Deprecation state
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Promoted to Vulkan 1.1
Contact
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Daniel Koch dgkoch
Other Extension Metadata
- Last Modified Date
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2017-09-05
- IP Status
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No known IP claims.
- Interactions and External Dependencies
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-
This extension requires
SPV_KHR_shader_draw_parameters -
This extension provides API support for
GL_ARB_shader_draw_parameters -
Promoted to Vulkan 1.1 Core
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- Contributors
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Daniel Koch, NVIDIA Corporation
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Jeff Bolz, NVIDIA
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Daniel Rakos, AMD
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Jan-Harald Fredriksen, ARM
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John Kessenich, Google
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Stuart Smith, IMG
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Description
This extension adds support for the following SPIR-V extension in Vulkan:
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SPV_KHR_shader_draw_parameters
The extension provides access to three additional built-in shader variables in Vulkan:
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BaseInstance, containing thefirstInstanceparameter passed to drawing commands, -
BaseVertex, containing thefirstVertexorvertexOffsetparameter passed to drawing commands, and -
DrawIndex, containing the index of the draw call currently being processed from an indirect drawing call.
When using GLSL source-based shader languages, the following variables from
GL_ARB_shader_draw_parameters can map to these SPIR-V built-in
decorations:
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in int gl_BaseInstanceARB;→BaseInstance, -
in int gl_BaseVertexARB;→BaseVertex, and -
in int gl_DrawIDARB;→DrawIndex.
Promotion to Vulkan 1.1
All functionality in this extension is included in core Vulkan 1.1.
However, the shaderDrawParameters
feature bit was added to distinguish whether it is actually available or
not.
New Enum Constants
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VK_KHR_SHADER_DRAW_PARAMETERS_EXTENSION_NAME -
VK_KHR_SHADER_DRAW_PARAMETERS_SPEC_VERSION
Issues
1) Is this the same functionality as GL_ARB_shader_draw_parameters?
RESOLVED: It is actually a superset, as it also adds in support for arrayed drawing commands.
In GL for GL_ARB_shader_draw_parameters, gl_BaseVertexARB holds the
integer value passed to the parameter to the command that resulted in the
current shader invocation.
In the case where the command has no baseVertex parameter, the value of
gl_BaseVertexARB is zero.
This means that gl_BaseVertexARB = baseVertex (for
glDrawElements commands with baseVertex) or 0.
In particular there are no glDrawArrays commands that take a
baseVertex parameter.
Now in Vulkan, we have BaseVertex = vertexOffset (for indexed
drawing commands) or firstVertex (for arrayed drawing commands), and
so Vulkan’s version is really a superset of GL functionality.
Document Notes
For more information, see the Vulkan Specification
This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.