好的
我要开始新篇了
新篇是Bullet的
刚开始看Bullet时 代码不熟 看后忘前 不过 怎么说呢 那我就每天看 草
于是 我就明白了
先看看那个step函数：
1
void btDiscreteDynamicsWorld::internalSingleStepSimulation(btScalar timeStep)
2
{
3
4 BT_PROFILE("internalSingleStepSimulation");
5
6
if(0 != m_internalPreTickCallback) {
7 (*m_internalPreTickCallback)(this, timeStep);
8
}
9
10 /**////apply gravity, predict motion
11 predictUnconstraintMotion(timeStep);
12
13 btDispatcherInfo& dispatchInfo = getDispatchInfo();
14
15 dispatchInfo.m_timeStep = timeStep;
16 dispatchInfo.m_stepCount = 0;
17 dispatchInfo.m_debugDraw = getDebugDrawer();
18
19
20 createPredictiveContacts(timeStep);
21
22 /**////perform collision detection
23 performDiscreteCollisionDetection();
24
25 calculateSimulationIslands();
26
27
28 getSolverInfo().m_timeStep = timeStep;
29
30
31
32 /**////solve contact and other joint constraints
33 solveConstraints(getSolverInfo());
34
35 /**////CallbackTriggers();
36
37 ///integrate transforms
38
39 integrateTransforms(timeStep);
40
41 /**////update vehicle simulation
42 updateActions(timeStep);
43
44 updateActivationState( timeStep );
45
46 if(0 != m_internalTickCallback) {
47 (*m_internalTickCallback)(this, timeStep);
48 }
49
}
50 看看里面几个重要的函数：
1 predictUnconstraintMotion(timeStep) ：给每个物体加重力作用力
2 createPredictiveContacts(timeStep) ：和ccd有关 处理物体在高速运动时的碰撞
3 performDiscreteCollisionDetection()：此函数做碰撞 我们来看看
void btCollisionWorld::performDiscreteCollisionDetection()
{
BT_PROFILE("performDiscreteCollisionDetection");
btDispatcherInfo& dispatchInfo = getDispatchInfo();
updateAabbs();
computeOverlappingPairs();
* dispatcher = getDispatcher();
{
BT_PROFILE("dispatchAllCollisionPairs");
if (dispatcher)
dispatcher->dispatchAllCollisionPairs(m_broadphasePairCache->getOverlappingPairCache(),dispatchInfo,m_dispatcher1);
}
}
1) updateAabbs()：
把要参加broad碰撞的物体放进paircache，此时没有进行任何碰撞检测，仅仅是把物体加进paircache（addOverlappingPair）同时，放进ghost的paircache里
if (m_ghostPairCallback)
m_ghostPairCallback->addOverlappingPair(proxy0,proxy1);
在这个阶段可以设置一个回调函数，用于过滤一些特定物体
SIMD_FORCE_INLINE bool needsBroadphaseCollision(btBroadphaseProxy* proxy0,btBroadphaseProxy* proxy1) const
{
if (m_overlapFilterCallback)
return m_overlapFilterCallback->needBroadphaseCollision(proxy0,proxy1);
bool collides = (proxy0->m_collisionFilterGroup & proxy1->m_collisionFilterMask) != 0;
collides = collides && (proxy1->m_collisionFilterGroup & proxy0->m_collisionFilterMask);
return collides;
}
m_overlapFilterCallback就是那个回调函数
2) computeOverlappingPairs()：
该函数执行broad碰撞，也就是类似于AABB的粗线条碰撞，以此过滤paircache中不用进行narrow碰撞的pair
3) dispatcher->dispatchAllCollisionPairs(m_broadphasePairCache->getOverlappingPairCache(),dispatchInfo,m_dispatcher1):
该函数进行narrow碰撞，也就是精确碰撞，在这里，我们也可以设置回调，以过滤掉某些物体的精确碰撞
void btCollisionDispatcher::defaultNearCallback(btBroadphasePair& collisionPair, btCollisionDispatcher& dispatcher, const btDispatcherInfo& dispatchInfo)
{
btCollisionObject* colObj0 = (btCollisionObject*)collisionPair.m_pProxy0->m_clientObject;
btCollisionObject* colObj1 = (btCollisionObject*)collisionPair.m_pProxy1->m_clientObject;
if (dispatcher.needsCollision(colObj0,colObj1))
{
btCollisionObjectWrapper obj0Wrap(0,colObj0->getCollisionShape(),colObj0,colObj0->getWorldTransform());
btCollisionObjectWrapper obj1Wrap(0,colObj1->getCollisionShape(),colObj1,colObj1->getWorldTransform());
//dispatcher will keep algorithms persistent in the collision pair
if (!collisionPair.m_algorithm)
{
collisionPair.m_algorithm = dispatcher.findAlgorithm(&obj0Wrap,&obj1Wrap);
}
if (collisionPair.m_algorithm)
{
btManifoldResult contactPointResult(&obj0Wrap,&obj1Wrap);
if (dispatchInfo.m_dispatchFunc == btDispatcherInfo::DISPATCH_DISCRETE)
{
//discrete collision detection query
collisionPair.m_algorithm->processCollision(&obj0Wrap,&obj1Wrap,dispatchInfo,&contactPointResult);
} else
{
//continuous collision detection query, time of impact (toi)
btScalar toi = collisionPair.m_algorithm->calculateTimeOfImpact(colObj0,colObj1,dispatchInfo,&contactPointResult);
if (dispatchInfo.m_timeOfImpact > toi)
dispatchInfo.m_timeOfImpact = toi;
}
}
}
}
这个是默认的callback所做的活，正如bulletManual上所说，可以换成我们自己的callback
void setNearCallback(btNearCallback nearCallback)
{
m_nearCallback = nearCallback;
}
另外，还可以重载btCollisionDispatcher，重写其
virtual bool needsCollision(const btCollisionObject* body0,const btCollisionObject* body1);
virtual bool needsResponse(const btCollisionObject* body0,const btCollisionObject* body1);
virtual void dispatchAllCollisionPairs(btOverlappingPairCache* pairCache,const btDispatcherInfo& dispatchInfo,btDispatcher* dispatcher) ;
从而完全定制其行为
好 暂时over
posted on 2013-01-10 20:06
野猪红 阅读(1618)
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