void BulletPhysics::BulletInternalTickCallback(btDynamicsWorld* world, btScalar timeStep)
{
// called after bullet sdk performs its internal step
CB_ASSERT(world);
CB_ASSERT(world->getWorldUserInfo());
BulletPhysics* bulletPhysics = static_cast<BulletPhysics*>(world->getWorldUserInfo());
CollisionPairs currentTickCollisionPairs;
// look at all existing collisions
btDispatcher* dispatcher = world->getDispatcher();
const int numManifolds = dispatcher->getNumManifolds();
for (int i = 0; i < numManifolds; i++)
{
// get the manifold which is the data corresponding to a contact point between two colliders
const btPersistentManifold* manifold = dispatcher->getManifoldByIndexInternal(i);
CB_ASSERT(manifold);
// get the colliding bodies
const btRigidBody* body0 = static_cast<const btRigidBody *>(manifold->getBody0());
const btRigidBody* body1 = static_cast<const btRigidBody *>(manifold->getBody1());
// swap them if need be
const bool swapped = body0 > body1;
const btRigidBody* sortedBody0 = swapped ? body1 : body0;
const btRigidBody* sortedBody1 = swapped ? body0 : body1;
// insert the collision pair into the set
const CollisionPair pair = std::make_pair(sortedBody0, sortedBody1);
currentTickCollisionPairs.insert(pair);
// if this is a new contact, send an event
if (bulletPhysics->m_PreviousTickCollisionPairs.find(pair) == bulletPhysics->m_PreviousTickCollisionPairs.end())
{
bulletPhysics->SendCollisionPairAddEvent(manifold, body0, body1);
}
}
CollisionPairs removedCollisionPairs;
// use set difference to see which collisions existed last tick but are no longer colliding
std::set_difference(bulletPhysics->m_PreviousTickCollisionPairs.begin(), bulletPhysics->m_PreviousTickCollisionPairs.end(),
currentTickCollisionPairs.begin(), currentTickCollisionPairs.end(),
std::inserter(removedCollisionPairs, removedCollisionPairs.begin()));
// send collision exit events
for (auto it = removedCollisionPairs.begin(); it != removedCollisionPairs.end(); ++it)
{
const btRigidBody* body0 = it->first;
const btRigidBody* body1 = it->second;
bulletPhysics->SendCollisionPairRemoveEvent(body0, body1);
}
// update the collision pairs
bulletPhysics->m_PreviousTickCollisionPairs = currentTickCollisionPairs;
}
void BulletOpenGLApplication::CheckForCollisionEvents() {
// keep a list of the collision pairs we
// found during the current update
CollisionPairs pairsThisUpdate;
// iterate through all of the manifolds in the dispatcher
for (int i = 0; i < m_pDispatcher->getNumManifolds(); ++i) {
// get the manifold
btPersistentManifold* pManifold = m_pDispatcher->getManifoldByIndexInternal(i);
// ignore manifolds that have
// no contact points.
if (pManifold->getNumContacts() > 0) {
// get the two rigid bodies involved in the collision
const btRigidBody* pBody0 = static_cast<const btRigidBody*>(pManifold->getBody0());
const btRigidBody* pBody1 = static_cast<const btRigidBody*>(pManifold->getBody1());
// always create the pair in a predictable order
// (use the pointer value..)
bool const swapped = pBody0 > pBody1;
const btRigidBody* pSortedBodyA = swapped ? pBody1 : pBody0;
const btRigidBody* pSortedBodyB = swapped ? pBody0 : pBody1;
// create the pair
CollisionPair thisPair = std::make_pair(pSortedBodyA, pSortedBodyB);
// insert the pair into the current list
pairsThisUpdate.insert(thisPair);
// if this pair doesn't exist in the list
// from the previous update, it is a new
// pair and we must send a collision event
if (m_pairsLastUpdate.find(thisPair) == m_pairsLastUpdate.end()) {
CollisionEvent((btRigidBody*)pBody0, (btRigidBody*)pBody1);
}
}
}
// create another list for pairs that
// were removed this update
CollisionPairs removedPairs;
// this handy function gets the difference beween
// two sets. It takes the difference between
// collision pairs from the last update, and this
// update and pushes them into the removed pairs list
std::set_difference( m_pairsLastUpdate.begin(), m_pairsLastUpdate.end(),
pairsThisUpdate.begin(), pairsThisUpdate.end(),
std::inserter(removedPairs, removedPairs.begin()));
// iterate through all of the removed pairs
// sending separation events for them
for (CollisionPairs::const_iterator iter = removedPairs.begin(); iter != removedPairs.end(); ++iter) {
SeparationEvent((btRigidBody*)iter->first, (btRigidBody*)iter->second);
}
// in the next iteration we'll want to
// compare against the pairs we found
// in this iteration
m_pairsLastUpdate = pairsThisUpdate;
}
