Browsing by Subject "Tetrahedralization"

Now showing 1 - 4 of 4

Open Access
Bounding volume hierarchy-tetrahedralization hybrid acceleration structure for ray tracing
(2020-12) Demirci, Serkan
The computational cost of the ray-tracing method is directly proportional to the number of ray-surface intersection tests. The naive ray-tracing algorithm requires O(N) computational cost for the ray-surface intersection calculations where N is the number of primitives in the scene. Ray tracing acceleration data structures like the regular grid, bounding volume hierarchy (BVH), kd-tree, constrained tetrahedralization, has been developed to reduce the number of rayobject intersection tests to speed-up ray tracing. We propose a hybrid acceleration structure, the Bounding Volume HierarchyTetrahedral mesh hybrid (BTH) acceleration structure, that can be used to speedup ray tracing. BTH structure is composed of a BVH hierarchy where some of the leaves of the BVH hierarchy contain tetrahedralizations. We propose an algorithm for the construction of the BTH structure. We describe methods for approximating the average nearest-hit cost of a tetrahedralization, which we use for the construction of BTH. Besides, we can adapt the proposed BTH structure for dynamic scenes with hierarchical motion. We describe a two-level BVH-BTH acceleration structure for rendering animated scenes. We test the proposed BTH structure using various scenes. For some of the experiments, the BTH structure performs better against other acceleration structures in terms of rendering times. We perform experiments for animated scenes. We show that the two-level BTH structure outperforms the two-level BVH structure for the tested dynamic scenes.
Open Access
Hardware-accelerated direct visualization of unstructured volumetric meshes
(2022-07) Şahıstan, Alper
Computational fluid dynamic simulations often produce large clusters of finite ele-ments with non-trivial, non-convex boundaries and uneven distributions among com-pute nodes, posing challenges to compositing during interactive volume rendering. Correct, in-place visualization of such clusters becomes difficult because viewing rays straddle domain boundaries across multiple compute nodes. We propose a GPU-based, scalable, memory-efficient direct volume visualization framework suitable for in situ and post hoc usage. Our approach reduces memory usage of the unstructured volume elements by leveraging an exclusive or-based index reduction scheme and provides fast ray-marching-based traversal without requiring large external data structures built over the elements. Moreover, we present a GPU-optimized deep compositing scheme that allows correct order compositing of intermediate color values accumulated across different ranks that works even for non-convex clusters. Furthermore, we illustrate that we can achieve secondary effects such as shadows and gradient shading using our method for single GPU setups. Our approach scales well on large data-parallel sys-tems and achieves interactive frame rates during visualization. We can interactively render Fun3D Small Mars Lander (14 GB / 798.4 million finite elements) and Huge Mars Lander (111.57 GB / 6.4 billion finite elements) data sets at 14 and 10 frames per second using 72 and 80 GPUs, respectively, on the Frontera supercomputer at The Texas Advanced Computing Center (TACC).
Open Access
Memory-efficient constrained delaunay tetrahedralization of large three-dimensional triangular meshes
(2022-07) Erkoç, Ziya
We propose a divide-and-conquer algorithm that can solve the Constrained De-launay Tetrahedralization (CDT) problem. It consists of three stages: Input Partitioning, Surface Closure, and Merge. We first partition the input into sev-eral pieces to reduce the problem size. We apply 2D Triangulation to close the open boundaries to make new pieces watertight. Each piece is then sent to Tet-Gen [Hang Si, “TetGen, a Delaunay-Based Quality Tetrahedral Mesh Generator”, ACM Transactions on Mathematical Software, Vol. 41, No. 2, Article No. 11, 36 pages, January 2015] for processing. We finally merge each tetrahedral mesh to calculate the final solution. In addition, we apply post-processing to remove vertices we introduced during the input partitioning stage to preserve the in-put triangles. An alternative approach that does not insert new vertices and eliminates the need for post-processing is also possible but not robust. The benefit of our method is that it can reduce memory usage or increase the speed of the process. It can even tetrahedralize meshes that TetGen cannot do due to the memory’s insufficiency. We also observe that this method can increase the overall tetrahedral mesh quality.
Open Access
Multi-level tetrahedralization-based accelerator for ray-tracing animated scenes
(John Wiley & Sons Ltd., 2021-06-01) Aman, Aytek; Demirci, Serkan; Güdükbay, Uğur; Wald, I.
We describe a hybrid acceleration structure for ray tracing. The hybrid structure is a Bounding Volume Hierarchy (BVH) where the leaf nodes are tetrahedralized for a decent ray-surface intersection performance. We use the hybrid acceleration structure (BTH) in a two-level acceleration structure for rendering animated scenes. There is a BVH at the top level in this two-level structure and the proposed hybrid structure (BTH) at the bottom level. We test the proposed two-level structure (BVH-BTH) for various animated scenes and obtained promising results against other acceleration structures in terms of rendering times. The two-level BVH-BTH structure outperforms the two-level BVH structure for the tested dynamic scenes.