Adaptive view dependent tessellation of displacement maps

Abstract

Displacement Mapping is an effective technique for encoding the high levels of detail found in today's triangle based surface models. Extending the hardware rendering pipeline to be capable of handling displacement maps as geometric primitives, will allow highly detailed models to be constructed without requiring large numbers of triangles to be passed from the CPU to the graphics pipeline. We present a new approach based on recursive tessellation that adapts to the surface complexity described by the displacement map. We also ensure that the resolution of the displaced mesh is tessellated with respect to the current view point. Our tessellation scheme performs all tests only on triangle edges to avoid generating cracks on the displaced surface. The main decision for vertex insertion is based on two comparisons involving the average height surrounding the vertices and the normals at the vertices. Individually, the tests will fail to tessellate a mesh satisfactorily, but their combination achieves good results.We propose several additions to the typical hardware rendering pipeline in order to achieve displacement map rendering in hardware. The mesh tessellation is placed within the rendering pipeline so that we can take advantage of the pre-existing vertex transformation units to perform the setup calculations for our view dependent test. Our method adds only simple arithmetic and comparison operations to the graphics pipeline and makes use of existing units for calculations wherever possible.

Displacement patches for view-dependent rendering

“…Little work has been done to deal with general 3D models. The programmable GPU and displacement maps were used to approximate general meshes [32,33] and for adaptive real-time rendering [34][35][36]. Livny et al [2] developed a GPU-based adaptive real-time rendering, which is the short conference version of this paper.…”

Rendering surface details with diffusion curves

“…In practice this means that one side of the cusp might not appear perfectly smooth. Another issue is that the texture warping function only takes the base surface into account, but not the actual displacement, like methods specifically designed for displacement mapping [Moule and McCool 2002;Doggett and Hirche 2000;Gumhold and Huettner 1999]. Because of this, artifacts are sometimes introduced at sharp object corners and large displacements when the displaced surfaces should be visible, but the base surface is not.…”

Seamless patches for GPU-based terrain rendering

“…Other frameworks for displacement maps on programmable graphics hardware have been suggested by [Dog00a,Gum99a,Los04a,Mou02a]. Although these approaches are not implemented at GPU, they are based on designs which prefer many simple computations over a few complicated ones.…”