The "Origin" or "Center Point" can be defined either in the Joint Editor, or via the "Display Origin" option of a prop, and the "Origin" dials in the dial palette. If the arrow prop should rotate around the bottom end, the origin coordinates are x=0, y=0, z=0. If the arrow should rotate around the top, the origin is set to x=0, y=1, z=0. You can store the coordinates for one origin of a prop or actor. Once the origin is defined, you can animate the position of the model and rotate the model around the origin. But when you try to use the "Origin" dials to animate the origin of a prop, you will see that the origin setting changes throughout the entire animation. So, a prop has one non-animatable origin.