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Maxwell Render 2.5 User Manual

Chapter 10. Maxwell Materials | 52

10 MAXWELL MATERIALS

10.01 Maxwell Materials

Before explaining the material parameters used in the Maxwell material system, it is

important to have a basic understanding of what light is, how it interacts with materials

and why a material looks shiny, dull, transparent etc. Please review this information as it

will make the parameters in the Maxwell material editor much easier to understand.

What is light?

Visible light is really a very small portion in a range of electromagnetic radiation. This

radiation travels in waves of different wavelengths. The difference in wavelengths (the

“tops” of each wave) is what makes the difference between blue, red, gamma rays, x-rays,

radio waves etc.

“White light” is a combination of all the colors in the visible light spectrum. When we

perceive an object as red for example, what really happens is that white light falls on a

red surface, and all the wavelengths except those that give red light are absorbed by the

material. Only the red portion of the spectrum is reected back.

Diffuse – Specular & Reected light

We see an object because light is reected from its surface into our eyes. That is, ALL

light is reected light. This may sound confusing at rst because it has become common

in renderers to refer to reected light as specular (or sharply) reected light.

In the real world light does not have a separate “diffuse” or “specular” part. So what

makes a surface look dull, or mirror like? It is the smoothness of that surface.

A surface which is not very smooth has tiny imperfections which scatter the light in all

directions, thus creating a very “diffuse” reection of its environment. So it is the reection

of light from an uneven or granular surface, resulting in an incoming light wave being

reected at a number of angles.

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Arrow Group Industries LM86 Manual do Utilizador Página 52