ockham has the best (and most widely used) solution. Parenting is a great method to "isolate" coordinates systems from the world coordinates so that rotation and translation can be calculated with respect to the parent system and not the world system. Otherwise, it get's really, really complex - just try moving and rotating along a vector that doesn't have it's start on the world axis (e.g.: a camera that you want to dolly along it's Z-axis, no matter what orientation it has to the world system), but using world coordinates. BYS