   Local to global coordinates
  What's the best way to go from local to global coordinates? I have a scene graph, I know how to create transformation matrices and how matrix multiplication works, but what should I use to construct matrices and perform matrix multiplication?   
  The matrix that converts from coordinate space B ("global") to coordinate space A ("local") is the inverse of the matrix that transforms from A to B. If the matix is orthogonal, this is also the same as the transpose (which is cheaper to compute).   ;  Ah, yes, I know that part, but how is it done in practice? I mean, how can I build matrices and perform necessary calculations (C++/OpenGL)? Libraries? Functions? I'm really lost here.   ;  Generally you use a matrix and vector library, yes.   ;  Check out the alternative libraries forum to find libraries that handle matrix multiplication and so on.You can use GL for this, but I would advise against that as it doesn't look good. GL should ideally be used just for rendering.   