169 lines
4.6 KiB
Plaintext
169 lines
4.6 KiB
Plaintext
include::meta/VK_NV_mesh_shader.txt[]
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*Last Modified Date*::
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2018-07-19
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*Contributors*::
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- Pat Brown, NVIDIA
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- Jeff Bolz, NVIDIA
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- Daniel Koch, NVIDIA
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- Piers Daniell, NVIDIA
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- Pierre Boudier, NVIDIA
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This extension provides a new mechanism allowing applications to generate
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collections of geometric primitives via programmable mesh shading.
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It is an alternative to the existing programmable primitive shading
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pipeline, which relied on generating input primitives by a fixed function
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assembler as well as fixed function vertex fetch.
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There are new programmable shader types -- the task and mesh shader -- to
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generate these collections to be processed by fixed-function primitive
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assembly and rasterization logic.
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When the task and mesh shaders are dispatched, they replace the standard
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programmable vertex processing pipeline, including vertex array attribute
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fetching, vertex shader processing, tessellation, and the geometry shader
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processing.
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This extension also adds support for the following SPIR-V extension in
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Vulkan:
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* SPV_NV_mesh_shader
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=== New Object Types
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None.
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=== New Enum Constants
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* Extending elink:VkStructureType:
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** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_MESH_SHADER_FEATURES_NV
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** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_MESH_SHADER_PROPERTIES_NV
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* Extending elink:VkShaderStageFlagBits
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** ename:VK_SHADER_STAGE_TASK_BIT_NV
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** ename:VK_SHADER_STAGE_MESH_BIT_NV
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* Extending elink:VkPipelineStageFlagBits
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** ename:VK_PIPELINE_STAGE_TASK_SHADER_BIT_NV
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** ename:VK_PIPELINE_STAGE_MESH_SHADER_BIT_NV
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=== New Enums
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None.
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=== New Structures
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* slink:VkPhysicalDeviceMeshShaderFeaturesNV
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* slink:VkPhysicalDeviceMeshShaderPropertiesNV
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* slink:VkDrawMeshTasksIndirectCommandNV
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=== New Functions
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* flink:vkCmdDrawMeshTasksNV
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* flink:vkCmdDrawMeshTasksIndirectNV
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* flink:vkCmdDrawMeshTasksIndirectCountNV
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=== New or Modified Built-In Variables
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* <<interfaces-builtin-variables-taskcount,TaskCountNV>>
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* <<interfaces-builtin-variables-primitivecount,PrimitiveCountNV>>
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* <<interfaces-builtin-variables-primitiveindices,PrimitiveIndicesNV>>
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* <<interfaces-builtin-variables-clipdistancepv,ClipDistancePerViewNV>>
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* <<interfaces-builtin-variables-culldistancepv,CullDistancePerViewNV>>
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* <<interfaces-builtin-variables-layerpv,LayerPerViewNV>>
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* <<interfaces-builtin-variables-meshviewcount,MeshViewCountNV>>
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* <<interfaces-builtin-variables-meshviewindices,MeshViewIndicesNV>>
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* (modified)code:Position
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* (modified)code:PointSize
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* (modified)code:ClipDistance
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* (modified)code:CullDistance
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* (modified)code:PrimitiveId
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* (modified)code:Layer
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* (modified)code:ViewportIndex
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* (modified)code:WorkgroupSize
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* (modified)code:WorkgroupId
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* (modified)code:LocalInvocationId
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* (modified)code:GlobalInvocationId
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* (modified)code:LocalInvocationIndex
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* (modified)code:DrawIndex
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* (modified)code:ViewportMaskNV
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* (modified)code:PositionPerViewNV
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* (modified)code:ViewportMaskPerViewNV
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=== New SPIR-V Capability
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* <<spirvenv-capabilities-table-meshshading,MeshShadingNV>>
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=== Issues
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. How to name this extension?
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+
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--
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RESOLVED: VK_NV_mesh_shader
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Other options considered:
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* VK_NV_mesh_shading
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* VK_NV_programmable_mesh_shading
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* VK_NV_primitive_group_shading
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* VK_NV_grouped_drawing
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--
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. Do we need a new VkPrimitiveTopology?
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+
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--
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RESOLVED: NO, we skip the InputAssembler stage
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--
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. Should we allow Instancing?
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+
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--
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RESOLVED: NO, there is no fixed function input, other than the IDs.
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However, allow offsetting with a "first" value.
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--
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. Should we use existing vkCmdDraw or introduce new functions?
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--
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RESOLVED: Introduce new functions.
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New functions make it easier to separate from "programmable primitive
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shading" chapter, less "dual use" language about existing functions having
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alternative behavior.
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The text around the existing "draws" is heavily based around emitting
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vertices.
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--
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. If new functions, how to name?
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+
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--
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RESOLVED: CmdDrawMeshTasks*
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Other options considered:
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* CmdDrawMeshed
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* CmdDrawTasked
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* CmdDrawGrouped
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--
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. Should VK_SHADER_STAGE_ALL_GRAPHICS be updated to include the new stages?
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+
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--
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RESOLVED: No.
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If an application were to be recompiled with headers that include additional
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shader stage bits in VK_SHADER_STAGE_ALL_GRAPHICS, then the previously valid
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application would no longer be valid on implementations that don't support
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mesh or task shaders.
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This means the change would not be backwards compatible.
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It's too bad VkShaderStageFlagBits doesn't have a dedicated "all supported
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graphics stages" bit like VK_PIPELINE_STAGE_ALL_GRAPHICS_BIT, which would
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have avoided this problem.
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--
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=== Version History
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* Revision 1, 2018-07-19 (Christoph Kubisch, Daniel Koch)
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- Internal revisions
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