This paper describes work in progress to develop a standard for interoperability ariiong high-petforniance scientific coniponents. This research sterns front growing recognition that the scientific coniniunity needs to better manage the coniplexity of ntultidisciplinuiy simulations and better address scalable petforniance issues on parallel and distributed architectures. Driving forces are the need for fast connections among components that perform numerically intensive work and for parallel collective interactions among cornponetits that use multiple processes or threads. This paper focuses on the areas we believe are niost crucial in this context, naiizely, an intetface definition language that supports scientipc abstractions for specifying coriiponent interfaces and a ports connection model for specifiing component interactions.

Ray tracing has long been a method of choice for off-line rendering, but traditionally was too slow for interactive use. With faster hardware and algorithmic improvements this has recently changed, and real-time ray tracing is finally within reach. However, real-time capability also opens up new problems that do not exist in an off-line environment. In particular real-time ray tracing offers the opportunity to interactively ray trace moving/animated scene content. This presents a challenge to the data structures that have been developed for ray tracing over the past few decades. Spatial data structures crucial for fast ray tracing must be rebuilt or updated as the scene changes, and this can become a bottleneck for the speed of ray tracing. This bottleneck has recently received much attention by researchers and that has resulted in a multitude of different algorithms, data structures and strategies for handling animated scenes. The effectiveness of techniques for ray tracing dynamic scenes vary dramatically depending on details such as scene complexity, model structure, type of motion and the coherency of the rays. Consequently, there is so far no approach that is best in all cases, and determining the best technique for a particular problem can be a challenge. In this State of the Art Report (STAR), we aim to survey the different approaches to ray tracing animated scenes, discussing their strengths and weaknesses, and their relationship to other approaches. The overall goal is to help the reader choose the best approach depending on the situation, and to expose promising areas where there is potential for algorithmic improvements.

Abstract.Interactive rendering requires rapid visual feedback. The render cache is a new method for achieving this when using high-quality pixel-oriented renderers such as ray tracing that are usually considered too slow for interactive use. The render cache provides visual feedback at a rate faster than the renderer can generate complete frames, at the cost of producing approximate images during camera and object motion. The method works both by caching previous results and reprojecting them to estimate the current image and by directing the renderer's sampling to more rapidly improve subsequent images. Our implementation demonstrates an interactive application working with both ray tracing and path tracing renderers in situations where they would normally be considered too expensive. Moreover we accomplish this using a software only implementation without the use of 3D graphics hardware.

Figure 1: Several animated models ray traced using our coherent grid traversal: a) A gesturing hand of 16K triangles. b) An animated "Poser" model (78K triangles). c) Animated wind-up toys (11K triangles) walking and jumping incoherently around each other. d) A rigid-body dynamics simulation of marbles (8.8K triangles). e) A complex scene of 174K animated triangles, where a fairy and a dragonfly dance through an animated forest. Scenes are rebuilt from scratch every frame, allowing fully dynamic animation. Including shading, texturing, and hard shadows, as used in the above images, we can render these scenes at 1024 × 1024 pixels with 15.3, 7.8, 10.2, 26.2, and 1.4 frames per second on a dual 3.2 GHz Xeon. Excluding shading, texturing, and shadows, we achieve 34.5, 15.8, 29.3, 57.1, and 3.4 frames per second. AbstractWe present a new approach to interactive ray tracing of moderatesized 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.

The Common Component Architecture (CCA) provides a means for software developers to manage the complexity of large-scale scientific simulations and to move toward a plug-and-play environment for high-performance computing. In the scientific computing context, component models also promote collaboration using independently developed software, thereby allowing particular individuals or groups to focus on the aspects of greatest interest to them. The CCA supports parallel and distributed computing as well as local high-performance connections between components in a language-independent manner. The design places minimal requirements on components and thus facilitates the integration of existing code into the CCA environment. The CCA model imposes minimal overhead to minimize the impact on application performance. The focus on high performance distinguishes the CCA from most other component models. The CCA is being applied within an increasing range of disciplines, including combustion research, global climate simulation, and computational chemistry.

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We examine a rendering system that interactively ray traces an image on a conventional multiprocessor. The implementation is "brute force" in that it explicitly traces rays through every screen pixel, yet pays careful attention to system resources for acceleration. The design of the system is described, along with issues related to material models, lighting and shadows, and frameless rendering. The system is demonstrated for several different types of input scenes.

Figure 1: Large volume data ray-traced at 512 2 using octrees for compression and acceleration. From left to right: (1) LLNL Richtmyer-Meshkov instability field (shown at timestep 270, with an isovalue of 100). (2) Closer view of the previous scene. (3) Utah CSAFE heptane simulation (timestep 152, isovalue 42). Data is losslessly compressed into an octree volume to occupy less than one quarter the size of the original 3D array. Our approach permits storage of large data such as the LLNL simulation, and full sequences of medium-size data such as the heptane, in main memory of consumer machines. Frame rates on an Intel Core Duo 2.16 GHz laptop with 2 GB RAM are 2.4, 1.3, and 3.3 fps respectively. On a 16-node NUMA 2.4 GHz Opteron workstation, these images render at 17.9, 9.8, and 22.0 fps. ABSTRACTWe present a technique for ray tracing isosurfaces of large compressed structured volumes. Data is first converted into a losslesscompression octree representation that occupies a fraction of the original memory footprint. An isosurface is then dynamically rendered 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 architectures, and render large time-variant data that could not otherwise be accomodated.