We plan to pass bone weights and indices with custom attributes to Houdini PolyReduce node, and update the output Unity mesh by these custom attributes in the post cook function.

The custom attributes do survive the trip from Houdini, but it's impossible to update the output mesh write the custom attributes because the plugin reindices and combines the submeshes.

We may fetch the custom attributes in the post cook function, but the custom attributes are returned as an array in the order of original vertices or points before reindexing.

We have thought about some workarounds:
1. Passing the bone weights and indices via unused standard attributes. The candidates are color, uv2, and uv3 (the plugin supports only 3 UVs), and we need two 4-element-vectors. This approach doesn't work if all the standard attributes are occupied.
2. Modifying the plugin code. In this case we would like to make a contribution, but I'd like to know whether you have already planned it already, or whether you already have some general design in mind.

The new feature Attribute Store (18.0.311) doesn't resolve this problem neither.

2nd options seems the best. Feel free to make the contribution directly here, or via the github page: https://github.com/sideeffects/HoudiniEngineForUnity [github.com]