View Full Version : Dielectric Artifacts?

02 February 2006, 07:23 AM
I made a simple scene with a galss and green liquid to test out some caustic effect and I am getting a bad artifact in the render that I can not fix. You can see it in the green fluid. Does anyone have any suggestions as to what to try?

02 February 2006, 07:32 AM
it looks to me like the water geometry is intersecting with the glass geom. Try offseting the water surface a bit (use the sculpt tool with a low displacement value and press Flood)

02 February 2006, 09:16 AM
No, it's not correct.
Just delete one surface and set IOR_in 1.333 and IOR_out 1.5 (or your ior for glass and water) for glass surface that contact with water.

02 February 2006, 10:27 AM
ah, so a correct glass geometry would be like this: ?

the black line = dielectric with ior_out = 1 (air) and ior_in = 1.5 (glass)
the gray line = dielectric with ior_out = 1.5 (glass) and ior_in = 1.33 (water)
the red line = dielectric with ior_out = 1 and ior_in = 1.33

is this glass structure correct?

02 February 2006, 11:54 AM
Yes, it's correct.

02 February 2006, 06:09 PM
Yashu - you were right. The geometry was just barely intersecting. The new pic is below. I had originally made the geometry as puppet described but was unhappy with the results so I then made a glass and modeled the liquid inside instead. The picture on the right is using puppets method.

02 February 2006, 09:24 PM
Sorry, what is dielectric?

02 February 2006, 11:35 PM
A dialectric material is a physically correct Mental Ray shader used to simulate glass and liquids.

02 February 2006, 08:17 AM
:) I suppose right image is more correct :) and computed faster.

02 February 2006, 07:45 PM
Puppet - you are right, your method is more physically accurate and end the end looks better. :shrug:

Thanks for the help.

03 March 2006, 06:52 PM
As I remember this effect can be archived in a few step with l-glass.. I mysefl do not like this shader much for buggy thing but the fact It is a good dielectric shader

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