Slight fix for triangle assignment to bodypart on partition import

[Candoran2]

@niftools/blender-niftools-addon-reviewer

Overview

1. Added warning for too many bones per partition (since some games will crash with that, I think?) and pulled up the check for this.
2. Fix for issue "Some polygons of Parthurnax not assigned to any body part." error on unmodified model #496 , by allowing for multiple triangles to map from the same vertices when doing the map from partition triangles to the main NiTriShape.

Detailed Description

1. Self-explanatory.
2. Causing the issue was the fact that there were two triangles using the same vertices for this particular mesh, so on import those vertices only mapped to the first triangle. The code has now been changed such that the vertices map to a list of all triangles (in the overwhelming majority of cases just 1) using those vertices. However, that does mean that all triangles sharing the same vertices will end up in the same partition on import, which is not necessary (though always the case in vanilla meshes, as far as I know). Also, it is possible for a triangle to be defined in the main NiTriShape, but not in any of the partitions (again, this does not seem to happen). A true fix would mean that we import skinned shapes from the triangle data in the NiSkinPartition instead of relying on the triangles in the main NiTriShape, though of course this is a lot of work. It will be necessary for SSE meshes when we support those, because there, triangles are only defined in the NiSkinPartition.

Fixes Known Issues

1. "Some polygons of Parthurnax not assigned to any body part." error on unmodified model #496

Documentation

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Testing

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Manual

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Automated

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Additional Information

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[neomonkeus]

Agree with solution provided here to fix the issue is appropriate for current set of supported feature.
Always good to highlight the limitations and at what point the need becomes a must to rework the solution 👍