# Ray Tracing

### Introduction

Ray Tracing is a global illumination based rendering method. It
traces rays of light from the eye back through the image plane into the scene. Then the
rays are tested against all objects in the scene to determine if they intersect any
objects. If the ray misses all objects, then that pixel is shaded the background color.
Ray tracing handles shadows, multiple specular reflections, and texture mapping in a very
easy straight-forward manner.

Note that ray tracing, like scan-line graphics, is a point sampling
algorithm. We sample a continuous image in world coordinates by shooting one or more rays
through each pixel. Like all point sampling algorithms, this leads to the potential
problem of aliasing, which is manifested in computer
graphics by jagged edges or other nasty visual artifacts.

In ray tracing, a ray of light is traced in a backwards direction.
That is, we start from the eye or camera and trace the ray through a pixel in the image
plane into the scene and determine what it hits. The pixel is then set to the color values
returned by the ray.

Overview of
Ray Tracing

Simple Global Illumination Model
for Ray Tracing

Computing a Reflected Ray

Ray-Object intersections

Practical considerations in writing
a Ray Tracer

Computational acceleration
techniques in ray tracing

Advanced Ray Tracing Techniques

A
Ray Tracing demonstration program

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Last changed July 20, 1999, G. Scott Owen, owen@siggraph.org