Add an explainer for GPULimits #482
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In shaders there are several texture types for each dimensionality depending on their component type. It can be either float, uint or sint, with maybe in the future depth/stencil if WebGPU allows reading such textures. The component type of a GPUTextureView's format must match the component type of its binding in the shader module. This is for several reasons: - Vulkan requires the following: "The Sampled Type of an OpTypeImage declaration must match the numeric format of the corresponding resource in type and signedness, as shown in the SPIR-V Sampled Type column of the Interpretation of Numeric Format table, or the values obtained by reading or sampling from this image are undefined." - It is also required in OpenGL for the texture units to be complete, a uint or sint texture unit used with a non-nearest sampler is incomplete and returns black texels. Similar constraints must exist in other APIs. To encode this compatibility constraint, a new member is added to GPUBindGroupLayoutBinding that is a new enum GPUTextureComponentType that give the component type of the texture.
This is the most common case and avoids having an optional dictionary member with no default value (but that still requires a value for texture bindings).
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Part of #483 |
design/Limits.md
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| Limit | API Doc | gpuweb issue/PR | ||
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| `maxBindGroups = 4;` | [Vulkan](https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/vkspec.html#limits-minmax) `maxBoundDescriptorSets` | |
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unfortunate that Vulkan spec is so heavy
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I thought it would at least redirect to the specific section. :(
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It does for me, if I don't touch it while it's loading.
How about the LunarG chunked version?
https://vulkan.lunarg.com/doc/view/latest/linux/chunked_spec/chap36.html#limits-minmax
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design/Limits.md
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| Limit | API Doc | gpuweb issue/PR | ||
| --- | --- | --- | ||
| `maxBindGroups = 4;` | [Vulkan](https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/vkspec.html#limits-minmax) `maxBoundDescriptorSets` | | ||
| `maxDynamicUniformBuffersPerPipelineLayout = 8;` | [Vulkan](https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/vkspec.html#limits-minmax) `maxDescriptorSetUniformBuffersDynamic` | [#406](https://github.com/gpuweb/gpuweb/issues/406) |
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Also, a bit strange to see all of the links pointing to Vulkan
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Makes sense considering Vulkan's lower-end Android hardware support. But the theory is that future limits won't be decided by Vulkan
Co-Authored-By: Kai Ninomiya <[email protected]>
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please link to the chunked spec as @kainino0x suggested!
In the future, we'll need to get a good sense on what the internal needs are for the implementations, which could affect the exposed limits.
This explainer will track the rationale behind each WebGPU limit. All queryable restrictions should have a corresponding reason in this doc.
Edit: Rendered