Physically Interacting With Four Dimensions

Thesis (Ph.D.) - Indiana University, Computer Sciences, 2009People have long been fascinated with understanding the fourth dimension. While making pictures of 4D objects by projecting them to 3D can help reveal basic geometric features, 3D graphics images by themselves are of limited value. For example, just as 2D shadows of 3D curves may have lines crossing one another in the shadow, 3D graphics projections of smooth 4D topological surfaces can be interrupted where one surface intersects another. The research presented here creates physically realistic models for simple interactions with objects and materials in a virtual 4D world. We provide methods for the construction, multimodal exploration, and interactive manipulation of a wide variety of 4D objects. One basic achievement of this research is to exploit the free motion of a computer-based haptic probe to support a continuous motion that follows the \emph{local continuity\/} of a 4D surface, allowing collision-free exploration in the 3D projection. In 3D, this interactive probe follows the full local continuity of the surface as though we were in fact \emph{physically touching\/} the actual static 4D object. Our next contribution is to support dynamic 4D objects that can move, deform, and collide with other objects as well as with themselves. By combining graphics, haptics, and collision-sensing physical modeling, we can thus enhance our 4D visualization experience. Since we cannot actually place interaction devices in 4D, we develop fluid methods for interacting with a 4D object in its 3D shadow image using adapted reduced-dimension 3D tools for manipulating objects embedded in 4D. By physically modeling the correct properties of 4D surfaces, their bending forces, and their collisions in the 3D interactive or haptic controller interface, we can support full-featured physical exploration of 4D mathematical objects in a manner that is otherwise far beyond the real-world experience accessible to human beings

Haptic Exploration of Mathematical Knots

Abstract. We present a novel multi-modal haptic interface for sketching and exploring the structure and properties of mathematical knots. Our interface derives from the familiar pencil-and-paper process of drawing 2D knot diagrams to facilitate the creation and exploration of mathematical knots; however, with a touch-based interface, users can also leverage their physical intuition by seeing, touching, and feeling the knots. The pure haptic component provides an intuitive interaction model for exploring knots, focusing on resolving the apparent conflict between the continuous structure of the actual knot and the visual discontinuities at occlusion boundaries. The auditory component adds redundant cues that emphasize the traditional knot crossings, where the haptic proxy crosses a visual disruption in the graphics image. Our paradigm enhances and extends traditional 2D sketching methods by exploiting both touch and sound to assist in building clearer mental models of geometry such as knot structures.