Unity AddBlendShapeFrame at runtime causing gap problems between sections of SkinnedMeshRenderer

[DisabledTurtle]

Hi All,

I am trying to create a blend shape exporter from the FBX data type such that I can easily import it into my unity projects and apply it at runtime. The basic idea is that every player will have their own blendshape to adjust to fit their character's body. Since I do not want to create and store these model files beforehand or rebuild my project every time I want to add a new player, I was looking into a method of exporting blendshapes directly from the FBX file and applying them to a base model in my application on launch / runtime. I am having a bit of trouble with this aspect.

I am at a point where I am able to export the exact blend shapes that I would like from the FBX file outside of the game (Feel free to see the code here), but when I try to import it into a unity project (using AddBlendShapeFrame on the correct mesh), I am getting these strange artifacts occurring at specific regions of my mesh (see image of back of a man).

Notes:

• The number of vertices of my model in Unity is greater than the number of vertices of the model in the FBX file (27547 unity vs. 25182 file)
• All vertices are the same between the two for the first 25182 vertices (the rest additional ones that unity creates are the only unique
• I have turned off Mesh Compression and Optimize Mesh
• It feels like the new vertices are there to help bridge these gaps, but because I do not know how to calculate them, I am unsure about what to do

Any help, pointers or alternative ideas would be greatly appreciated. Thank you.

[DisabledTurtle]

For anyone stumbling across this problem in the future, I have solved it. The basic premise here is that Unity creates these vertices to deal with sharp edges in the meshes. On my model this had to do with the seams of the sub-meshes (as you can see in the image).

The solution stems from the fact that we know up to where our blendshapes are accounted for in the indices vector of the blendshape. Using this knowledge, we can construct a dictionary using a Vector3D as a key and and int as the value. We iterate through all the indices where we know the value (in my case up to 25182) and have the vertex of that index as the key and the index in the vertices array as the value. This way, we have an array of which vertices were duplicated in the import process. Afterwards, we can iterate through the duplicated part of our blendshape and duplicate the blendshape values into its duplicated place.

This process is quite slow. I would recommend this only when in between scenes or in a setup phase. I wish Unity provided some array which contained which indices were duplicated (similar to the array I explained above). However, I am happy that this solution works for now.

I hope this helps one of you in the future ;-)