Next step is to place a hole (air) in object #4. Insert object #5 of type Cylinder Volume with the following parameters.

Ref Object: -1
Y position: 5
Z position: 40
Tilt About X: 90
Material: Blank (leave empty)
Front R: 2
Z length: 10
Back R: 2

To make the overlapping volume between the Rectangular Volume (#4) and the Cylinder Volume (#5) air, the Cylinder Volume has to be listed after the Rectangular Volume, as it is in this case. Consult the manual for more detailed information about the volume nesting rule.

Let’s insert a Source Rectangle to the left of object #1 to send rays though the pipe. Make object #6 of type Source Rectangle with the following parameters.

Ref Object: -5 (referenced to the Null object)
Z position: -10
# Layout Rays: 20
# Analysis Rays: 400000
X Half Width: 4.8
Y Half Width: 4.8
All other parameters: Default

The zoomed layout shows TIR (total internal reflection) for certain rays at the edge of the hole, because the refractive index of the hole is lower than that of the rectangular volume.