Animating impossible figure from twisted torus to penrose stairs

When a start prism and an end prism's vertices are in the same values on the projection screen, the shape model is viewed as an impossible figure. Therefore, if we can create the optical illusion object according to an arbitrary viewpoint, it is possible to create impossible figure that is viewed from the arbitrary viewpoint. We have already proposed and developed a method which animates impossible rectangle twisted torus figure from any viewpoint interactively and in real time[Nakatsu, et al. 2012]. Although the method of creating an optical illusion based on the optical illusion objects is a simple and classic method, this is powerful and robust all the more. Even when a viewpoint is moved to a wide range of area, the animation of an impossible figure can be created. We have extended the application of this principle to Penrose Stairs, and this paper presents that it was successfully realized when the viewpoint was moved freely.