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mrTortex
Member
Hello.
I have Googled :) I am looking for an example of using the Chipmunk Post Solve Callback to work out collision force. For example, two balls hit, force is displayed on a label. Is anyone aware of anything? I've seen many threads which don't resolve, but can't find a working example.
Thanks :)
Using cpArbiterTotalImpulse seems to be the usual way to get the total force vector of a collision, you could then do something like calculate the length of the vector to get a scalar value for printing....
Seems to be a thread about some of the problems with it though:
http://www.slembcke.net/forums/viewtopic.php?f=1&t=1076&p=4960
oh hmmm just the velocity? I actually use this method to determine whether to play a sound in the BEGIN part of the collision.
If you're just looking the for the larger velocity, just grab both shape's velocity vectors and compare against the value that cpvlengthsq gives you on each vector.
If want a "better" value where both speeds are taken into account, that way if two active shapes hit but they were both moving in the same direction, then the value won't be unnecessarily large when it really isn't, then use this:
cpFloat relVelocity = cpvdistsq(shape1->body->v, shape2->body->v);
mrTortex
Member
Hello.
That works :) I now have a label spitting out vect lengths at me. The odd thing is the length are either radically high (1677789546 etc) or incredibly low (-575986095). If I divide the number by anything to try to get some control over it, the vect then sticks at 0.
Ideally I'd like to round it down so it's within a more manageable range, so I can have a conditional which says if the vect >= 10, your piloting skills need work - else, well done. Trying to do that with such huge numbers that change drastically when the dynamic object rotates a fraction of a degree is hard.
But, I'm closer so thank you. :)
do you use cpvdistsq or cpvlengthsq? if so you may want to use cpvdist or cpvlength instead.... the square roots of the former funcs; values that make a bit more sense to the user.
Yeah so it was just the formatting of your string, it's %.2f
2 represent the number of decimal places you want, you can use a smaller or larger number if you wish.
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