Given a position x/y in world coordinates I need the same position, but in the local coordinate system of a given group. The group is a child of a chain of other groups that all apply various transformations. How do I get the local position? I'd expect there to be a matrix somewhere to turn global into local coordinates, but I've failed to find it anywhere. At this point my best idea would be to go through the groups and build my own matrix, but that seems like bypassing something