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# Objective This PR aims to make it so that we don't accidentally go over `MAX_TEXTURE_IMAGE_UNITS` (in WebGL) or `maxSampledTexturesPerShaderStage` (in WebGPU), giving us some extra leeway to add more view bind group textures. (This PR is extracted from—and unblocks—#8015) ## Solution - We replace the existing `view_layout` and `view_layout_multisampled` pair with an array of 32 bind group layouts, generated ahead of time; - For now, these layouts cover all the possible combinations of: `multisampled`, `depth_prepass`, `normal_prepass`, `motion_vector_prepass` and `deferred_prepass`: - In the future, as @JMS55 pointed out, we can likely take out `motion_vector_prepass` and `deferred_prepass`, as these are not really needed for the mesh pipeline and can use separate pipelines. This would bring the possible combinations down to 8; - We can also add more "optional" textures as they become needed, allowing the engine to scale to a wider variety of use cases in lower end/web environments (e.g. some apps might just want normal and depth prepasses, others might only want light probes), while still keeping a high ceiling for high end native environments where more textures are supported. - While preallocating bind group layouts is relatively cheap, the number of combinations grows exponentially, so we should likely limit ourselves to something like at most 256–1024 total layouts until we find a better solution (like generating them lazily) - To make this mechanism a little bit more explicit/discoverable, so that compatibility with WebGPU/WebGL is not broken by accident, we add a `MESH_PIPELINE_VIEW_LAYOUT_SAFE_MAX_TEXTURES` const and warn whenever the number of textures in the layout crosses it. - The warning is gated by `#[cfg(debug_assertions)]` and not issued in release builds; - We're counting the actual textures in the bind group layout instead of using some roundabout metric so it should be accurate; - Right now `MESH_PIPELINE_VIEW_LAYOUT_SAFE_MAX_TEXTURES` is set to 10 in order to leave 6 textures free for other groups; - Currently there's no combination that would cause us to go over the limit, but that will change once #8015 lands. --- ## Changelog - `MeshPipeline` view bind group layouts now vary based on the current multisampling and prepass states, saving a couple of texture binding entries when prepasses are not in use. ## Migration Guide - `MeshPipeline::view_layout` and `MeshPipeline::view_layout_multisampled` have been replaced with a private array to accomodate for variable view bind group layouts. To obtain a view bind group layout for the current pipeline state, use the new `MeshPipeline::get_view_layout()` or `MeshPipeline::get_view_layout_from_key()` methods.
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doc-valid-idents = ["sRGB", "NaN", "iOS", "glTF", "GitHub", "WebGL", "WebGPU", "GilRs"]
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