GL::Vector4 ray = main_view.get_camera().unproject(GL::Vector4(p.x, p.y, 0, 0));
// XXX Do this better; make this function a template?
GL::Vector4 ray = main_view.get_camera().unproject(GL::Vector4(p.x, p.y, 0, 0));
// XXX Do this better; make this function a template?