For a clip demonstrating the range of motion of a valve, I created geometric elements. An outer ring shows the arc of the handle, while “sunburst” arms represent regular divisions of the various possible settings that the valve can be turned to in order to control the flow of water. The sunburst arms are scaled one after another in sequence as the valve handle sweeps over them, so they extend from “within” the axis of the valve to the outer arc. This diagrammatic geometry was rendered as a separate layer that could be placed above the background but underneath the valve in the compositing software, where its opacity could also be keyframed.