POV Manual Quote...

6.11.11.2.13  Pretrace
To control the radiosity pre-trace gathering step, use the keywords
pretrace_start and pretrace_end within the radiosity{} block. Each of
these is followed by a decimal value between 0.0 and 1.0 which specifies
the size of the blocks in the mosaic preview as a percentage of the
image size. The defaults are 0.08 for pretrace_start and 0.04 for
pretrace_end 


Yes, but does the pretrace affect the quality of radiosity or is it just
a mosaic effect for the render-window? 

It's not quite clear from the above if smaller values will give better
results. 

I know for sure it will generate smaller squares in the mosaic!

object {
   Grey_Matter
   photons { target Need_More_Info }
}

Thanks

-- 
(MIKA) Marc Champagne
marcch.AT.videotron.DOT.ca
Montreal, CANADA

Post a reply to this message

"Marc Champagne" <nos### [at] pleasecom> wrote in message
news:Xns### [at] 204213191226...
>
> 6.11.11.2.13  Pretrace
> To control the radiosity pre-trace gathering step, use the keywords
> pretrace_start and pretrace_end within the radiosity{} block.
>
>
> Yes, but does the pretrace affect the quality of radiosity or is it just
> a mosaic effect for the render-window?

It is doing a sampling of areas, so yes, it is a quality factor. Pretrace
isn't the same as mosaic preview, only looks it.

Post a reply to this message

Marc Champagne wrote:
> 
> ...does the pretrace affect the quality of radiosity or is it just
> a mosaic effect for the render-window? 
> 
> It's not quite clear from the above if smaller values will give better
> results.

In some cases, smaller pretrace_end values will help smooth artifacts 
(slightly); in other cases, a smaller value has no appreciable effect. 
Obviously, in all cases, a lower value will increase rendering time.

-Xplo

Post a reply to this message

Marc Champagne wrote:
> 
> [...]
> 
> Yes, but does the pretrace affect the quality of radiosity or is it just
> a mosaic effect for the render-window?
> 
> It's not quite clear from the above if smaller values will give better
> results.
> 

In general you can say: lower pretrace_end -> higher quality and slower
render.  But how much you gain depends on the other settings.  As a rule
of thumb you can say a low error_bound also profits from low
pretrace_end.  A high error_bound combined with a low pretrace_end is just
a waste of time.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

Post a reply to this message