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gpu: Document why VertexID/InstanceID builtins are unreliable

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Ethan Lee
2024-12-24 14:52:32 -05:00
parent dd83908109
commit 65e0fed5b3
1 changed files with 16 additions and 8 deletions
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24
include/SDL3/SDL_gpu.h
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@@ -1419,8 +1419,10 @@ typedef struct SDL_GPUBufferRegion
*
* Note that the `first_vertex` and `first_instance` parameters are NOT
* compatible with built-in vertex/instance ID variables in shaders (for
* example, SV_VertexID). If your shader depends on these variables, the
* correlating draw call parameter MUST be 0.
* example, SV_VertexID); GPU APIs and shader languages do not define these
* built-in variables consistently, so if your shader depends on them, the only
* way to keep behavior consistent and portable is to always pass 0 for the
* correlating parameter in the draw calls.
*
* \since This struct is available since SDL 3.1.3
*
@@ -1439,8 +1441,10 @@ typedef struct SDL_GPUIndirectDrawCommand
*
* Note that the `first_vertex` and `first_instance` parameters are NOT
* compatible with built-in vertex/instance ID variables in shaders (for
* example, SV_VertexID). If your shader depends on these variables, the
* correlating draw call parameter MUST be 0.
* example, SV_VertexID); GPU APIs and shader languages do not define these
* built-in variables consistently, so if your shader depends on them, the only
* way to keep behavior consistent and portable is to always pass 0 for the
* correlating parameter in the draw calls.
*
* \since This struct is available since SDL 3.1.3
*
@@ -3025,8 +3029,10 @@ extern SDL_DECLSPEC void SDLCALL SDL_BindGPUFragmentStorageBuffers(
*
* Note that the `first_vertex` and `first_instance` parameters are NOT
* compatible with built-in vertex/instance ID variables in shaders (for
* example, SV_VertexID). If your shader depends on these variables, the
* correlating draw call parameter MUST be 0.
* example, SV_VertexID); GPU APIs and shader languages do not define these
* built-in variables consistently, so if your shader depends on them, the only
* way to keep behavior consistent and portable is to always pass 0 for the
* correlating parameter in the draw calls.
*
* \param render_pass a render pass handle.
* \param num_indices the number of indices to draw per instance.
@@ -3053,8 +3059,10 @@ extern SDL_DECLSPEC void SDLCALL SDL_DrawGPUIndexedPrimitives(
*
* Note that the `first_vertex` and `first_instance` parameters are NOT
* compatible with built-in vertex/instance ID variables in shaders (for
* example, SV_VertexID). If your shader depends on these variables, the
* correlating draw call parameter MUST be 0.
* example, SV_VertexID); GPU APIs and shader languages do not define these
* built-in variables consistently, so if your shader depends on them, the only
* way to keep behavior consistent and portable is to always pass 0 for the
* correlating parameter in the draw calls.
*
* \param render_pass a render pass handle.
* \param num_vertices the number of vertices to draw.