)
Transforms from world space to the 'ground' plane of the graph.
The transformation is purely a rotation so no scale or offset is used.
For a graph rotated with the rotation (-90, 0, 0) this will transform a coordinate (x,y,z) to (x,y). For a graph with the rotation (0,0,0) this will tranform a coordinate (x,y,z) to (x,z). More generally for a graph with a quaternion rotation R this will transform a vector V to R * V (i.e rotate the vector V using the rotation R).