Manuka: A Batch-Shading Architecture for Spectral Path Tracing in Movie Production

The Manuka rendering architecture has been designed in the spirit of the classic REYES rendering architecture: to enable the creation of visually rich computer generated imagery for visual effects in movie production. Following in the footsteps of REYES over the past 30 years, this means supporting extremely complex geometry, texturing, and shading. In the current generation of renderers, it is essential to support very accurate global illumination as a means to naturally tie together different assets in a picture. This is commonly achieved with Monte Carlo path tracing, using a paradigm often called shade on hit, in which the renderer alternates tracing rays with running shaders on the various ray hits. The shaders take the role of generating the inputs of the local material structure, which is then used by path-sampling logic to evaluate contributions and to inform what further rays to cast through the scene. We propose a shade before hit paradigm instead and minimise I/O strain on the system, leveraging locality of reference by running pattern generation shaders before we execute light transport simulation by path sampling. We describe a full architecture built around this approach, featuring spectral light transport and a flexible implementation of multiple importance sampling (MIS), resulting in a system able to support a comparable amount of extensibility to what made the REYES rendering architecture successful over many decades.