> Thomas Auinger wrote:
>
>I noticed on my machine a crappy look of Sphere objects when
>their shininess is set to something below 10 (with 1.0 being
>the worst case) and lit by directional light. The edge between
>lit and dark part is sort of jugged, looks sort of triangulated?!!!
What you are seeing is called "saturation". It happens when the ambient,
diffuse and specular contributions to the lighting add up to more than one
(that is, brighter than pure white). In this case, OpenGL clamps the color
values which are greater than 1.0 to 1.0.
The saturation is happening because you have set the surface shininess to such
a small value. The "shininess" is an expression of how wide an angle light
is scattered off the surface. Shiny objects (like a mirror) reflect light
with very small amount of scattering and have a high shininess, less shiny
objects (like an orange) scatter refelcted light more, giving a "softer"
reflection. A value of 1.0 is very low, leading to all of the verticies which
are front facing to get the maximum specular color.
You need to adjust the shininess and the specular color together. Objects which
have a "soft" shininess also have a decreased amount of specular color as
well. Decreasing the shininess needs to be accompanied by decreasing the
intensity of the specular color. For example, a painted surface can have a
high gloss (high shininess, high specular intensity), semi-gloss (medium
shininess, medium specular intensity) or flat (no shininess, no specular
intensity).
A good graphics textbook should have more examples of how these factors
work together.
Doug Gehringer
Sun Microsystems
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