The origin of this example arrow is at the upper end of the arrow (x=0, y=1, z=0). You want to place the new origin (the yCenter origin) in the center of the arrow body, at y=0.5 (instead of y=1). When the script is executed (execution order from left to right in the picture), yCenterA lifts the prop geometry by y=0.5. The center of the arrow body moves from y=0.5 to y=1. Next, the OffsetA channels are evaluated, and the Poser Origin becomes the center of rotation. Next, the rotations are evaluated. Since the center of this rotation is also the center of the arrow body, the arrow rotates around its center. Next, yCenterB is evaluated, which resets the yCenterA translation. So, yCenterB lowers the prop geometry by y=-0.5, and the center of the arrow body moves back to the previous position from y=1 to y=0.5. Finally, the OffsetB channels reset the default origin, and the scene is rendered. The yCenterA and yCenterB translations are invisible: They are both evaluated, before the scene is rendered, and both motions cancel each other out, so the prop is at the same y position before and after the scene update. When you look at the arrow after the channel evaluation (rightmost in the picture), you cannot really see where the rotation center was. Could be the green cross, or the green dot. You can't see the center of rotation in this picture, because you don't see any "world coordinates", so you can't decide where the arrow is in the end. The rotation center depends on your point of view, and it's all a question of positioning the prop in the scene. The green cross displayed by the Joint Editor and the "Display Origin" option is the Poser Origin. The green cross doesn't move, when the new yCenter origin is set. The green cross reflects the origin data stored in the "origin" line of the code, which is not modified by the yCenter channels. When you display the green cross, and rotate the prop around a new yCenter origin, the Poser Origin seems to orbit the new center of rotation. What you see is in fact an optical delusion caused by the yCenter translations during the script evaluation.