I believe there are a number of libraries for that, for some major 3D file formats, but I haven't dug the topic, so some googling is required. See also the https://forum.processing.org/topic/contributed-libraries topic, giving a way to reach the old list of contributed libraries.

i while ago i wrote a method to send 3d points from an array to rhino/grasshopper and retain the array format,
i used OSC (oscP5, and gHowl for grasshopper)

the purpose of that was to send the points from p5 to rhino in real time, so its not exactly exporting, but live communication. i hope it helps

http://www.grasshopper3d.com/forum/topics/processing-to-grasshopper-real-time-communication?xg_source=activity

there are some other guys who export stuff in OBJ format to render in Octane render software. i suppose obj can save points too.
their library can be found here
http://muehlseife.blogspot.gr/2011/03/processing-obj-exporter-octane-render.html