btRigidBody類主要用於剛體數據的計算。

在模擬剛體動畫過程中，可以使用btRigidBody類獲取所保存的剛體對象，進而控制剛體對象的旋轉和位移。進行剛體模擬計算需要經常用到此類。

API：http://bulletphysics.org/Bullet/BulletFull/classbtRigidBody.html

創建剛體對象

    btCollisionShape* colShape = new btBoxShape(btVector3(5, 5, 5));//創建一個基本幾何體

    /// Create Dynamic Objects
    btTransform startTransform;
    startTransform.setIdentity();
    btScalar mass(
 
1.f);

    //rigidbody is dynamic if and only if mass is non zero, otherwise static
    bool isDynamic = (mass != 0.f);

    btVector3 localInertia(0, 0, 0);
    if (isDynamic)
        colShape->calculateLocalInertia(mass, localInertia);

    startTransform.setOrigin(btVector3(2, 10, 0));//剛體初始位置

    //using motionstate is recommended, it provides interpolation capabilities, and only synchronizes ‘active‘ objects
 

    btDefaultMotionState* myMotionState = new btDefaultMotionState(startTransform);
    btRigidBody::btRigidBodyConstructionInfo rbInfo(mass, myMotionState, colShape, localInertia);
    btRigidBody* body = new btRigidBody(rbInfo);

    dynamicsWorld->addRigidBody(body);

從場景中獲取剛體對象

        btCollisionObject* obj = dynamicsWorld->getCollisionObjectArray()[i];//
 
i為場景中剛體對象的索引
        btRigidBody* body = btRigidBody::upcast(obj);

常用方法：

剛體質心坐標：

　　body->getCenterOfMassPosition();

獲取剛體四元數：

　　btQuaternion qua = body->getOrientation();

剛體旋轉矩陣：

　　btTransform trans;
　　body->getMotionState()->getWorldTransform(trans);
　　btMatrix3x3 matrix33 = trans.getBasis();

向剛體添加外力：

　　body->applyCentralForce(btVector3(2, 1, 0));

向剛體添加轉矩：

　　body->applyTorque(btVector3(0, 30, 0));

設置剛體變換：

　　btTransform trans;
　　trans.setIdentity();
　　trans.setOrigin(body->getCenterOfMassPosition() - dx);
　　body->setCenterOfMassTransform(trans);

剛體對象

【Bullet引擎】剛體類 —— btRigidBody