But anyway, due to limited time this is pretty much as finished as my entry will ever be. Others will have to make the really cool stuff :).
So this is my barebones trebuchet system. The pouch is faked, there was no way I could complete this within my schedule if I added softbody interaction to the mix. So the projectile is attached by a keyframed constraint that turns off at the appropriate time. I know it's a big fat cheat, but.. oh well.
The rest is more or less dynamic though. Here's a rundown of the setup:
green: hinge constraint
yellow: pin constraint
red: pin constraints for firing-arm rope
blue: pin constraints for projectile rope
The firing-arm is kept in place by having the lockingpin collide with a pair of eyescrews (marked pink in 2nd image). The lockingpin and firing-arm is connected by a rigidbody rope (marked red). The rigidbody rope consists of simple geometry connected via pin constraints (see picture 3 for details, pin constraints marked with white).
At one time I had a solution where the machine fired as I pulled the lockingpin out, but I opted for just keyframe disabling the constraint in the end. For me it's enough to know that it works "physically correct" if I needed it, I just wasn't going to sit through simulation after simulation looking at that key being pulled out. Takes long enough to compute as is :).
This whole project is about a days worth of effort. I don't know that much about (Maya) dynamics, that's why I was so interested in trying this out.
I learnt that I cannot get softbody ropes to interact with rigidbody objects. It is seemingly impossible to cock the firingarm by pulling an attached softbody rope. If anyone has a way to make this happen I'd be very interested, it seems like a simple action but I found little that worked.
So I ended up switching to rigidbody ropes instead, which works pretty well. The ropes are clearly extremly simplified, for "pretty" results they shouldn't be rendered but act as influence objects on a smoothskinned tube. Also obviously more segments are needed. But the simplified ropes made for quicker calculations, so horray.
Oh, also not all objects collides with eachother. Each rope (projectile- and firingarm-rope) only collides with itself and the ground, I know that's a cheat but I wasn't going to sit through all that collision.
Below is the link to the movie, and the project files. I hope by freely giving away the scene files someone outhere can learn something or other. Or learn what not to do perhaps.
Here's the movie (2,09 mb):
And the project can be aquired here (http://gaggle.dhs.org/hosted/trebuchet/gaggle_trebuchetProject.zip) (604 kb). It's Maya 5.0.1, and all rigidbodies are pre-cached.
Finally I'll just link a couple of playblasts I outputted. It turned out hitting that damned wall was damn difficult. Tiny changes in weight and tension generated (at times) wildely different results. I haven't optimized the playblasts so filesizes are on the large size.
blast2_cocking (http://gaggle.dhs.org/hosted/trebuchet/blast2_cocking.avi) (1.18 mb) - blast3_firstShot (http://gaggle.dhs.org/hosted/trebuchet/blast3_firstShot.avi) (634 kb) - blast5_completeDisaster (http://gaggle.dhs.org/hosted/trebuchet/blast5_completeDisaster.avi) (4.02 mb)