contacts - 子弹物理 : contacts force/impulse

Question

我希望检测一个(球)何时接触另一个物体(目标)，并且我希望知道该接触的冲动。

我知道三种检测联系人的方法

gContactAddedCallback

或

    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
            }
        }
    }

或

检查线速度和角速度的变化。 (不清楚是否存在接触以及是什么物体导致了速度变化，是物体还是阻尼、重力还是某种力场。

<小时/>

我希望获得包含联系冲动的联系信息。我注意到一些接触在 1 帧模拟中得到解决，其他接触则需要 2 帧，并且脉冲要低两倍。 (我得到了调试代码。)如果我能完全冲动地收到 1 条联系通知，那就太完美了。

我列出的所有方法都无法提供该联系人的完整信息。有时当球飞近目标甚至没有接触目标时就会触发。

预期的实现方式是什么？

如果接触能量较高，此类信息可用于播放冲击声或启动一些动画。

Answer 1

此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
        }
    }
}