NOTE! This will not just return m_pParent, when that is
need use it! There is one exception to it, when the parent is
the top-node (the object that isn't a real object), this
will return NULL, so that the top-node's children are
seemingly parentless.
Similar to GetBoneID, but only returns a value for the most important (first)
nonstandard-skeleton bone for each standard bone; returns -1 in other cases.
GetTexGenMatrix: If BeginPass returns STREAM_TEXGENTOUVx, the caller must
call this function to query the texture matrix that will be used to transform
vertex positions into texture coordinates.