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Retain RenderMeshInstance and MeshInputUniform data from frame to frame. #16385

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This commit moves the front end of the rendering pipeline to a retained model when GPU preprocessing is in use (i.e. by default, except in constrained environments). RenderMeshInstance and MeshUniformData are stored from frame to frame and are updated only for the entities that changed state. This was rather tricky and requires some careful surgery to keep the data valid in the case of removals.

This patch is built on top of Bevy's change detection. Generally, this worked, except that ViewVisibility isn't currently properly tracked. Therefore, this commit adds proper change tracking for ViewVisibility. Doing this required adding a new system that runs after all check_visibility invocations, as no single check_visibility invocation has enough global information to detect changes.

On the Bistro exterior scene, with all textures forced to opaque, this patch improves steady-state extract_meshes_for_gpu_building from 93.8us to 34.5us and steady-state collect_meshes_for_gpu_building from 195.7us to 4.28us. Altogether this constitutes an improvement from 290us to 38us, which is a 7.46x speedup.

Screenshot 2024-11-13 143841

Screenshot 2024-11-13 143850

This patch is only lightly tested and shouldn't land before 0.15 is released anyway, so I'm releasing it as a draft.

frame.

This commit moves the front end of the rendering pipeline to a retained
model when GPU preprocessing is in use (i.e. by default, except in
constrained environments). `RenderMeshInstance` and `MeshUniformData`
are stored from frame to frame and are updated only for the entities
that changed state. This was rather tricky and requires some careful
surgery to keep the data valid in the case of removals.

This patch is built on top of Bevy's change detection. Generally, this
worked, except that `ViewVisibility` isn't currently properly tracked.
Therefore, this commit adds proper change tracking for `ViewVisibility`.
Doing this required adding a new system that runs after all
`check_visibility` invocations, as no single `check_visibility`
invocation has enough global information to detect changes.

On the Bistro exterior scene, with all textures forced to opaque,
this patch improves steady-state `extract_meshes_for_gpu_building` from
93.8us to 34.5us and steady-state `collect_meshes_for_gpu_building` from
195.7us to 4.28us. Altogether this constitutes an improvement from 290us
to 38us, which is a 7.46x speedup.
@pcwalton pcwalton added A-Rendering Drawing game state to the screen C-Performance A change motivated by improving speed, memory usage or compile times S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged labels Nov 14, 2024
@alice-i-cecile alice-i-cecile added this to the 0.16 milestone Nov 14, 2024
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A-Rendering Drawing game state to the screen C-Performance A change motivated by improving speed, memory usage or compile times S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged
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2 participants