Hello World ;)

i am trying to create a material that does NOT become bright on direct hit by
light source (but keeps its base color, e.g. 0.5,0.5,0.5). but it shall increase
its brightness when hit by light that has been reflected/refracted.

what i want is to render glass-like objects ontop of a light gray surface. but i
need the surface to keep its color and not show a pointlights phong-like
whiteish arua, instead it shall stay gray everywhere. (i guess the easiest way
is to set an ambient value and disable lighting for that material). but i still
want caustics or other refraction effects that cause (colored) light coming
through the glass objects to colorize this otherwise gray surface.

any ideas?

thanks for your help,
  daniel / sirleto

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> Hello World ;)
>
> i am trying to create a material that does NOT become bright on direct hit by
> light source (but keeps its base color, e.g. 0.5,0.5,0.5). but it shall increase
> its brightness when hit by light that has been reflected/refracted.
>
> what i want is to render glass-like objects ontop of a light gray surface. but i
> need the surface to keep its color and not show a pointlights phong-like
> whiteish arua, instead it shall stay gray everywhere. (i guess the easiest way
> is to set an ambient value and disable lighting for that material). but i still
> want caustics or other refraction effects that cause (colored) light coming
> through the glass objects to colorize this otherwise gray surface.
>
> any ideas?
>
> thanks for your help,
>    daniel / sirleto
>
>

If you want the illumination to be independent from the angle of 
incidence of light but still be affected by light_source, you can add 
brilliance 0 to the finish. Also, photons WILL show on that object and 
shadowed areas will be darker.

To have a surface that will always have the same brightness and don't 
display any shadow, use finish{ambient 1 diffuse 0}. In this case, 
photons will NOT show. diffuse 0 mean that the texture NEVER react to 
any illumination at all. For your case, it's _NOT_ a viable solution.

If you don't want to have any highlights, just don't set any phong or 
specular in the finish.

To have brightning from reflected and refracted light, you need to 
enable photons mapping.

Add:

photons{spacing 0.1} OR photons{count 1e6}

to your global_settings section. Those are starting values. In some 
cases, you can get by with smaller values, or need larger ones. I 
suggest using count if you only have 1 to 3 target objects and only one 
light_source. Use spacing when you have multiple light_source and 
several target objects.
Having several transparent objects lined up will lead to the loss of 
many photons. Only enable photons for the FIRST object in line. The 
secondary photons totaly ignore the photons block. They can get 
reflected even it the target object's photons block have reflection off...

Next, add:
photons{target reflection on refraction on} to the refractive and 
reflective objects.

Alternatively, you can use:
photons{target Spacing_Multiplier reflection on refraction on}

It's usefull if you have a problem object that need more photons but the 
rest of the scene renders OK. Also usefull for large, mostly featureless 
object, like a large flat mirror, that don't need as many photons as the 
rest. Use a value <1 to increase the number of photons shot at that 
object and >1 to reduce that number.

If you want your refracted light to show chromatic dispersion, add 
dispersion 1.01 in the interior. Adjust the value as needed.



Alain

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