VectorA = CoordFrameA * VectorB so CoordFrameA is the coordinate frame that VectorB is relative to, expressed in terms of the coordinate frame that VectorA is relative to. there's a way to think about it so there are fewer different frames and vectors everywhere confusing you, not sure what it is. so if the camera is at CoordFrameCamera, and we had something positioned in the world coord frame ....... what does this mean? CoordFrameCamera is the *multiplication* applied to things expressed *relative to the camera* to get to the world frame. WorldVector = CoordFrameCamera * CameraRelativeVector So, to move something to be relative to the camera, we multiply its world location by the inverse of the camera location. I guess it's usual when making a 3d engine to have a class representing a transformable object. Is there a basic operation happening here? We're moving between coordinate frames. If I have two coordinate frames in terms of the world frame .... okay so the basic operations here are expressing a world vector in terms of a local coordinate frame, and a local vector in terms of the world coordinate frame. transforming something to the camera expresses it in terms of the camera coordinate frame.