Translucent colored glass

UDK lighting can pick up the color from a Material used by a translucent, shadow casting object, and cast it as a kind of caustic onto another surface. This Transmission is calculated automatically. For Lit Materials it uses the Material's Diffuse channel, plus white, linearly interpolated (Lerp) by the Opacity channel to work out the Transmission. For Unlit Materials it uses the Emissive channel, plus white, linearly interpolated (Lerp) by the Opacity channel to work out the Transmission. Modulated Materials are calculated slightly differently, using just the Diffuse or Emissive channel depending on whether they use the Lit or Unlit lighting model. That's a mouthful to digest, certainly, so we are going to do an example which shows on one hand a Lit Material using Translucency, and alongside it, an Unlit Material using Additive mode.

In this recipe we'll be creating a stained glass window effect, based on the concept of Transmission outlined above. First we'll generate...