Per-pixel extrusion mapping with correct silhouette

Abstract

Per-pixel extrusion mapping consists of creating a virtual geometry that is stored in a texture over a polygon model without increasing its density. There are four types of extrusion mapping, namely, basic extrusion, outward extru sion, beveled extrusion, and chamfered extrusion. These different techniques produce satisfactory results in the case of plane surfaces, however, when it is about curved surfaces, a silhouette is not visible at the edges of the extruded forms on the 3D surface geometry, as they not take the curvatures of the 3D meshes into account. In this paper, we present an improvement that consists of using curved ray-tracing to correct the silhouette problem by combining per-pixel extrusion-mapping techniques with a quadratic approximation that is computed at each vertex of a 3D mesh.