David Kirk McAllister

OptiX: a general purpose ray tracing engine

The NVIDIA® OptiX™ ray tracing engine is a programmable system designed for NVIDIA GPUs and other highly parallel architectures. The OptiX engine builds on the key observation that most ray tracing algorithms can be implemented using a small set of programmable operations. Consequently, the core of OptiX is a domain-specific just-in-time compiler that generates custom ray tracing kernels by combining user-supplied programs for ray generation, material shading, object intersection, and scene traversal. This enables the implementation of a highly diverse set of ray tracing-based algorithms and applications, including interactive rendering, offline rendering, collision detection systems, artificial intelligence queries, and scientific simulations such as sound propagation. OptiX achieves high performance through a compact object model and application of several ray tracing-specific compiler optimizations. For ease of use it exposes a single-ray programming model with full support for recursion and a dynamic dispatch mechanism similar to virtual function calls.

Simpler and faster HLBVH with work queues

A recently developed algorithm called Hierachical Linear Bounding Volume Hierarchies (HLBVH) has demonstrated the feasibility of reconstructing the spatial index needed for ray tracing in real-time, even in the presence of millions of fully dynamic triangles. In this work we present a simpler and faster variant of HLBVH, where all the complex book-keeping of prefix sums, compaction and partial breadth-first tree traversal needed for spatial partitioning has been replaced with an elegant pipeline built on top of efficient work queues and binary search. The new algorithm is both faster and more memory efficient, removing the need for temporary storage of geometry data for intermediate computations. Finally, the same pipeline has been extended to parallelize the construction of the top-level SAH optimized tree on the GPU, eliminating round-trips to the CPU, accelerating the overall construction speed by a factor of 5 to 10x.

GPU ray tracing

The NVIDIA® OptiX#8482; ray tracing engine is a programmable system designed for NVIDIA GPUs and other highly parallel architectures. The OptiX engine builds on the key observation that most ray tracing algorithms can be implemented using a small set of programmable operations. Consequently, the core of OptiX is a domain-specific just-in-time compiler that generates custom ray tracing kernels by combining user-supplied programs for ray generation, material shading, object intersection, and scene traversal. This enables the implementation of a highly diverse set of ray tracing-based algorithms and applications, including interactive rendering, offline rendering, collision detection systems, artificial intelligence queries, and scientific simulations such as sound propagation. OptiX achieves high performance through a compact object model and application of several ray tracing-specific compiler optimizations. For ease of use it exposes a single-ray programming model with full support for recursion and a dynamic dispatch mechanism similar to virtual function calls.

Measuring and Rendering Spatially-Varying Fabrics

Most surfaces, including most fabrics, have different reflectance at different points on the surface. The reflectance also varies based on the incident and exitant light directions. This spatially and angularly varying surface appearance is a 6D function, sometimes called the Spatial Bi-directional Reflectance Distribution Function (SBRDF). We present a system for measuring the SBRDF of real fabrics in a lab setting. Our system is able to capture distinct anisotropic BRDFs at each point on the fabric. The measurement device yields from 300 MB to 8 GB of reflectance data for complex fabrics. We compress the SBRDF using a sum of very few nonlinear bases suited to BRDFs, yielding a highly compact texture map of from 2 to 20 MB, suitable for accurately visualizing articles made of specific fabrics interactively using commodity graphics hardware. We provide an online database of sampled SBRDFs, both in raw form and as final texture maps.