When defining materials for your models, settings in the Material Editor dialog let you define how the surfaces react with light in the scene. In order to use correctly the various material settings, it is important to understand how they affect the interaction of light rays with objects in your models. The diagram below shows the various possibilities when a light ray strikes an object.

Legend:

• 1 — Light source
• 2 — Diffuse (percentage of light that is randomly dispersed in all directions).
• 3 — Specular (percentage of light reflected in the mirror direction) and Reflect (percentage of light that is visible in the mirror direction).
• 4 — Surface Normal
• 5 — Refract (angle that light "bends" as it passes through an object).
• 6 — Translucent (percentage of light that passes through an object and then is dispersed randomly in all directions on the back side of the object).
• 7 — Transparent (percentage of light that passes through the object).
• 8 — Finish (roughness of the surface, which controls the falloff of highlight on a surface).

In reality, all objects absorb some amount of light. That is, not all the light that strikes an object is reflected or transmitted. Similarly, when you define materials in your models, they should not be greater than 100% efficient. This is important, in particular, for materials that are to be used in photo-realistic images. For these materials, the following formula should be used:

Efficiency = Diffuse + Translucency + Specular + (100 - Opacity) <= 100

Using the Efficiency lock, in the Material Editor's advanced mode, you can select an Efficiency value, which is maintained as you modify the above settings. That is, if you modify a setting for Diffuse, Translucency, Specular, or Opacity, changes are made also to the remaining three settings to maintain the Efficiency setting.