In article <398EA5FD.F40F2F5C@xlstudio.com>, gemelli david 
<d.g### [at] xlstudiocom> wrote:

> This week-end, I tried MegaPOV radiosity and reflection blur.
> I made a scene with no light source and only one object with ambient
> (the white 'sky sphere' has ambient 1, anything else has ambient 0).

A white sky with ambient 1 seems pretty bright...unless you are trying 
to get a completely overcast sky. I would try using a pattern to make 
part of the sky much brighter than the rest(like a sun).


> Some questions:
> - what are the finish features that only interacts with 'true' light ? I
> tried metallic but I didn't see any difference.

All finish features interact with radiosity. The "metallic" modifier 
only affects the color of highlights though...it isn't surprising you 
didn't see a difference. The diffuse keyword affects the amount 
lighting(both radiosity and direct, from light sources) affects the 
color. Ambient affects the amount of light inherently in the 
texture...if you are using radiosity, this should be 0 for non-glowing 
objects. In MegaPOV, reflect_metallic makes reflections take on the 
color of the surface, this is more realistic than the default 
reflection. This could greatly affect some scenes, but others might show 
little difference.


> - when using low quality rendering, the brightness is false (lower than
> the high quality one) must I change brightness to correct it ? what
> radiosity parameter is involved ? I'm using:

As mentioned, this is because of the higher recursion. High recursion 
levels give more realistic results...but the extra bounces could make 
your scene a different brightness than you expected.
I don't understand the parameters very well yet, though. You might try 
using a white background or sky_sphere instead of a sphere...I think 
part of it might be additional radiosity samples brightening the sky. 
Since the sky is an object, radiosity is calculated for it...and most of 
those samples will hit the sky. Setting the "diffuse" of the sky to 0 
might also help.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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