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* Update release number to 99.
Public Issues:
* Add missing pname:pMemoryHostPointerProperties description to
flink:vkGetMemoryHostPointerPropertiesEXT.txt (public pull request 896).
* Minor markup fixes (public pull request 900).
* Minor update to `khronos.css` and markup fixes (originally proposed in
public pull request 901, but done via an internal MR).
Internal Issues:
* Document restrictions on image queries for Y'CbCr formats in the
<<features-formats-requiring-sampler-ycbcr-conversion>> table as well as
for slink:sname:VkImageFormatProperties and slink:VkImageCreateInfo
(internal issue 1361).
* Correct type of the code:FragSizeEXT built-in in the
<<interfaces-builtin-variables, Built-In Variables>> section (internal
issue 1526).
* Clean up math in the <<textures, Image Operations>> chapter by
refactoring, using better naming conventions, updating diagrams to use
the correct orientation, etc. (internal merge request 2968).
* Fix minor typos for slink:VkImageCreateInfo and
slink:VkImageStencilUsageCreateInfoEXT.
* Add missing documentation for tlink:VkResolveModeFlagsKHR.
* Fix extension dependency of pname:scalarBlockLayout in the
<<features-features-requirements, Feature Requirements>> section.
* Fix indexing math for shader binding table calculations in the
<<shader-binding-table-indexing-rules, Indexing Rules>> section, and use
spelling "`any-hit`" consistently.
* Reconcile valid usage statement and text for sampled image layouts in
slink:VkWriteDescriptorSet
(https://github.com/KhronosGroup/Vulkan-ValidationLayers/issues/551).
* Make SPIR-V code:OpConvertUToPtr and code:OpConvertPtrToU operations
require a 64-bit integer for physical storage buffer pointers in the
<<spirvenv-module-validation, Validation Rules within a Module>>
section.
* Update to KaTeX 10.0.
New Extensions:
* `VK_EXT_filter_cubic`
* `VK_NV_dedicated_allocation_image_aliasing`
110 lines
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110 lines
3.9 KiB
Plaintext
// This section is included inside the Shaders chapter (shaders.txt)
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[[shaders-raytracing-shaders]]
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[[shaders-ray-generation]]
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== Ray Generation Shaders
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A ray generation shader is similar to a compute shader.
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Its main purpose is to execute ray tracing queries using code:OpTraceNV
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instructions and process the results.
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[[shaders-ray-generation-execution]]
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=== Ray Generation Shader Execution
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One ray generation shader is executed per ray tracing dispatch.
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Its location in the shader binding table (see <<shader-binding-table,Shader
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Binding Table>> for details) is passed directly into fname:vkCmdTraceRaysNV
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using the pname:raygenShaderBindingTableBuffer and
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pname:raygenShaderBindingOffset parameters.
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[[shaders-intersection]]
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== Intersection Shaders
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Intersection shaders enable the implementation of arbitrary, application
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defined geometric primitives.
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An intersection shader for a primitive is executed whenever its axis-aligned
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bounding box is hit by a ray.
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A built-in intersection shader for triangle primitives that is used
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automatically whenever geometry of type ename:VK_GEOMETRY_TYPE_TRIANGLES_NV
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is specified.
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Like other ray tracing shader domains, an intersection shader operates on a
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single ray at a time.
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It also operates on a single primitive at a time.
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It is therefore the purpose of an intersection shader to compute the
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ray-primitive intersections and report them.
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To report an intersection, the shader calls the code:OpReportIntersectionNV
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instruction.
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An intersection shader communicates with any-hit and closest shaders by
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generating attribute values that they can: read.
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Intersection shaders cannot: read or modify the ray payload.
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[[shaders-intersection-execution]]
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=== Intersection Shader Execution
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The order in which intersections are found along a ray, and therefore the
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order in which intersection shaders are executed, is unspecified.
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The intersection shader of the closest AABB which intersects the ray is
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guaranteed to be executed at some point during traversal, unless the ray is
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forcibly terminated.
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[[shaders-any-hit]]
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== Any-Hit Shaders
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The any-hit shader is executed after the intersection shader reports an
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intersection that lies within the current [eq]#[tmin,tmax]# of the ray.
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The main use of any-hit shaders is to programmatically decide whether or not
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an intersection will be accepted.
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The intersection will be accepted unless the shader calls the
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code:OpIgnoreIntersectionNV instruction.
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[[shaders-any-hit-execution]]
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=== Any-Hit Shader Execution
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The order in which intersections are found along a ray, and therefore the
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order in which any-hit shaders are executed, is unspecified.
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The any-hit shader of the closest hit is guaranteed to be executed at some
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point during traversal, unless the ray is forcibly terminated.
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[[shaders-closest-hit]]
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== Closest Hit Shaders
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Closest hit shaders have read-only access to the attributes generated by the
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corresponding intersection shader, and can: read or modify the ray payload.
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They also have access to a number of system-generated values.
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Closest hit shaders can: call code:OpTraceNV to recursively trace rays.
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[[shaders-closest-hit-execution]]
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=== Closest Hit Shader Execution
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Exactly one closest hit shader is executed when traversal is finished and an
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intersection has been found and accepted.
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[[shaders-miss]]
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== Miss Shaders
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Miss shaders can: access the ray payload and can: trace new rays through the
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code:OpTraceNV instruction, but cannot: access attributes since they are not
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associated with an intersection.
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[[shaders-miss-execution]]
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=== Miss Shader Execution
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A miss shader is executed instead of a closest hit shader if no intersection
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was found during traversal.
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[[shaders-callable]]
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== Callable Shaders
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Callable shaders can: access a callable payload that works similarly to ray
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payloads to do subroutine work.
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[[shaders-callable-execution]]
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=== Callable Shader Execution
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A callable shader is executed by calling code:OpExecuteCallableNV from an
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allowed shader stage.
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