Mysterious transfiguration of glass

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Mysterious transfiguration of glass // Archive: Tech Forum

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Post by Burisman // May 27, 2007, 1:23am

Burisman
Total Posts: 128
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Hi there. I'm doing something wrong, but can't seem to figure out what...

I followed most of the excellent Jack Edwards' instructions to create a mapped phong shader (I greatly admired his Dickensian glass pane in another thread (http://forums1.caligari.com/truespace/showthread.php?t=3064&highlight=phong+vray+shader)) and he was so kind as to explain how he did it, before turning to the very concrete job of poring concrete on his driveway - good luck Jack!).

Then I created an identical shape, but this time only with a coloured glass shader.

The reason for this is this: for an image - on which I just started - (see attachment 'antigrav'), I want to create some Leiden Jars (they were used in the 18th C to store static electricity). These jars are mainly bottles, wrapped in some kind of metal foil. In some old science museums (e.g. in Leiden, Holland), you still can see them, they are dirty and have all kinds of little scratches etc. So I would like to separate glass from coating to be able to create more variation in the final image. Now the bottles are just green and speckless.

Here comes the funny bit. When, in my test-image I render the panes, but with a little distance between them, the render displays everything as I planned it (before). But at the moment I let the panes touch, only a little bit, not only the overlapping part of the glass pane loses its transparency, but the whole pane. So in this setup it is impossible to combine the effects of two separate shaders.

What really intrigues me is the reason why the effect is not limited to the overlapping part, but affects the whole cube.

Screenshots included. I tinker along and am not in a great hurry, but this question perhaps leads to something which can be of use for others.

I don't even think of calling it a bug ;) ... it's probably me (on Sting's melody) ... :o

Post by Jack Edwards // May 28, 2007, 4:41pm

Jack Edwards
Total Posts: 4062
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The concrete went pretty well. Got one section done, but going to have to put off the 2nd section until next week. :)

Interesting about the intersecting planes. Couple of things come to mind:
Try upping the QMC Depth to 10 (or 6 if your computer balks at 10 ;))
Try toggling single-sided.

The other thought is that your glass shader just looks like it's green, so you could add green to your color map for the glass with the mapped shader and in your paint program up the clip the low end of the diffuse map values at a high enough value that the green will tint even where it's totally transmissive.

Hope that helps!

-Jack.
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