This simple star represents about a month's worth of work. It was produced using Aqsis, an open source Renderman renderer. The actual program to make the star is actually quite simple. Almost all of the work was actually because I wrote a Python wrapper around the Aqsis library so that I could make Renderman calls from Python directly.
The tricky part in writing the wrapping code was that the Renderman C interface makes extensive use of C's variadic ... style of passing arguments for passing in extended parameter information. Luckily, the Renderman interfaces also specifies the Ri*V style of calls for passing parameters across, without which the wrapper would have been pretty much impossible to write.
All parameters passed in this way are represented using void pointers to low level C types, eg, floats, ints, etc. In particular, when passing in a list of elements, the underlying type actually passed across the interface is generally an array of floats, or ints, or whatever, which are all the same type and contiguously stored in memory. Of course, Python makes no such guarantees about how it stores its types, or that types in the same list are even the same type. The problem then, is converting whatever Python types are passed in into void *'s that can be safely passed across the Renderman C interface.
The way this problem was solved was to essentially maintain map of dynamic conversion objects, which we can clone and allow us to dynamically (and virtually) convert the Python type to the underlying C type, as well as doing any copying, conversion, and memory allocation necessary to store the converted values for the life of the Renderman function call. Another map is maintained which maps the names of Ri function names and parameters to the types that they expect, configured by an external XML file. The Python wrapper can then lookup the necessary types to convert to at call time, perform any conversions necessary, and safely make the underlying C call.
The end result is I can iterate a lot faster. The actual program to generate this star only took a few minutes to write. I'm hoping to get curved surfaces exposed soon and can thus start trying to make higher quality renderings of Jarvis' legs.
