I am trying to use blender to simulate the Lycurgus Cup. The cup is an example of dichroic (two-color) glass, and appears green when a light source is on the outside of the cup, and appears red when a light source is inside the cup.

Here is an image of when light is outside and it appears green: Green Lycurgus Cup
(source: britishmuseum.org)

Here is an image of when light is inside and it appears red: Red Lycurgus Cup
(source: britishmuseum.org)

I have created a glass cup in blender. I have made the glass a red color, and then used the colorbands under the Object->Material/Shading->Ramps tab to add green specular and diffuse color. However, this makes the glass appear the same mix of red and green whether I put the light source on the inside or outside the cup. An example can be seen here: blender image

According to the second post here, someone was able to

to fake the effect of a dichroic glass in blender rather easily through the use of a magic procedural texture

but they provide no clues on how to do this (in blender).

Does anyone know how to achieve this effect in blender?


Here is the solution that I ended up going with. Instead of defining a material with the properties that I needed, I used keyframes to change the material color and alpha channel as the light moved inside the cup. Here is the result:

Outside: Green Cup

In the middle: Middle Cup

Inside: Red Cup

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