Another intended GSoC applicant here. Would a hardware-centric project be mentor-able for Summer of Code?
(On that note, I'm hoping I shouldn't have posted this in Integration&Hardware, as it pertains to GSoC.) I'm thinking something along the lines of getting Processing working with devices other than Arduino, Wiring--maybe XMOS, as I already have a dev board?
Full disclosure: this second proposal is a result of fanboy tendencies towards Sparkfun... How about integration with application-specific hardware, such as the PICASO graphics controllers intended for 4D Graphics Lang? Possible approaches would be shoehorning custom code onto the controllers, or an implementation requiring an external host run the desired Processing code, but pass commands for visual output to PICASO. A library for common draw functions to work with 4DGL could be put together to help meet this end.
