Renderman “Real-Time” Compositing

Real-Time Compositing Pipeline in PRMan Click Here for my Results

As a game development major, I’m keenly interested in finding ways of converting my knowledge of RSL to real-time. At SIGGRAPH 2006, Hal Bertram taught a session within the RenderMan for Everyone course called Produciton Rendering Acceleration Techniques. In this course, he outlined the fact that you can split renders into passes in RSL and simply add them together for the final render. This technique along with scalar multipliers and Bertram’s own Interaction Toolset enables the shader writer to render a scene in passes and tweak it in real-time. This can drastically streamlines the rendering process.

For my final project, I inted to work with Bertram’s toolset to create both image-based and geometry-based composites. This means that I will not only be working with camera shots from RIBs, but I’ll also be cacheing point and color data in order to tweak the camera angle in real-time.

In this way, I hope to create a fast, relatively simple pipeline for setting up lights and tweaking lighting conditions in RSL. I’d also like to cut down the amount of renders for a finalized image.

Some examples of Bertram’s Interaction Tools in use:

A basic visual flow for my proposed pipeline:

My steps for this project are as follows:

1) Set-up AOVs to be sent to Interaction Tools
2) Modify RIBs to send parameters to Interaction Tools
3) Generate an Image-Based Composite for tweaking lighting
4) Set-up geometry to cache points and color values
5) Generate a Geometry-Based Composite for tweaking lighting and camera position

Possible Additional Goals:

6) Generate occlusion in the pipeline to tweak samples in real-time
7) Test volumetrics in the pipeline for light fog

Possible Roadblocks:

- As of now, Interaction Tools is only compatible with versions of Linux. There is a Windows version in the works, but not planned for release any time soon. This means I’ll be attempting to use the Ubuntu machines from the school for this entire project.

- Interaction Tools works with PRMan 12.5 and 13.0, but the surface attributes meshes (SAM) don’t work with 13.0, yet. This means I may need to re-structure my goals as it pertains to Geometry-Based Compositing