Dispersion?

[lover05]

I see with the new release of Vray for Rhino 4.0 it is now possible to have dispersive materials. How do I make one to make a diamond look real? or other gems for that matter?

[dalomar_cg]

Re: Dispersion?

Make a normal refractive/glass type material, and then add two more refraction layers (for a total of 3). Make sure that the IOR values of each layer is slightly different than the previous ones. Now you will need to set a transparency color for each one. Instead of using gray scale values as you normally would for transparency, you will need to set the color of the layers to red (255,0,0), green (0,255,0) and blue (0,0,255). It doesn't matter which color you use for each layer as long as each color is used once. Lastly, but most important, in the material options you will need to check Disable Volume Fog. That should do it, hope that helps.

Thats from this thread here
A quick addition to the comments above; the amount of separation of each of those colors is going to depend on the amount of change in the IOR of each of the refraction layers. If you would like a wider dispersion effect, but not as much break between the colors you can try a version with 6 colors in the transparency slot rather than 3. Those three additional colors are 255,255,0 (yellow); 255,0,255 (magenta); 0,255,255 (cyan). Hope this helps.

[joe_b]

Re: Dispersion?

Just to clarify where those colors are coming from - they are the white-complement of the colors of Red- Green- Blue. To calculate the white-complement you simply subtract the color from white. So...

White = RGB(255, 255, 255 )
Red = RGB(255, 0, 0 )

Red_White_Comp = White - Red
= RGB(255, 255, 255 ) - RGB(255, 0, 0 )
= RGB(0, 255, 255 )