BulletPhysic:联系力/冲动

Question

我想检测一个(球)何时接触另一个物体(目标),我想知道那个接触的冲动.

我知道有三种方法来检测联系人

gContactAddedCallback

要么

    int numManifolds = m_dynamicsWorld->getDispatcher()->getNumManifolds();
    for (int i=0;i<numManifolds;i++)
    {
        btRigidBody* obA = static_cast<btRigidBody*>(contactManifold->getBody0());
        btRigidBody* obB = static_cast<btRigidBody*>(contactManifold->getBody1());
        // May be there is contact obA and obB

        btPersistentManifold* contactManifold =  m_dynamicsWorld->getDispatcher()->getManifoldByIndexInternal(i);
        int numContacts = contactManifold->getNumContacts();
        for (int j=0;j<numContacts;j++)
        {
            btManifoldPoint& pt = contactManifold->getContactPoint(j);
            if (pt.getDistance()<0.f)
            {
                // One contact point is inside of another object
                // But some contacts are ignored
            }
        }
    }

要么

检查线性和角速度变化.(不清楚是否有接触和什么物体使速度发生变化,是物体还是阻尼,重力或某些力场.

---

我希望有联系信息,包括联系人冲动.我注意到在1帧模拟中解决了一些接触,其他需要2帧,脉冲则低两倍.(我得到了它调试代码.)我会很乐意得到一个总冲动的联系通知.

我列出的所有方法都没有为我提供联系方式的完整信息.有一段时间它会在球飞近目标时发射,甚至不会碰到目标.

什么是预期的方法呢？

如果接触能量很高,这些信息可用于播放冲击声或开始一些动画.

Answer 1

这段代码应该为您指明可能的方向

// some global constants needed

enum collisiontypes {
    NOTHING         = 0,    // things that don't collide
    BALL_BODY       = 1<<2, // is ball
    TARGET_BODY     = 1<<3  // is target
};

int ballBodyCollidesWith    = TARGET_BODY | BALL_BODY;  // balls collide with targets and other balls
int targetBodyCollidesWith  = BALL_BODY;    // targets collide with balls

// ...
// bodies creation

dynamicsWorld->addRigidBody(ballBody, BALL_BODY, ballBodyCollidesWith);

dynamicsWorld->addRigidBody(targetBody, TARGET_BODY, targetBodyCollidesWith);

//...
// find out whether a ball collides with a target

int numManifolds = m_dynamicsWorld->getDispatcher()->getNumManifolds();
for (int i=0;i<numManifolds;i++)
{
    btRigidBody* obA = static_cast<btRigidBody*>(contactManifold->getBody0());
    btRigidBody* obB = static_cast<btRigidBody*>(contactManifold->getBody1());
    // May be there is contact obA and obB

    // ignore bodies that are not balls or targets
    if (
        (!(obA->getCollisionFlags() | BALL_TYPE) && !(obB->getCollisionFlags() | BALL_TYPE))    // there is no BALL_TYPE colliding
        ||
        (!(obA->getCollisionFlags() | TARGET_TYPE) && !(obB->getCollisionFlags() | TARGET_TYPE))    // there is no TARGET_TYPE colliding
        )
        continue; // no more searching needed

    btPersistentManifold* contactManifold =  m_dynamicsWorld->getDispatcher()->getManifoldByIndexInternal(i);
    int numContacts = contactManifold->getNumContacts();
    for (int j=0;j<numContacts;j++)
    {
        btManifoldPoint& pt = contactManifold->getContactPoint(j);

        printf("%f\n", pt.getAppliedImpulse()); // log to see the variation range of getAppliedImpulse and to chose the appropriate impulseThreshold
        if (pt.getAppliedImpulse() > impulseThreshold)
        {
                // increase score or something
                break; // no more searching needed
        }
    }
}