Box2D的身體旋轉

Question

我有一個姿態recignizer，我需要旋轉體：

- (void) rotate:(UIGestureRecognizer*)recognizer node:(CCNode*)node 
{ 
    b2Body *body = (b2Body*)[node.parent userData]; 
    UIRotationGestureRecognizer* rotate = (UIRotationGestureRecognizer*)recognizer; 
    b2Vec2 pos = body->GetPosition(); 
    body->SetTransform(pos, (- rotate.rotation)); 

} 

offcorse，當我開始旋轉時，它從零角度開始。 * 但是如何從當前角度繼續旋轉？ *我不能只添加rotate.rotation tu當前角度：這種方法每一次都會調用，角度是從開始時的手勢開始計算的。跟蹤實際的當前角度（不anctive手勢的角度），將是一個非常艱鉅的任務，我認爲

Answer 1

我找到了解決辦法： 我檢查的手勢的狀態（有一個begining狀態）：

- (void) rotate:(UIGestureRecognizer*)recognizer node:(CCNode*)node 
{ 
    b2Body *body = (b2Body*)[node.parent userData]; 
    UIRotationGestureRecognizer* rotate = (UIRotationGestureRecognizer*)recognizer; 
    if (rotate.state == UIGestureRecognizerStateBegan) 
    { 
     baseAngle = body->GetAngle(); 
    } 
    b2Vec2 pos = body->GetPosition(); 
    body->SetTransform(pos, (baseAngle - rotate.rotation)); 

}