oRel can be used to calculate the motion of one object relative to another in the scene.

Steps

1. Select the proximal object in the scene (the object that you want to calculate motion relative to) and click "Insert Selection."
2. Select the distal object in the scene (the object that you want to calculate the relative motion of) and click "Insert Selection."
3. Replace the "m" text under Output Node with the name you would like to give your resulting data node.
4. Click "Output relative data."
5. Click "Close" to exit the dialog box.

This creates a data node with rotations and translations that can be viewed in the Graph Editor.