On Mon, 28 Dec 2009 12:59:15 -0500
Alain <aze### [at] qwertyorg> wrote:

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

No, transmit is 0, filter is 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?

No. Color is 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.

Yes, I set the ambient value to 0. The amplification was still there.

I just found a solution, but I don't really know why it is one. I'll
investigate a bit more:

I have enabled Fresnel reflection now, and the amplification disappeared
completely! The image is now quite acceptable.

Thanks for the suggestions, Alain! And best wishes for the holidays.
John

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