Iridescence: Part I, the CD effect

Iridescence. We all know what it is, and never knew what it was called. Technically it is the physical effect of a color changing based on its viewing angle. We see this in CD's, insects, bubbles, cars and so on. Here I'm going to explain how you can do this in 3DS Max.

Iridescence shader on torus knot

When I started thinking about the shader, I began to think of how iridescence works in reality. This effect happens due to objects having multiple layers with different reflections. So the shader that would work best for this would be a multi-layered shader. The one I used here was Shellac for the controlled layering. Essentially I created 3 A&D materials that were highly reflective and layered them. Each with different reflection colors, red, green, and blue. The real trick to getting that iridescent color is by rotating the anisotropic reflection in each shader with a different rotation amount. Just enough to blend the rgb values gives a believable rainbow spectrum.


But just how do you get that cd reflection to scatter from the center out? This is where the gradient ramp comes in. Choose a radial spread to get the right results. It's placed in the bump map slot, and this is what scatters the reflection in a beliveable way. And as always you have to apply a UVW map onto your object so it knows where the radial gradient is starting from.

Happy texturing!