103 lines
3.1 KiB
Plaintext
103 lines
3.1 KiB
Plaintext
// Copyright (c) 2016-2017 Khronos Group. This work is licensed under a
|
|
// Creative Commons Attribution 4.0 International License; see
|
|
// http://creativecommons.org/licenses/by/4.0/
|
|
|
|
include::meta/VK_KHR_shader_draw_parameters.txt[]
|
|
|
|
*Last Modified Date*::
|
|
2016-10-05
|
|
*IP Status*::
|
|
No known IP claims.
|
|
*Interactions and External Dependencies*::
|
|
- Requires the
|
|
https://www.khronos.org/registry/spir-v/extensions/KHR/SPV_KHR_shader_draw_parameters.html[+SPV_KHR_shader_draw_parameters+]
|
|
SPIR-V extension.
|
|
- Requires
|
|
https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_shader_draw_parameters.txt[+GL_ARB_shader_draw_parameters+]
|
|
for GLSL source languages.
|
|
*Contributors*::
|
|
- Daniel Koch, NVIDIA Corporation
|
|
- Jeff Bolz, NVIDIA
|
|
- Daniel Rakos, AMD
|
|
- Jan-Harald Fredriksen, ARM
|
|
- John Kessenich, Google
|
|
- Stuart Smith, IMG
|
|
|
|
This extension adds support for the following SPIR-V extension in Vulkan:
|
|
|
|
* +SPV_KHR_shader_draw_parameters+
|
|
|
|
The extension provides access to three additional built-in shader variables
|
|
in Vulkan:
|
|
|
|
* code:BaseInstance, which contains the pname:firstInstance parameter
|
|
passed to draw commands,
|
|
* code:BaseVertex, which contains the pname:firstVertex/pname:vertexOffset
|
|
parameter passed to draw commands, and
|
|
* code:DrawIndex, which contains the index of the draw call currently
|
|
being processed from an indirect draw 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:
|
|
|
|
* `in int gl_BaseInstanceARB;` -> code:BaseInstance,
|
|
* `in int gl_BaseVertexARB;` -> code:BaseVertex, and
|
|
* `in int gl_DrawIDARB;` -> code:DrawIndex.
|
|
|
|
=== New Object Types
|
|
|
|
None.
|
|
|
|
=== New Enum Constants
|
|
|
|
None.
|
|
|
|
=== New Enums
|
|
|
|
None.
|
|
|
|
=== New Structures
|
|
|
|
None.
|
|
|
|
=== New Functions
|
|
|
|
None.
|
|
|
|
=== New Built-In Variables
|
|
|
|
* <<interfaces-builtin-variables-baseinstance,code:BaseInstance>>
|
|
* <<interfaces-builtin-variables-basevertex,code:BaseVertex>>
|
|
* <<interfaces-builtin-variables-drawindex,code:DrawIndex>>
|
|
|
|
=== New SPIR-V Capabilities
|
|
|
|
* <<spirvenv-capabilities-table-drawparameters,DrawParameters>>
|
|
|
|
=== Issues
|
|
|
|
1) Is this the same functionality as +GL_ARB_shader_draw_parameters+?
|
|
|
|
*RESOLVED*: It's actually a superset as it also adds in support for arrayed
|
|
drawing commands.
|
|
|
|
In GL for +GL_ARB_shader_draw_parameters+, code: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 code:baseVertex parameter, the value of
|
|
code:gl_BaseVertexARB is zero.
|
|
This means that code:gl_BaseVertexARB = code:baseVertex (for
|
|
code:glDrawElements commands with code:baseVertex) or 0.
|
|
In particular there are no code:glDrawArrays commands that take a
|
|
code:baseVertex parameter.
|
|
|
|
Now in Vulkan, we have code:BaseVertex = pname:vertexOffset (for indexed
|
|
drawing commands) or pname:firstVertex (for arrayed drawing commands), and
|
|
so Vulkan's version is really a superset of GL functionality.
|
|
|
|
=== Version History
|
|
|
|
* Revision 1, 2016-10-05 (Daniel Koch)
|
|
- Internal revisions
|