just to be sure with call backs

mKnifeGroup->setCallback(mCallback);

mKnifeGroup->setCollisionCallback(mButterKnifeGroup, NX_NOTIFY_ALL, true);

so saying setcallback is a way of telling things how they should react when the two objects touch and setCollisionCallback is saying this is the second group that is meant to contact with each other?

is that correct?

Yep. It notifies mCallback of all events when mKnifeGroup is in contact with mBufferKnifeGroup.

could i also say

mKnifeGroup->setCollisionCallback( mKnifeGroup, NX_NOTIFY_ALL, true);

as well, to test other object in the same group are colliding too. I presuming this would work but checking to see?

thanks

also would this crash if i just call

mKnifeGroup->setCollisionCallback(mButterKnifeGroup, NX_NOTIFY_ALL, true);

with out calling mKnifeGroup->setCallBack( mCallback );

before hand, just out of curiosity???