Any plans to have one of these in future releases? I'd like to think I could make one myself, but looking at the other primitives and collision functors, I don't think I have the time / smarts.
Cylinders are actually really hard; especially cylinder/cylinder, which requires solving quadric equations to do them right. Many game physics libraries don't have full support for cylinder collisions, for this reason.
Generally, you can get away with boxes, capsules, and rays for the cases where you would want cylinders. For example, for barrels, use a capsule, but put a box at the very bottom (smaller than the diameter of the cylinder), which will allow the barrel to stand up, but roll when knocked over.
Thanks for the nice tip, I'll give it a try.
Do you think that the crysis 3000 barrels vid (http://www.youtube.com/watch?v=YG5qDeWHNmk) was done using pseudo cylinders?
I don't know whether Crysis solves the cylinder/cylinder, or does some cheat. I tried looking for interpenetrations along the rim of the barrels, but the video is so quick and blurry that it's hard to tell. Note that the simulation isn't stable with that amount of objects, though — the buildings start out disabled, but as soon as they become enabled, the instability is pretty obvious. Which is fairly typical for a physics engine where the focus is on destruction, not construction :-)