Real-time shell space rendering of volumetric geometry

Abstract

This work introduces a new technique for real-time rendering of arbitrary volumetric geometry into a polygonal mesh's shell space. The shell space is a layer of variable thickness on top or below the polygonal mesh. The technique computes view ray shell geometry intersections in a pixel shader. In addition to arbitrary volumetric shell geometry, represented as volume textures, it can handle also the less general case of height-field shell geometry. To minimize the number of ray tracing steps, a 3D distance map is used for skipping empty space in the shell volume. The shell volume is defined by a pre-computed tetrahedra mesh. The tetrahedra subdivide prisms extruded from the polygonal base mesh. A vertex shader computes tetrahedron face plane distances for generating the per-pixel tetrahedron thickness using non-linear interpolation. The technique includes local lighting and overcomes shortcomings of previous shell space rendering approaches such as high storage requirements and involved per-vertex computations [Wang et al. 2004] or low shell geometry depth complexity and mapping distortions [Policarpo and Oliveira 2006]. Additionally, rendering artifacts for shallow view angles common to many related techniques are reduced. Furthermore, methods for generating a geometry volume texture and the corresponding distance map from a polygonal mesh are presented.