Parallel Ray Tracer

Computer Systems Lab PresentationStuart 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