move the cats(nodes) by clicking and dragging to create the flat 2d shape that will turn into a prism. The prism will render in real-time. Change the zoom to see the final render closer. After changing the zoom click one of the nodes. While this may seem counterintuitive, decrease the zoom to scale the image up.
Whatever you do, don't overlap your nodes. This will result in you losing one of the sides of the shape.