenGL behavior. Clamping the maximum lod to 0.25 allows the
latexmath:[$\lambda$] value to be non-zero and minification to be performed,
while still always rounding down to the base level. If the pname:minFilter
and pname:magFilter are equal, then using a pname:maxLod of zero also works.
==================
include::../validity/structs/VkSamplerCreateInfo.txt[]
pname:addressModeU, pname:addressModeV, and pname:addressModeW must: each
have one of the following values:
include::../enums/VkSamplerAddressMode.txt[]
These values control the behavior of sampling with coordinates outside the
range [0,1] for the respective u, v, or w coordinate as defined in the
<<textures-wrapping-operation, Wrapping Operation>> section.
* ename:VK_SAMPLER_ADDRESS_MODE_REPEAT indicates that the repeat wrap mode
will be used.
* ename:VK_SAMPLER_ADDRESS_MODE_MIRRORED_REPEAT indicates that the
mirrored repeat wrap mode will be used.
* ename:VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE indicates that the clamp to
edge wrap mode will be used.
* ename:VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_BORDER indicates that the clamp
to border wrap mode will be used.
* ename:VK_SAMPLER_ADDRESS_MODE_MIRROR_CLAMP_TO_EDGE indicates that
the mirror clamp to edge wrap mode will be used. This is only valid
if the VK_KHR_mirror_clamp_to_edge extension is enabled.
The maximum number of sampler objects which can: be simultaneously created
on a device is implementation-dependent and specified by the
<<features-limits-maxSamplerAllocationCount,pname:maxSamplerAllocationCount>>
member of the sname:VkPhysicalDeviceLimits structure. If
pname:maxSamplerAllocationCount is exceeded, fname:vkCreateSampler will
return ename:VK_ERROR_TOO_MANY_OBJECTS.
Since sname:VkSampler is a non-dispatchable handle type, implementations
may: return the same handle for sampler state vectors that are identical. In
such cases, all such objects would only count once against the
pname:maxSamplerAllocationCount limit.
To destroy a sampler, call:
include::../protos/vkDestroySampler.txt[]
* pname:device is the logical device that destroys the sampler.
* pname:sampler is the sampler to destroy.
* pname:pAllocator controls host memory allocation as described in the
<<memory-allocation, Memory Allocation>> chapter.
include::../validity/protos/vkDestroySampler.txt[]