Ilmari Karonen wrote:
> 
> Bob Hughes wrote in message <369ECBDE.8FD96178@aol.com>...
> >I understand the basic scaling syndrome of keeping media density in sync
> >with container objects, but I've been lost too many times trying the
> >containerless "air", since each scene is not the same as the last.
> 
> One thing you have to remember is to scale the densities according to
> the scale of the scene. I've found that to have 50% of light absorbed
> by a media of thickness "dist" the appropriate definition is
>   media { absorption 1/(sqrt(2)*dist) }

Okay, I'll try that out. Thanks for keeping me going. (I did know to
scale, maybe everyone will catch on to that procedure eventually)

> I suppose the same applies to scattering media. Since the density is
> constant, you can speed up rendering by using "intervals 1". Oh, and
> don't use the fade_distance keyword in interior if you want a realistic
> scene - the formula used has nothing to do with realistic absorption.
> 

Watch out with the intervals being lower than the number of
light_sources. Not sure yet of the correlation, but I have had crashes
using a intervals integer less than the lights number.

> BTW, whatever were the povray designers thinking when they implemented
> light_source fading? For some reasong the realistic formula
>   attenuation = pow( fade_distance/d, fade_power )
> was replaced by
>   attenuation = 2/( 1 + pow( d/fade_distance, fade_power ) )
> which has AFAIK absolutely no connection to reality, even though it does
> approximate the proper formula at distances far greater than fade_distance
> as long as you remember to divide the brightness by two.. (The same cannot
> be said for the aforementioned interior fading.)
> 

Any POV Team member know why or can confirm this?

> --
> Ilmari Karonen (ilt### [at] scifi)
> (not r### [at] hakasaunalahtifi as the IRTC comments list claims..)
> http://www.sci.fi/~iltzu/

-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/POVring.htm
=Bob

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