Import: primitives add too many vertices

[scurest]

If a primitive has N elements in its POSITION accessor, N vertices always get added to the mesh, even if the indices accessor is, say, [0, 1, 2], so there should actually only be three vertices. This can result in a huge explosion in vertex count.

JoeyVrowl originally noticed this issue and made a test file. See KhronosGroup/UnityGLTF#197, ksons/gltf-blender-importer#29.

Taking apart a corner reveals many extra verts.

[scurest]

@julienduroure The vertex count looks good! Two things:

1. This breaks the model from Import: distorted animation on joint with node scale of -1 #257. Possibly you need to do something for joints/weights/vertex colors too?
2. This doesn't only happen when the indices and vertices have different lengths. A quad has indices [0,1,2,2,3,0] with length six but only makes four vertices.

[julienduroure]

OK, should avoid to code late during the night ... I checked for normals & UV, but forget to check skinning ...

[scurest]

Skinning is fixed! But not vertex colors :)

[julienduroure]

And probably not morphs target too!

[julienduroure]

@scurest I pushed some fixes, can you please test again?
Thanks for pointing this :)

[scurest]

I can confirm vertex colors are fixed!

Unfortunately I have no models that use morph targets, so I can't confirm they work, but the code for them looks good.