# Objective
Working with a large number of entities with `Aabbs`, rendered with an instanced shader, I found the bottleneck became the frustum culling system. The goal of this PR is to significantly improve culling performance without any major changes. We should consider constructing a BVH for more substantial improvements.
## Solution
- Convert the inner entity query to a parallel iterator with `par_for_each_mut` using a batch size of 1,024.
- This outperforms single threaded culling when there are more than 1,000 entities.
- Below this they are approximately equal, with <= 10 microseconds of multithreading overhead.
- Above this, the multithreaded version is significantly faster, scaling linearly with core count.
- In my million-entity-workload, this PR improves my framerate by 200% - 300%.
## log-log of `check_visibility` time vs. entities for single/multithreaded
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## Changelog
Frustum culling is now run with a parallel query. When culling more than a thousand entities, this is faster than the previous method, scaling proportionally with the number of available cores.
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