RTSL Ward Scene RTSL: a Ray Tracing Shading Language
Steven G. Parker, Solomon Boulos, James Bigler, and Austin Robinson.
To appear IEEE Symposium on Interactive Ray Tracing 2007

We present a new domain-specific programming language suitable for extending both interactive and non-interactive ray tracing systems. This language, called ``ray tracing shading language'' (RTSL), builds on the GLSL language that is a part of the OpenGL specification and familiar to GPU programmers. This language allows a programmer to implement new cameras, primitives, textures, lights, and materials that can be used in multiple rendering systems. RTSL presents a single-ray interface that is easy to program for novice programmers. Through an advanced compiler, packet-based SIMD-optimized code can be generated that is performance competitive with hand-optimized code.
 
Pulli Edit Interactive Editing and Modeling of Bidirectional Texture Functions
Jan Kautz, Solomon Boulos, and Fredo Durand.
To appear SIGGRAPH 2007
Video (DivX 6)

Bidirectional texture functions (BTFs) extend the notion of a texture to have both lighting and view variations. While a few groups have captured a handful of high quality measured BTFs, content creators had no way to get a red wool sweater from the blue one provided. In this paper, we describe the editing operations we implemented inside of BTFShop: an interactive BTF editing system.
 
Conference Scene (DRT) Packet-based Whitted and Distribution Ray Tracing
Solomon Boulos, David Edwards, J. Dylan Lacewell, Joe Kniss, Jan Kautz, Ingo Wald and Peter Shirley
Proceedings of Graphics Interface 2007
BibTeX | Presentation (PDF)

Much progress has been made toward interactive ray tracing, but most research has focused specifically on ray casting. A common approach is to use "packets" of rays to amortize cost across sets of rays. Whether "packets" can be used to speed up the cost of reflection and refraction rays is unclear. The issue is complicated since such rays do not share common origins and often have less directional coherence than viewing and shadow rays. Since the primary advantage of ray tracing over rasterization is the computation of global effects, such as accurate reflection and refraction, this lack of knowledge should be corrected. We are also interested in exploring whether distribution ray tracing, due to its stochastic properties, further erodes the effectiveness of techniques used to accelerate ray casting. This paper addresses the question of whether packet-based ray algorithms can be effectively used for more than visibility computation. We show that by choosing an appropriate data structure and a suitable packet assembly algorithm we can extend the idea of "packets" from ray casting to Whitted-style and distribution ray tracing, while maintaining efficiency.

Note: a previous version of this work is contained in a technical report (see below).
 
IA Example Geometric and Arithmetic Culling Methods for Entire Ray Packets
Solomon Boulos, Ingo Wald and Peter Shirley
Technical Report, School of Computing, University of Utah, No UUCS-06-10, 2006

Recent interactive ray tracing performance has been mainly derived from the use of ray packets. Larger ray packets allow for significant amortization of both computations and memory accesses; however, the majority of primitives are still intersected by each ray in a packet.

This paper discusses several methods to cull entire ray packets against common primitives (box, triangle, and sphere) that allows an arbitrary number of rays to be tested by a single test. This provides cheap ``all miss'' or ``all hit'' tests and may substantially improve the performance of an interactive ray tracer. The paper surveys current methods, provides details on three particular approaches using interval arithmetic, bounding planes, and corner rays, describes how the respective bounding primitives can be easily and efficiently constructed, and points out the relation among the different fundamental concepts.
 
