In the 3D display 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) 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.
Itotal = Ke C ;emissive
+ Ia Ka C ;ambient
+ Sum(i) [ ( NdotVi ) Ii Kd C ] ;diffuse
+ Sum(i) [ ( NdotSi )^ns Ii Ks ] ;specular
Where Itotal is the total intensity as an RGB triplet at any point on an object;
Ia is the intensity (RGB triplet) of the ambient light source (1.0 for the simple light model used in SHAPE);
Ii is the incident intensity (RGB triplet) at the object of directional or positional light source i (1.0 for the simple light model used in SHAPE);
C is the assigned color (RGB triplet) of the object (crystal edge, crystal face, symmetry axis or mirror plane color);
Ke is the emissive material coefficient of the object (Material Parameters dialog);
Ka is the ambient material coefficient of the object (Material Parameters dialog);
Ks is the specular material coefficient of the object (Material Parameters dialog);
ns is the specular exponent or shininess coefficient of the object (Material Parameters dialog);
N (a vector) is the normal to the surface at the point in question;
Vi (a vector) is the direction of the incident directional or positional light i at the point;
S (a vector) is the bisector of the angle between the light-surface vector (or Vi) and the eye-surface vector;
"dot" signifies the vector dot product.
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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 the Standard display mode.
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 Specular material 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 SHAPE, 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). For directional lights, specular reflection may not work well for polyhedra because faces at certain angles will give a solid white appearance.
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.
This equation ignores translucency, which causes colors objects lying at different depths to be blended.