When creating graphic libraries you most likely end up dealing with points and rectangles. If you're particularly unlucky, you may end up dealing with affine matrices and 2D transformations. If you're writing a graphic library with 3D transformations, though, you are going to hit the jackpot: 4x4 matrices, projections, transformations, vectors, and quaternions. Most of this stuff exists, in various forms, in other libraries, but it has the major drawback of coming along with the rest of those libraries, which may or may not be what you want. Those libraries are also available in various languages, as long as those languages are C++; again, it may or may not be something you want.