pbrt build process
I built pbrt on the myth machines, and then on my own Linux machine, with no problem.
Speeding up the rendering process
I set the image size to 200*200, with 2 sample rays per pixel, which makes pretty fast.
I also wrote a simple script to be able to render/convert to tif/display the resulting tif with just one command.
Experimentation
Obtaining the first configuration was pretty straightforward. However I had trouble getting a correct image for configuration 2.