CGNetworks Feature :: 3D Rendering History
Part 2: To Photorealism and Beyond.
By: Dmitry Shklyar :: Page 1 | Page 2 | Page 3
Date: Wednesday, 22 October 2003

Introduction
With our first installment of 3D Rendering History, CGNetworks delivered a glimpse into the industries rendering past to gain some insight to where the actual technologies derived from. The second installment, To Photorealism and Beyond, delves even deeper to where rendering technologies currently sit, what they offer and where it may lead to in the coming years.

Since the 1960's, obtaining renders which were indistinguishable from photographs has been a much sought after goal, the Holy Grail of 3D if you will. Over the years, many difficulties have arisen to achieve photorealism, which leads us to one of the larger issues in current CG technology, global illumination. Global illumination (GI) refers to any physical based simulation of light being scattered in an artificial environment.

The search for Global Illumination
To clarify, GI is not an algorithm, instead, it is an effect achieved by many. The first algorithm, devised to tackle this problem was ray tracing. Yes, you read it correctly, ray tracing was initially thought of as a method to calculate GI. The very first computer based implementation of ray tracing was performed at IBM in 1968 by a researcher named Appel where he published a paper entitled Some Techniques for Shading Machine Renderings of Solids. Being that it was 1968, computers were nowhere near being capable of practically utilizing this algorithm.

It wasn't until 1980 when Turner Whitted published his groundbreaking paper entitled An Improved Illumination Model for Shaded Display. Whitted's paper described a ray tracing algorithm which facilitated for shadows, reflections, and refractions. Whitted's method was so simple that it could be described in as few as 3 functions, comprising of about a dozen lines of pseudo code [2]. Because of these reasons, most of today's commercial rendering packages are based on Turner Whitted's research [1].

Ray Tracing
Ray tracing works by shooting a ray from the viewer's eye into the scene, where it either leaves that scene or hits another object. If a ray meets an object, it then sends a secondary ray in the direction of the surface normal, until it either hits another surface, in which case the object is in shadow, or until it hits a light. If a surface is transparent, a ray is transmitted through that object in a direction which is determined in part of that object's index of refraction.

ray tracing

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