Welcome to the arena, Mitsuba!
Obviously Mitsuba has many more features than appleseed and, I believe, is generally more advanced. What strikes me though is the similarity, both in the philosophy and in the realization, between Mitsuba and appleseed. From what I could gather:
- Both are large, platform-independent C++ frameworks aiming at supporting a variety of rendering algorithms (called "integrators" in Mitsuba, inheriting the term from PBRT).
- Both are aiming at generality and robustness.
- Both provide a Qt-based graphical user interface and a command line tool.
- Both feature a scene description language based on XML (and Mitsuba also seems to use the heavy-duty Xerces-C XML parser that's also used in appleseed).
Massive congrats to Wenzel for pulling this off. I'm definitely looking forward to see where Mitsuba will be going in the future.