11. Materials

Scenes would be pretty boring if the surface every object had the same basic appearance. The easiest way to change the appearance of objects is with a Material node.

Most of the fields for this class are devoted to controlling colour in various ways. Colour is specified as triple like "0.0 0.4 0.8" that reflects the amount of red, green, and blue (respectively) to mix to product the colour. A value of 0.0 means don't use any of that primary colour, while a value of 1.0 means that you want 100% saturation of that primary colour. Creating colours is almost an art form in itself. The simplest approach for beginners is to start with the ambientColor field to specify the colour of an object, but once you are used to this go on to experiment with the other fields to see how they modify the results. Sometimes the difference is only apparent with different lighting situations.

The fields and respective default values are:

    Material {
        ambientColor   0.2 0.2 0.2
        diffuseColor   0.8 0.8 0.8
        specularColor  0 0 0
        emissiveColor  0 0 0
        shininess      0.2
        transparency   0
    }

Examples

Here is a Material node that would colour objects a pure blue:

    Material {
        ambientColor   0.0 0.0 1.0
    }

This example would result in a transparent, relatively shiny greenish colour, possibly for use with colouring an object made out of glass:

    Material {
        ambientColor   0.0 0.4 0.1
	shininess      0.5
        transparency   0.7
    }

More Information

Some information about materials in Open Inventor is available in chapter 3 of Inventor Mentor. More complex ways of changing appearance with textures are discussed in chapter 7.