# Objective

- Speed up `collect_meshes_for_gpu_building`, a bottleneck for scenes
with many moving meshes.

## Solution

- Parallelize the gather step for mesh collection.
- Immediately start up a task for serial collection of meshes, which
cannot be parallelized.
- Spawn many tasks for gathering meshes, and send batches of these to
the collection task
- This allows the serial collection step to start immediately, instead
of being delayed until after all collection is finished.

## Testing

- Built a new `bevymark_3d` stress test for benchmarking dynamic 3d mesh
scenes. This is not currently covered by our stress tests.
#22298
- With 200k meshes, this drops total frame times from 16.4ms to 12.3ms
(-4.1ms)

<img width="631" height="377" alt="image"
src="https://github.com/user-attachments/assets/ff9de860-e1f2-4f98-8075-0b3720a82913"
/>

- Mesh collection itself drops from 7.9ms to 3.6ms (-4.3ms)

<img width="623" height="372" alt="image"
src="https://github.com/user-attachments/assets/cf52687a-503b-4f70-8e99-0ad2e63f4da0"
/>