How to preserve morphTargets informations when using Geometry.fromBufferGeometry()?

Questions
1

I want to compute the vertextNormals of this model to properly using MeshNormalMaterial on it.
I get good result by using BufferGeometry.computeVertexNormals.
The only problem is that it averaging face normals on the bottom cube, what I want is like the upper cube(sharp edge), so I try to use Geometry.computeFlatVertexNormals (which does not exist in BufferGeometry).
But after I use Geometry.fromBufferGeometry(), all the morphTargets informations lost.
Is there any proper way to achieve this requirement?
image

2

I realized that set flatShading=true for MeshNormalMaterial can make the bottom cube correct.
But beause I use this MeshNormalMaterial as scene.overrideMaterial, so I don’t want to change the material but the geometry.

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3

The conversion from BufferGeometry to Geometry was not further enhanced on purpose. There were existing PRs and issues but the request can be considered as a Won't fix (see https://github.com/mrdoob/three.js/pull/14493#issuecomment-405866263).

You can try to call toNonIndexed() on your BufferGeometry so that no vertices are shared anymore. If you then call computeVertexNormals(), the normals won’t be weighted across multiple faces anymore.

4

toNonIndexed() works! Thank you!