Thin Dielectric Sheets
A thin dielectric sheet can be applied to one side of a face to model flat multilayer dielectric structures. Typical applications include radome enclosed antennas and automobile windscreens.
For example,consider a model with two layers. One layer is a good absorber and the second is a good conducting layer. When a ray is incident on the side of the absorber, the reflection is zero. When a ray is incident on the side of the conducting layer, the reflection is near perfect. The transmission coefficient in both cases is zero.
The definition of which side is the front / rear is determined by the normal vector n of the triangles. If one ray is incident in the direction of the normal vector (ray 1) and as a result hits the first layer (index number n - layer with the highest index number). An incident ray in the opposite direction of the normal vector (ray 2) will first hit the layer with the lowest index number.