Dialog Box - called from: Input2 Menu
In the 3D drawing mode the material properties of objects determine the way the objects interact with the light sources.
The color observed at a given point is a resultant of the light source(s) (3D Lighting) and the material properties; that is, the RGB coefficients of the Ambient, Diffuse and Specular components of the light source(s) are multiplied by the specified colors of the objects, and by the material coefficients in this dialog, then the results are limited to the range 0.0-1.0. See Lighting Equation for details.
Ambient light has no direction or origin and is considered to bathe all objects uniformly. Having a significant ambient component causes non-illuminated parts of objects to be other than black. It thus "softens" the illumination in a somewhat similar way to the Darkest Shade and Darkness Angle parameters (Shading dialog) in 2D Drawing modes. Note that there must be a separate ambient light to show this component.
Diffuse color is usually the main component of the appearance of objects. The intensity of the color is dependent on the angle between the light ray and the normal to the surface in question.
Specular reflection only occurs when the normal to the surface in question is close to bisecting the angle between the incident light and the vector from the point on the surface to the eye. It produces bright highlights on a curved surface. The larger the
Shininess coefficient, the smaller will be the bright specular highlight on a curved surface. The shininess coefficient has a maximum of 128 because of computational restrictions, but values on the order of 5-30 are usually realistic.
In ATOMS, specular reflection is always white, that is it does not depend on the color of the object, only the color of the light source(s). Specular reflection does not work well for polyhedra because faces at the reflection angle will give an essentially solid white appearance, rather than a bright spot. This is because the angle is calculated for the corners of the face, and interpolated for each point in the interior of the face.
When thermal ellipsoids are shown in 3D Drawing modes (see Ellipsoid Parameters), the material parameters used for both the cutout octant and the principal-plane bands are those for polyhedra - this is to avoid distracting specular reflections from large flat surfaces.
Emission is similar to ambient, except that there is no dependence on the color of any light source. A high value of emission makes an object look like is is glowing.