[Merged by Bors] - Use a sorted Map for vertex buffer attributes #1796
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mtsr
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alice-i-cecile
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C-Performance
DJMcNab
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Apr 3, 2021
crates/bevy_render/src/mesh/mesh.rs
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| @@ -210,7 +210,7 @@ pub struct Mesh { | |||
| primitive_topology: PrimitiveTopology, | |||
| /// `bevy_utils::HashMap` with all defined vertex attributes (Positions, Normals, ...) for this | |||
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Very nice catch! I think this is a reasonable change and I doubt the BTreeMap will register on benchmarks. In fact, hashing the full string might end up being more expensive than BTree insertions when the tree size is small. |
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bors r+ |
bors bot
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Apr 13, 2021
The `VertexBufferLayout` returned by `crates\bevy_render\src\mesh\mesh.rs:308` was unstable, because `HashMap.iter()` has a random order. This caused the pipeline_compiler to wrongly consider a specialization to be different (`crates\bevy_render\src\pipeline\pipeline_compiler.rs:123`), causing each mesh changed event to potentially result in a different `PipelineSpecialization`. This in turn caused `Draw` to emit a `set_pipeline` much more often than needed. This fix shaves off a `BindPipeline` and two `BindDescriptorSets` (for the Camera and for global renderresources) for every mesh after the first that can now use the same specialization, where it didn't before (which was random). `StableHashMap` was not a good replacement, because it isn't `Clone`, so instead I replaced it with a `BTreeMap` which is OK in this instance, because there shouldn't be many insertions on `Mesh.attributes` after the mesh is created.
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Pull request successfully merged into main. Build succeeded: |
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jihiggins
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Apr 18, 2021
The `VertexBufferLayout` returned by `crates\bevy_render\src\mesh\mesh.rs:308` was unstable, because `HashMap.iter()` has a random order. This caused the pipeline_compiler to wrongly consider a specialization to be different (`crates\bevy_render\src\pipeline\pipeline_compiler.rs:123`), causing each mesh changed event to potentially result in a different `PipelineSpecialization`. This in turn caused `Draw` to emit a `set_pipeline` much more often than needed. This fix shaves off a `BindPipeline` and two `BindDescriptorSets` (for the Camera and for global renderresources) for every mesh after the first that can now use the same specialization, where it didn't before (which was random). `StableHashMap` was not a good replacement, because it isn't `Clone`, so instead I replaced it with a `BTreeMap` which is OK in this instance, because there shouldn't be many insertions on `Mesh.attributes` after the mesh is created.
ostwilkens
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Jul 27, 2021
The `VertexBufferLayout` returned by `crates\bevy_render\src\mesh\mesh.rs:308` was unstable, because `HashMap.iter()` has a random order. This caused the pipeline_compiler to wrongly consider a specialization to be different (`crates\bevy_render\src\pipeline\pipeline_compiler.rs:123`), causing each mesh changed event to potentially result in a different `PipelineSpecialization`. This in turn caused `Draw` to emit a `set_pipeline` much more often than needed. This fix shaves off a `BindPipeline` and two `BindDescriptorSets` (for the Camera and for global renderresources) for every mesh after the first that can now use the same specialization, where it didn't before (which was random). `StableHashMap` was not a good replacement, because it isn't `Clone`, so instead I replaced it with a `BTreeMap` which is OK in this instance, because there shouldn't be many insertions on `Mesh.attributes` after the mesh is created.
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The
VertexBufferLayoutreturned bycrates\bevy_render\src\mesh\mesh.rs:308was unstable, becauseHashMap.iter()has a random order. This caused the pipeline_compiler to wrongly consider a specialization to be different (crates\bevy_render\src\pipeline\pipeline_compiler.rs:123), causing each mesh changed event to potentially result in a differentPipelineSpecialization. This in turn causedDrawto emit aset_pipelinemuch more often than needed.This fix shaves off a
BindPipelineand twoBindDescriptorSets(for the Camera and for global renderresources) for every mesh after the first that can now use the same specialization, where it didn't before (which was random).StableHashMapwas not a good replacement, because it isn'tClone, so instead I replaced it with aBTreeMapwhich is OK in this instance, because there shouldn't be many insertions onMesh.attributesafter the mesh is created.