Imagine a solar system: Planets rotating around the sun, satellites rotating around the planets. The planets have an distance from the sun and the satellites an distance from a planet were they rotating around. Code example: // Set planet glTranslatef(fDistance, 0.0f, 0.0f); glRotatef(fAngle, 0.0f, 0.0f, 1.0f); // Set satellite: glTranslatef(fDistance, 0.0f, 0.0f); glRotatef(fAngle, 0.0f, 0.0f, 1.0f); ... How could I compute the ''real'' world positon of a satellite? (I need it for the collision detection) Maybe with the modelview matrix? If yes, how??