The sum of all three ought to add up to 1. Basically, you want all of the light coming off a surface to add up to 100% or less of the light that hits it, unless the surface is glowing or something. Real life isn't quite that simple of course, so the rules aren't hard and fast, but the idea is that if you shine a light on a surface, some light may be scattered diffusely by the surface (that's the diffuse component), some may penetrate the surface and be bent by it (that's the refraction component) and some may be reflected coherently by the surface (that's the reflection component). Some light may be absorbed by the surface and converted to heat (effectively that's light that gets lost). When you add up all those different amounts of light, the sum shouldn't be more than the amount of light you shone on the surface in the first place, so the components should add up to 1, or less than 1 if some of the light is being absorbed. If you use ambience as a sort of fake global illumination effect (to light up areas that aren't directly hit by light, as though they were being hit by scattered light from other objects in the scene), then you should include the ambient value in the sum as well and make sure the whole thing adds up to 1 or less. If you use ambience to create a glow effect, then it doesn't count toward the sum.

View Ajax's Gallery - View Ajax's Freestuff - View Ajax's Store - Send Ajax a message