BMRT: A Global Illumination Implementation of the RenderMan Standard

Abstract

The RenderMan Interface specification proposed by Pixar is a standard for communication between modeling software and rendering software or devices. This standard has proven very powerful and is extremely popular in production work. Although the standard itself claims not to specify a rendering algorithm, people have speculated RenderMan and global illumination are mutually incompatible.We have implemented a rendering system which fully adheres to the RenderMan Interface and uses global illumination algorithms.Specifically, this implementation supports progressive refinement radiosity and distribution ray tracing in a two-pass approach. This rendering system is widely distributed, very popular, and has been used in production (three properties usually not found in global illumination renderers). We discuss how we overcame problems in mating global illumination algorithms with the RenderMan standard, and make recommendations for future versions of the standard to better accommodate such algorithms. We also present a summary of important lessons we learned by creating and distributing this tool.

The design of a texture mapping unit with effective MIP-map level selection for real-time ray tracing

“…We also implement the proposed architecture by integrating it into the existing ray tracing hardware in [5]. Experimental results show our approach significantly reduces the computation requirements compared to [2].…”

“…Ray differential-based techniques have been provided in [2,3] to select the proper MIP-map level for production (off-line) renderers, such as Pixar's RenderMan. A ray differential is defined as the difference between a ray and its neighboring rays [3].…”

“…Similar to the rasterization algorithm, BMRT [2] determine du and dv by calculating the projection of texture coordinates onto the image plane. Suppose P l is the total distance from the camera position to the sample point P , d s is the distance between screen space samples, and d est is the world space distance between screen samples at point P .…”

“…In [1], various practical methods for MIP-map level selection were investigated within the context of the rasterization technique used in OpenGL. Several MIP-map level selection methods using a ray tracing algorithm and based on the ray differential have been proposed in [2,3]. These were developed for production (off-line) renderers, such as Pixar's RenderMan [4].…”

Direct Ray Tracing of Displacement Mapped Triangles

“…Somewhat surprisingly, displacement maps are almost never used in ray tracing. This turns out to be for entirely technical reasons; a straightforward implementation would need to store more micropolygons than would fit in main memory on most computers [4]. For this reason, sophisticated caching strategies have been suggested [12].…”