Abstract of Presentation

NURBS have become the de facto standard for representing geometry in engineering. We show how to exploit their rational character also in art-oriented applications, for designing anamorphic images and Escher-like impossible objects. In an optical anamorphosis, an object is seen distorted unless the viewer is positioned at a specific point. To generate an anamorphic version of an initial object, just move its NURBS control points in a radial direction through the viewpoint and simultaneously change their weights.

This effect can also be achieved by employing a FFD (Free-Form Deformation) technique. An anamorphic deformation alters the normals to the faces and hence shading, but the introduction of textures deceives the eye and helps conceal this artifact. With a clever design, it is possible to create NURBS objects that, when seen from a specific vantage point, result in a (seemingly) contradictory 3D geometry. Traditionally, impossible objects are generated by taking an initial 3D model, cutting it, and deforming disconnected faces.

We explore a more elegant, seamless approach, where the initial model continuously deforms in anamorphic fashion, so that straight edges or silhouettes are still perceived as straight.