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.

Real-time Rendering of Small-scale Volumetric Structure on Animated Surfaces

“…The method focuses mostly on cloth rendering in garment prototyping applications. Also there is an approach for cloth rendering on fiber level [8], but it's applicable only for this specific cloth visualization.…”

“…For applying a 3D texture on a base surface we use a real-time adaptation [8] of a method named shell mapping, originally introduced in [4]. Applying is performed by constructing a shell of tetrahedrons over the base surface and then, when rendering, tracing the texture inside each one using sphere tracing [9].…”

Deferred Warping

“…Shen [12] extends Shell Mapping to support the animation of a shell, which allows morphing and deformation of the surface objects. Ritsche [13] presents a real-time version of a shell space rendering approach. The technique uses ray tracing of surface details stored as volumetric textures.…”

Interactive HDR lighting of dynamic participating media

“…1, determines, for each position x inside the data volume, the distance δ(x) to the nearest non-empty voxel. Other authors have used similar approaches to calculate surface displacement [7] or to compute geometry in shell space [36]. In our case, we apply this technique to optimize lighting calculations by accelerating primary and shadow ray traversals.…”