(s, h, part, w) per vertex; see the module docs.
The first bodyIndexCount indices are the closed body; the rest are fins.
Axis-aligned bounds: [minX, minY, minZ, maxX, maxY, maxZ].
Triangle indices.
Unit normals, xyz per vertex.
xyz per vertex. Fish face +z (nose at z = 0.5, tail tip at z = −0.5), y up.
A mesh as typed arrays.