Parallel Ray Tracer Computer Systems Lab Presentation Stuart Maier

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.

Graphics Background Many different algorithms  Most unrealistic Real-life based algorithms developed Ray tracing most important  Shoots rays from camera  Interact with intersected objects  Local illumination

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

Phong shading Formula for calculating light

Graphics cont. Photon mapping  Two pass algorithm  Creates photon map  Ray tracing afterwards  Biased  Still not realistic enough

Graphics cont. Path tracing  Rays don't seek light  Rays can: Find light Be absorbed Be transmitted Spectral rendering  Full spectrum of colors

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

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

Design Written in C with MPI and OpenGL libraries Currently implements a parallel ray tracer with Phong shading Five components  Main  Renderer  Object  Vector  XML

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

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

Object Information about objects Calculates ray-object intersections

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

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