Kenneth nous apporta ses lumieres en ce 09/08/2006 04:48:
> Hi, Alain, thanks for posting these tips. I do have some questions (of
> course!):
> 
> Alain <ele### [at] netscapenet> wrote:
> 
>> Default to 1. It's a multiplicator for the returned radiosity samples. Without
>> this, your scene would be almost all black.
> 
> For some not-yet-understandable reason (perhaps because the light_sphere is
> so small)  I HAD to pump the brightness up, otherwise the scene was just
> way too dark. But this surely interacts with other values, so perhaps it
> should be lowered, and some other things adjusted.
Increase the ambient value of the "light", you can also increase the RGB value 
beyong 1. You are not limited to values from 0 to 1.
> 
>> Shifting this "may" help you getting rid of some artefacts near corners like
>> dark spots along inside corners.
> 
> Shifting it up ot down?  Is it better to use a higher value for this or a
> lower value?
Equivalent. You only want the pretrace sampling to shift place so that they miss 
the problem pixels. It's also advisable to move the camera a very small amount, 
like +/-0.000001 unit.
> 
>> Lowering this may enable you to use more relaxed settings elswhere, possibly
>> lending to somewhat shorter render times.
> 
> I'll try that.  Lower values do produce a drastic difference in smoothing
> things out. But does a lower value also make subtle artifacts more visible
> and
> pronounced? It seems to, but my eyes may be playing tricks on me.
> 
>> This puts a cap on the brightness. Not importent in your case as you apparently
>> don't have any object with a brightness larger than 1.
> 
> I'm a bit fuzzy on this: Does it control the brightness of rays shot from
> the light source, or the brightness of BOUNCED rays? Or both?? I thought it
Both if you use a high ambient "light" in place of a regulat light_source.
> would keep any area of the scene from exceeding a certain brightness, but
> that doesn't seem so; I can easily "wash out" areas of the scene closest to
> the light sphere if I'm not careful. So, I don't really understand what
> max_sample does.
This "wash out" is due to oversaturation. It appens when the (incident light * 
brightness * diffuse) leads to RGB values greater than 1. Those values are taken 
"as is" during calculations, then clipped to 1 in the final image.
> 
>> 1/20 the default of 0.5.
> 
> Sorry, I don't understand that. Explain?
Half of 0.5 is 0.25. 1/20 if 0.5 is 0.025.
Your specified error_bound of 0.9 gets lowered to 0.0225 during the last 
pretrace step. That's prety small.
> 
>> Why? Default to "on". Only relevant if you do multi-pass or distributed render.
> 
> I've found that the quality gets better with it off--at least in this
> particular scene. It's a subtle difference, but it's there.
Good reason.
>> You may try lowering brightness to 1 and bump up the pigment or ambient of the
>> small ambient light sphere.
> 
> Yes, that does help. I'll work with the idea.
> 
> Ken W.
> 
> 


-- 
Alain
-------------------------------------------------
How many of you believe in psycho-kinesis? Raise my hand...

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