Fairy Forest Interactive Distribution Ray Tracing
Solomon Boulos, David Edwards, J. Dylan Lacewell, Joe Kniss, Jan Kautz, Ingo Wald and Peter Shirley
Technical Report, SCI Institute, University of Utah, No UUSCI-2006-022, 2006
BibTeX | Movie | SIGGRAPH 2006 Course Presentation (PDF)

Current interactive ray tracing systems have focused on highly coherent sets of rays such as primary rays or rays shot to a single point light. In this work we investigate interactive distribution ray tracing in the spirit of Cook's original paper from 1984. Using the bounding volume hierarchy (BVH) from our previous work, we maintain interactivity while including effects such as depth of field, area light sources, motion blur, glossy reflection, refraction and volume rendering. We also demonstrate methods for stable sampling to avoid frame to frame scintillation or crawl and demonstrate how to avoid aliasing artifacts caused by repeated tiling of static sample patterns.
 
Fairy Forest Ray Tracing Deformable Scenes using Dynamic Bounding Volume Hierarchies
Ingo Wald, Solomon Boulos and Peter Shirley
ACM Transaction on Graphics, Volume 26, Issue 1, January 2007
BibTeX

Ray tracing systems have traditionally been limited to static walkthroughs. The reason for this is that the acceleration structures used to speed up ray-scene queries are usually computed as an expensive offline preprocess. This work demonstrates that a bounding volume hierarchy (BVH) can instead be updated per frame to handle animated scenes. BVH construction and traversal is also outlined, so that the BVH can be made competitive with previous best practices for interactive ray tracing.
 
Hogum Image Synthesis using Adjoint Photons
R. Keith Morley, Solomon Boulos, Jared Johnson, Dave Edwards, Peter Shirley, Michael Ashikhmin and Simon Premoze
Proceedings of Graphics Interface 2006
BibTeX | Presentation

Traditional rendering systems have incorporated several layers of hacks based on simple scenes such as the Cornell Box. Techniques built for the Cornell Box, however, do not easily apply to more complicated scenes such as the figure to the left which is computed using the measured radiance of the Sun as well as Rayleigh scattering to get the blue sky. The smoky cloud is from simulation data and would traditionally slow down a renderer considerably. In our system, we present an image synthesis algorithm based on tracing photons from sensors to light sources and demonstrate that this is physically valid and easier to motivate than Kajiya's path tracing algorithm.
 
Transparent Boeing 777 An Application of Scalable Massive Model Interaction using Shared-Memory Systems
Abe Stephens, Solomon Boulos, James Bigler, Ingo Wald, and Steven G. Parker
Proceedings of the 7th Eurographics Symposium on Parallel Graphics and Visualization, May 2006
Using the Manta Interactive Ray Tracer, we developed a complete digital mockup demo for the Boeing 777 dataset. The dataset consists of color coded 350 million polygons. To aid in visualization and interaction with the dataset we added transparent rendering, cutting planes, object hiding based on part serial numbers and ambient occlusion. Using a large shared-memory system, we were able to achieve interactive performance for this demo at both SIGGRAPH 2005 and Supercomputing 2005.
 
Anisotropic Spheres The Halfway Vector Disk for BRDF Modeling
Dave Edwards, Solomon Boulos, Jared Johnson, Peter Shirley, Michael Ashkikhmin, Michael Stark and Chris Wyman
ACM Transactions on Graphics Volume 25 Issue 1, Jan 2006

This work sought to investigate energy conserving models of reflectance for computer graphics. We developed a new set of parameterizations based on a halfway vector disk, which allows us to ensure energy conservation. While our new model is not able to ensure reciprocity, we are able to fit measured data with very few coefficients (colors and exponents).

 
Lucy image Memory Sharing for Interactive Ray Tracing on Clusters
David E. DeMarle, Christiaan P. Gribble, Solomon Boulos and Steven G. Parker
Parallel Computing, Vol. 31, No. 2, pp. 221--242. 2005.

In this paper, we describe some techniques we used to reduce the number of cache misses in our distributed interactive ray tracer (dirt). Because the system is distributed over a cluster of workstations using a gigabit interconnect, the cost of a cache miss is nearly 600 milliseconds. By reordering geometric data, such as the Lucy model from Stanford, we were able to reduce cache misses by more than a factor of two when local memory available was low.