I believe neither planes nor texture vecs are used anymore in the WMB Format. But anyway, a plane is defined by either a point and a normal, or a distance and a normal. The distance is to the origin. You can convert the point to the distance and vice versa. The texture vectors define a plane in the texture space - a cut through a hypothetical 3D cube that consists of the texture pixels. What the texture_abs_vecs do is unknown to me.