Ken wrote:

> Nieminen Mika wrote:
>
> >   And btw, MY BIGGEST problem with povray 3.1 is that there's no povhelp
> > program anymore, and that really PISSES ME OFF! Sorry, I just had to
> > complain.
> >   I still can't use the new features of pov3.1 because I DON'T KNOW HOW,
> > damn it!
>
> Why that's just not true. There is documentation for Pov v3.1. The
> layout is different but it exists as it did before. It even functions
> the way it did in in v3.0x where you can place the cursor over a
> keyword, press f1, and the documentation menu pops up giving you a
> selection of relevant topics to choose from. I am not happy with the
> way it's been structured in a non-scrolling format as it was but the
> information is still being supplied. It appears you missed something
> somewhere.
>
> Ken Tyler

In support ov my previous post I just copied this from the v3.1
docs concerning the use of the New with Pov v3.1 function "Media"


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Multiple Density vs. Multiple Media

It is possible to have more than one media specified per object and it
is legal to have more than one density per media. The effects are quite
different. Consider this example:

  object{MyObject
    pigment{rgbf 1}
    interior{
      media{
        density{Some_Density}
        density{Another_Density}
      }
    }
  }

As the media is sampled, calculations are performed for each density
pattern at each sample point. The resulting samples are multiplied
together. Suppose one density returned rgb<.8,.8,.4> and the other
returned rgb<.25,.25,0>. The resulting color is rgb<.2,.2,0>. Note
that in areas where one density returns zero, it will wipe out the
other density. The end result is that only density areas which overlap
will be visible. This is similar to a CSG intersection operation. Now
consider

  object{MyObject
    pigment{rgbf 1}
    interior{
      media{
        density{Some_Density}
      }
      media{
        density{Another_Density}
      }
    }
  }

In this case each media is computed independently. The resulting colors
are added together. Suppose one density and media returned rgb<.8,.8,.4>
and the other returned rgb<.25,.25,0>. The resulting color is
rgb<1.05,1.05,.4>. The end result is that density areas which overlap
will be especially bright and all areas will be visible. This is similar
to a CSG union operation. See the sample scene
scenes/interior/media/media4.pov for an example which illustrates this.

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Ken Tyler

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