Interactive Rendering of Large Unstructured Grids Using Dynamic Level-of-Detail

Abstract

Figure 1: Volume renderings of the Torso data set with over one million tetrahedra using view-aligned sampling. From left to right: full quality (100% LOD) rendering at 2.0 fps, 25% LOD at 5.3 fps, 10% LOD at 10.0 fps, and 5% LOD at 16.1 fps. ABSTRACTWe describe a new dynamic level-of-detail (LOD) technique that allows real-time rendering of large tetrahedral meshes. Unlike approaches that require hierarchies of tetrahedra, our approach uses a subset of the faces that compose the mesh. No connectivity is used for these faces so our technique eliminates the need for topological information and hierarchical data structures. By operating on a simple set of triangular faces, our algorithm allows a robust and straightforward graphics hardware (GPU) implementation. Because the subset of faces processed can be constrained to arbitrary size, interactive rendering is possible for a wide range of data sets and hardware configurations.

Out‐of‐Core Simplification and Crack‐Free LOD Volume Rendering for Irregular Grids

“…In [CFM*04], a multiresolution representation for tetrahedral meshes is built to support selective refinement queries for visualization. The work [CCSS05] introduced a sample‐based simplification for LOD volume rendering; the simplification is done by sampling the mesh triangle faces with the connectivity removed.…”

“…A progressive volume rendering algorithm [CBPS06] was proposed for the client‐server model, where the client has limited main memory but the preprocessing and the major run‐time computations need to be performed in‐core on the server; only a single resolution is kept for the data. The iRun approach [VCS*07] is an out‐of‐core extension of the sample‐based LOD method [CCSS05], where no connectivity or mesh LOD is maintained. As mentioned in Section 1, [SS06b] performs out‐of‐core simplification and LOD volume rendering for tetrahedral meshes, but it uses the simple approach of not simplifying the sub‐volume boundaries at all.…”

Hardware-Assisted Point-Based Volume Rendering of Tetrahedral Meshes

“…Sampling the original mesh to form new, more amenable representations for level-of-detail strategies is another approach to this problem. Leven et al [12] sample and voxelize the original mesh whereas Callahan et al [3] present a method by which importance sampling of the underlying geometry is used to achieve interactive framerates.…”

“…In particular, level-of-detail (LOD) approaches become much easier. Recently, Callahan et al [3] introduced a simple, dynamicallyadjusting LOD algorithm based on a sample-based simplification of the renderable primitives. Instead of simplifying the geometry, the algorithm performs importance sampling of the primitives, which enables dynamic LOD by adjusting the number of primitives rendered at each frame.…”

“…Since our volume renderer relies heavily on fragment processing, we use an LOD algorithm corresponding to the number of fragments, instead of primitives as in [3]. Thus, a 50% LOD rasterizes 50% of the fragments.…”