Thanks for the comments.

The 3d-rendering is done in 3delight. Its Renderman compliant shading language gives a lot of flexibility for writing custom shaders. But I wrote several helper programs myself in C++ and Python.
I have developed this style over the course of several months. The reason why it took so long is that I usually try to develop a whole workflow, which later allows me to make similar maps very quickly.

Do you have any suggestions for improvements?