Update subset of vertices of a Mesh

[AlgoryxJosef]

If I have understood the API correctly, it is currently only possible to update ALL vertices of a mesh at once.
We have a situation where we have a very large mesh where a few vertices will change often.

I have a few questions:

1. Is it possible to handle this with the current API while getting good performance?
2. If not, do you have any hints on how the implementation may be changed to support updating a subset of vertices of a mesh?

Regarding question 2 I assume the difficult thing is that vertex data is written to the GPU, is it hard to update a subset of vertices there?

Keep up the good work,
Best regards,
Josef

[prybicki]

Hi @AlgoryxJosef!

If I have understood the API correctly, it is currently only possible to update ALL vertices of a mesh at once.

Yes, your understanding is correct. It was developed as an easier alternative to GPU-skinning, which we would like to implement in the future.

Is it possible to handle this with the current API while getting good performance?

1. An easy thing to try would be to replace OPTIX_BUILD_FLAG_PREFER_FAST_TRACE with OPTIX_BUILD_FLAG_PREFER_FAST_BUILD here and recompiling the library.
2. You could also consider splitting the mesh on the client side to put the fast-changing parts into a separate mesh.

If not, do you have any hints on how the implementation may be changed to support updating a subset of vertices of a mesh?

This could be achieved by adding another API call which would take only the subset of vertices (be it continguous range or a list of indices) and copy only those vertices. However, while this method would reduce the amount of data copied to the GPU, it would not change the cost of re-building OptiX acceleration structure, which may be actually bigger than the copy itself. Optimizing the OptiX AS re-build is far more difficult.

Keep up the good work

Thank you! We'd be happy to hear more details about your use-case, if possible.
Also, please feel free to reach out for commercial support to [email protected].

[AlgoryxJosef]

Thank you for the quick answer, it is really helpful.
I don't have any further questions at the moment, but may have in the future.
All the best,
Josef