solve the deform in rigged mesh brought by no-bone-weight vertex

[Jason0214]

The problem of #36 #37 is that there exists vertex with no bone weights in the mesh.

As reduz said,

the way Godot works (which kind of applies to all modern game engines), unassigned vertices are not really supposed to work

so no-bone-weight vertex brings undefined behavior. I notice there is a fix in collada exporter, I mocked it in this PR, it solve the deform in #36, #37 in rest position, but it is really not robust. For pose it will still has the mesh deformed, as this fix merely assign the vertex to bone with index 0.

I am thinking about assigning no-bone-weight vertices to their neighboring vertex's bones, but what if their neighboring vertices also has no bones ? it will be very time consuming.

need some suggestion on how to solve this.

[Jason0214]

CC @sdfgeoff @mysticfall

[Jason0214]

smooth maybe this smooth of bone weights can be used

[sdfgeoff]

#37 is caused when the exported weights aren't normalized (and so the vertex is partly bound to no bone), and this PR will definitely fix that.

I wouldn't apply any sort of smoothing, because this will change the export from what is visible in blender.

What is curious to me is that blender seems to do something clever. If you go into monster.blend, you'll see that quite a lot of the right-hand foreleg has zero weight, and yet it deforms with the bone.

[Jason0214]

1. explicitly throw error for vertex in rigged mesh without bone weights
2. confirmed Rigged mesh looks deformed when imported to Godot #37 is a normalize problem, it is now solved

[Jason0214]

Unfortunately #43 is not fixed,