HDK: The Houdini Development Kit (C++ development kit) is a paid license option for the Houdini toolkit. There is an official SESI mailing list, some limited html docs supplied with the Houdini HDK, and if you ask SESI they can provide some examples from past HDK courses that they hold about once a year in LA- or anywhere they can rustle up a big enough attendence to justify it and big down the cost. The HDK can be used to used to write any type of operator within Houdini and it can also be us