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From a CGTALK Post
Jeff Patton - Photon phreak  
Join Date: Aug 2002
Location: S.Carolina, USA
Posts: 765

ssalo: very nice indeed. You can do wonders with the scanline, for sure. Can you post any of your settings? Especially that translucent one from the other day.

I want to share the settings for the glass I made so others can experiment as well, so here goes.

Select to use Mental Ray for the renderer, then

(1) Create a Raytrace material. Set it up just as you would normally for glass. Two sided, and make the diffuse almost pure white. Thats it.
(2) In the Mental Ray Connection roll out add a Parti Volume (physics) shader to the Photon Volume slot and the Volume slot as well.
(3) Settings for the Parti Volume located in the Photon Volume rollout:
Mode is set to 2. I forget the name of this mode, but it's listed in that .pdf file I linked to earlier. Scatter color is the default grey.
Extinction: You will have to adjust this based upon the shape & size of the item you are applying the texture to. I found mine to work best at 1.5
The only other points I adjusted were the minimum step length (2.0), and the maximum step length (8.0). Again, you will probably have to adjust these based on your specific model.
(4) Settings for the Parti volume shader located in the volume rollout:
Mode is set to 0
Scatter color: Make this the color you want to be scattered inside the object. I made mine dark blue.
Extinction: You will have to adjust to taste, but I set mine at 1.0

Minimum step length: 0.1
Maximum step length: 5.0

Thats it for the material itself!

Now apply this material to your object and make sure the object is set to generate caustics.

Next, you only need one light to shine on your model. I used a mental ray area spotlight, but a regular spotlight will work too.

I enabled raytrace shadows.

Under the mental ray indirect illumination rollout of the light:
UNCHECK the use global settings. The "on" box below will be enabled. I set the energy to 50000, decay at 2.0, caustic photons at 100000 (you will need to adjust to your scene). Global illumination photons are at 10000.

Once ALL of this is done, now your ready to render. Make sure you've enabled caustics in the indirect illumination rollout of the mental ray renderer. I set the samples to 64 on mine.

No Final gather.

Thats it, hit render and post your cool creations so I can see them!

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