1. Parallel Spectral Renderer
Computer Systems Lab Presentation
Stuart Maier

2. Abstract
Computer generation of highly realistic images has been a difficult problem. Although there are algorithms that can generate images that look essentially real, they take large amounts of time to render. This project explores ways of distributing that onto multiple computers, in order to speed up the process.

3. Graphics Background Many different algorithms
Most unrealistic
Real-life based algorithms developed
Ray tracing
Path tracing
Spectral rendering

4. Ray Tracing Rays shoot through screen Rays seek light sources
Phong shading
Image from Wikipedia.

5. Path Tracing Rays don't seek light Rays can: Probabilistic Find light
Be absorbed
Be reflected
Be transmitted
Probabilistic

6. Spectral Rendering Complete color space RGB part illuminated
Many different colors can create the same RGB value
Image from Wikipedia.

7. Parallel Background BOINC Splitting data Multiple independent clients
No interclient communication
Clients barely talk with server
Splitting data
Pixels are divided up among clients

8. Design Written in C with MPI and OpenGL libraries
Currently implements a parallel spectral renderer with spectral colors
Six components
Main
Renderer
Object
Spectrum
Vector
XML

9. Main Runs the entire show Talks with MPI and OpenGL
Starts up the renderer
Passes off to the Renderer component

10. Renderer Holds information about the scene Renders the scene
Performs the high-level ray calculations

11. Object
Information about objects
Calculates ray-object intersections

12. Spectrum Contains the spectral colors Can retrieve these colors
Converts spectral colors to RGB ones for display

13. Vector Generic library Creates 3-D vectors and processes them
Used for spatial calculations

14. XML First component called after Main Reads in the scene file
Passes off information to Renderer

15. data.xml
<scene sampling="10" depth="4" width="256" height="256">
<camera x="0.0" y="0.0" z="0.0" />
<screen>
<origin x="-1.0" y="-1.0" z="1.0" />
<width x="2.0" y="0.0" z="0.0" />
<height x="0.0" y="2.0" z="0.0" />
</screen>
<object type="sphere" radius="0.2" index_refraction="1.5">
<origin x="0.0" y="0.0" z="1.0" />
<emmitivity color="black" />
<diffuse color="black" />
<reflectivity color="black" />
<refractivity color="white" />
</object>

16. Results

17. Analysis Spectral Renderer works in parallel No Cornell Box yet Grainy
Large amount of work

18. Cornell Box
Reference scene
Spectral colors
Not tested yet

19. Parallel Speedup Some speedup on multiple computers
Unequal work distribution
Network lag

20. Questions?