> Hello guys and gals,
>
> I was playing around with a simple scene for a Holiday card, and have two
> problems. This years' focus was on trying glasses and contents as
> believable as possible.
>
> The scene is a PNG background image of some fireworks, and two glasses in
> the front. The PNG is defined with an ambient light of 1, there is no
> other light source in the scene.
>
> Strangely, the image of the PNG coming through the glass seems to be
> amplifying: Without the glasses, the image shows fine, through the
> glass, the image saturates completely!
>
> And the second problem is an artifact appearing in the middle line (row)
> of pixels. This artifact seems to depend on the size of the image. In the
> image I uploaded, it's not very visible (right side of each glass). In a
> 1200x900 version, it runs over the entire width (I'll render another one
> of these later).
>
> The output images are:
>
> http://jcoppens.com/misc/with_glasses.png
> http://jcoppens.com/misc/no_glasses.png
>
> I'm running POV-ray 3.7beta34, on Linux.
>
> John
>
> PS: I still have to set ambient of the liquid to 0...

Do your glass pigment have both filter and transmit?
Do they add up to more than 1?

Normaly, the sum of transmit and filter must total at most 1, usualy to 
a value slightly less than that, like filter + transmit <= 0.999. If it 
adds up to more than 1, it will have an amplification effect. As you 
cross 4 surfaces as you trverse the glass, the amplification will appens 
4 times. So, even a value just slightly over 1 can have a very 
niticeable effect.

Is the colour part larger than 1?

If it's larger than 1, it will also have an amplification effect.

Try a pigment of rgbt 1 or rgbf 1 for your glass and see what it does.
You can also try rgbft<1,1,1,0.5,0.5>

The ambient part for a transparent object is usualy barely dicernible, 
if at all.



Alain

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