Multithreaded mesh bounds recalculation?

I'm working on a system for deforming meshes and right now the slowest part is the bounds recalculation (I was able to jobify normal recalculation). It would be simple to calculate bounds on a single other thread but I'm curious if it's possible to split the calculation over multiple threads with the job system.

I'm not sure how to do it because each batch can't access the same bounds. I've never ventured beyond IJob and IJobParallelFor, is there another interface that would make this easier? I thought maybe I could deploy a bunch of batches and then have a Bounds instance encapsulate each batches' bounds on the main thread. That way I'm only encapsulating as many bounds as there are threads (roughly) instead of thousands of points. Is what I'm trying to do silly?

 

i'd just try to find minx,miny,minz,maxx,maxy,maz (which probably should work splitted on thread too, haven't used ecs)
and then adjust/make bounds from that?

 

Yea I know how to calculate the bounds, I was just wondering if there was a way to split the calculation across multiple threads or speed it up in some other way. The problem is each thread can't access the same bounds variable at the same time because that will break stuff. [edit] also I'm not using ECS, just the job system.

 

Maybe you ll find inspiration looking at MeshInstanceRender in the latest ECS sources :

AppData\Local\Unity\cache\packages\staging-packages.unity.com\com.unity.entities@0.0.12-preview.13\Unity.Rendering.Hybrid\MeshInstanceRendererSystem.cs

 

Just split the vertices into X chunks (one per thread), calculate bounds per chunk, and then do the min/max of all chunks?

 

That's what I was thinking. Is there a way to automate the splitting with the job system? Similarly to how you tell IJobParallelFor how many operations you want in a batch and it splits the native arrays for you behind the scenes?

 

This is where you define. See number 32

Code (CSharp):

1. protected override JobHandle OnUpdate ( JobHandle inputDeps )
2.     {
3.         return new MyJob
4.         {
5.             data = data
6.         }.Schedule ( data.Length, 32, inputDeps ) ;
7.     }

 

I know how to schedule a job and give it a batch size, but I can't get each batches' uniquely calculated bounds. The end result is a single job and a single version of whatever data was in the job. The goal is to use the job system to calculate the bounds of separate chunks of the mesh and then create one final 'Bounds' instance that encapsulates each batches' chunk's bounds on the main thread.

 

Use use the .NET Task API, it allows you to return values from each batch easily.