Interactive Ray Tracing at Utah SCI Institute Render Group -- render@sci.utah

1. Interactive Ray Tracing at Utah SCI Institute Render Group -- render@sci.utah.edu Ray Tracing Deformable Scenes using Dynamic Bounding Volume Hierarchies Ingo Wald, Solomon Boulos, and Peter Shirley ACM Transactions on Graphics 26(1), 2007 The most significant deficiency of most of todayﾕs interactive ray tracers is that they are restricted to static walkthroughs. This restriction is due to the static nature of the acceleration structures used. While the best reported frame-rates for static geometric models have been achieved using carefully constructed kd-trees, this paper shows that bounding volume hierarchies (BVHs) can be used to efficiently ray trace large static models. More importantly, the BVH can be used to ray trace deformable models (sets of triangles whose positions change over time) with little loss of performance. A variety of efficiency techniques are used to achieve this performance, but three algorithmic changes to the typical BVH algorithm are mainly responsible. First, the BVH is built using a variant of the ﾒsurface area heuristicﾓ conventionally used to build kd-trees. Second, the topology of the BVH is not changed over time so that only the bounding volumes need be re-fit from frame to frame. Third, and most importantly, packets of rays are traced together through the BVH using a novel integrated packet-frustum traversal scheme. This traversal scheme elegantly combines the advantages of both packet traver- sal and frustum traversal, and allows for rapid hierarchy descent for packets that hit bounding volumes, as well as rapid exits for packets that miss. A BVH-based ray tracing system using these techniques is shown to achieve performance for deformable models comparable to that previously available only for static models. Ray Tracing Animated Scenes using Coherent Grid Traversal Ingo Wald, Thiago Ize, Andrew Kensler, Aaron Knoll, and Steven G Parker ACM Transactions on Graphics, 2006, pages 485-493, (Proceedings of ACM SIGGRAPH 2006) We present a new approach to interactive ray tracing of moderate-sized animated scenes based on traversing frustum-bounded packets of coherent rays through uniform grids. By incrementally computing the overlap of the frustum with a slice of grid cells, we accelerate grid traversal by more than a factor of 10, and achieve ray tracing performance competitive with the fastest known packet-based kd-tree ray tracers. The ability to efficiently rebuild the grid on every frame enables this performance even for fully dynamic scenes that typically challenge interactive ray tracing systems. Interactive Isosurface Ray Tracing of Large Octree Volumes Aaron Knoll, Ingo Wald, Steven G Parker, and Charles D Hansen Proceedings of the 2006 IEEE Symposium on Interactive Ray Tracing, 2006, pages 115-124 We present a technique for ray tracing isosurfaces of large com- pressed structured volumes. Data is first converted into a lossless- compression octree representation that occupies a fraction of the original memory footprint. An isosurface is then dynamically ren- dered by tracing rays through a min/max hierarchy inside interior octree nodes. By embedding the acceleration tree and scalar data in a single structure and employing optimized octree hash schemes, we achieve competitive frame rates on common multicore architec- tures, and render large time-variant data that could not otherwise be accomodated. Design for Parallel Interactive Ray Tracing Systems. J. Bigler, A. Stephens and S. G. Parker Proceedings of the IEEE Symposium on Interactive Ray Tracing, 2006, pp. 187-196 We describe the software architecture of the Manta interactive ray tracer and describe its application in engineering and scientific visualization. Although numerous ray tracing software packages have been developed, much of the traditional design wisdom needs to be updated to provide support for interactivity, high degrees of parallelism, and modern packet-based acceleration structures. We dis- cuss situations that are normally not considered when designing a batch ray tracer, and present methods to overcome those challenges. This paper advocates a forward looking programming model for interactive ray tracing that uses reconfigurable components to achieve flexibility while achieving scalability on large numbers of processors. Manta employs data structures motivated by modern micro- processor design that can exploit instruction-level parallelism. We discuss the design tradeoffs and the performance achieved for this system. An Application of Scalable Massive Model Interaction using Shared Memory Systems A. Stephens, S. Boulos, J. Bigler, I. Wald, and S. G. Parker Proceedings of the Eurographics Symposium on Parallel Graphics and Visualization, 2006 During the end-to-end digital design of a commercial airliner, a massive amount of geometric data is produced. This data can be used for inspection or maintenance throughout the life of the aircraft. Massive model interac- tive ray tracing can provide maintenance personnel with the capability to easily visualize the entire aircraft at once. This paper describes the design of the renderer used to demonstrate the feasibility of integrating interactive ray tracing in a commercial aircraft inspection and maintenance scenario. We describe the feasibility demonstra- tion involving actual personnel performing real-world tasks and the scalable architecture of the parallel shared memory renderer. Optimizing Ray-Triangle Intersection via Automated Search Andrew Kensler and Peter Shirley Proceedings of the 2006 IEEE Symposium on Interactive Ray Tracing Sep 2006, p. 33--38 In this paper, we examine existing direct 3D ray-triangle intersection tests (i.e., those that do not first do a ray-plane test followed by a 2D test) for ray tracing triangles and show how the majority of them are mathematically equivalent. We then use these equivalencies to attempt faster intersection tests for single rays, ray packets with common origins, and general ray packets. We use two approaches, the first of which counts operations, and the second of which uses benchmarking on various processors as the fitness function of an optimization procedure. Finally, the operation-counting method is used to further optimize the code produced via the fitness function. Physically-Based Realistic Fire Rendering Vincent Pegoraro, Steven G. Parker Proceedings of the 2nd Eurographics Workshop on Natural Phenomena, pp. 51-59, 2006 Accurately rendering fires is a challenging problem due to the various subtle ways in which the electromagnetic waves interact with this complex participating medium. We present a new method for physically-based rendering of flames from detailed simulations of flame dynamics which accounts for their unique characteristics. Instead of relying on ad-hoc models, we build on fundamental molecular physics to compute the spectrally dependent absorption, emission and scattering properties of the various chemical compounds found in the fire. Combined with a model of the refractive process, and with tone-mapping techniques simulating the visual adaptation of a human observer, we are able to generate highly realistic renderings of various types of flames, including colorful flames containing chemical species with very characteristic spectral properties. From “Interactive Isosurface Ray Tracing of Large Octree Volumes” From “Ray Tracing Deformable Scenes using Dynamic Bounding Volume Hierarchies” From “Ray Tracing Animated Scenes using Coherent Grid Traversal” From “Ray Tracing Animated Scenes using Coherent Grid Traversal” From “Design for Parallel Interactive Ray Tracing Systems.” From “Optimizing Ray-Triangle Intersection via Automated Search” From “Physically-Based Realistic Fire Rendering” Boeing 777 Data courtesy of the Boeing Company. Rendered in Manta Interactive Ray Tracer