Am 03.08.2015 um 19:10 schrieb Alain:

>>   finish {
>>     diffuse 0.9
>>        ambient 0.4
>>        specular 1.0
>>        roughness 0.1
>>        brilliance 0.01
>>        reflection {
>>         0.3
>>            }
>
> The summ of diffuse, ambient and reflection should stay under 1.
> Otherwise, the object return more light than it receive.

Actually ambient is outside of this equation. The choice of this setting 
should be based on...:

- The diffuse value (if you increase diffuse, you should also increase 
ambient)

- The brightness and geometry of surrounding objects (if they're plain 
white and oriented straight towards the object in question, ambient 
should equal diffuse)

The above is true for brilliance 1.0, or if the "albedo" keyword is used 
with diffuse.


As for the sum of diffuse and reflection, the rule that it should stay 
under 1 is only true when...:

- The reflection is constant (as is the case here), AND

- brilliance is 1.0, or the "albedo" keyword is used with diffuse.


The most realistic results can be obtained by using:

     #version 3.71; // !!!
     texture {
       finish {
         ambient A*D
         diffuse albedo D
         brilliance 1.0
         specular albedo R
         fresnel on // this is what you'll need 3.7.1 for
         reflection { R fresnel on }
       }
     }
     interior {
       ior I
     }

with D <= 1.0, R <= 1.0, and A depending on surrounding materials and 
geometry (better yet, use radiosity); no other constraints apply, as the 
"fresnel on" in the finish block itself and in the reflection block will 
make sure that the diffuse is properly balanced with the reflection.

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