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Blog by Ina Centaur » materials

 

Theory of Light in CG, Part I

Written by ina on Monday, 21 of January , 2008 at 4:29 am
Tags: , , , , ,

A while ago, I promised someone to write a brief intro to some technical CG terms used in materials such as specular and diffuse amount. I guess that’s what I’m doing now!

Light rays do not exist, per se, in pixels — and, incidentally, hence the bane of digital cameras vs. traditional cameras, btw — but, it’s interesting to note that 3d software are often developed based on the physical theory of light. Raytracing is basically about light bouncing off things and onto other things so that the colors appear the right shade.

When light hits a surface, it is either reflected or transmitted (or absorbed - but, in general, we needn’t worry about that in CG).

So, I really like how modo breaks up its material panels into ref and tran:

Reflective

  • Diffuse Color: The object’s basic color. If pure white light hits the object, this would be the color you see. Diffuse Amount would modulate the intensity. A Diffuse Amount of 0 yields the best version of a black body your screen can represent.
  • Specular Color: The object’s highlights. A Specular Amount of 0 would yield a dull un-shiny object. Specular should be equal to Reflection for realistic effects.
    • Specular Fresnel: Fresnel, in this case, basically refers to specular light hitting an object perpendicularly. A 100% specular fresnel would mean an object’s reflection perpendicular to you becomes unrealistically white. It’s named after this guy named Fresnel who proposed that waves basically sprout out perpendicularly from points.
  • Reflection: 100% turns your object into a mirror. This actually doesn’t have a real world analogy.

Transmissive

Category: Tutorials

Who is Ina Centaur?

A 25-year old American polymath of Taiwanese ancestry pretending to be old and Caucasian in Second Life. Semi-retired independent scholar also dabbling as an independent artist in new media, particularly theatre and the humanities—notably Shakespeare. Programmer, playwright and novelist. Formal academic background in http://portfolio.inacentaur.com/ina/scientist, philosophy, and bioengineering.

This is largely a personal blog which isn't always up-to-date. There's no one definitive way to stalk me ;-).