需要使用coco3d绕z轴移动

Question

在我的iOS应用程序中，我有一个用cocos3d创建的3D对象。 它在x和y轴周围正确移动。但它不想绕z移动！ 图片展示了它如何随着黑色箭头移动，以及它如何与红色箭头一起移动。

来自scene.m的代码

-(void) touchEvent: (uint) touchType at: (CGPoint) touchPoint
{
    switch (touchType) {
        case kCCTouchBegan:
            break;
        case kCCTouchMoved:
            [self rotateMainNodeFromSwipeAt: touchPoint];
            break;
        case kCCTouchEnded:
            break;
        default:
            break;
}

// For all event types, remember where the touchpoint was, for subsequent events.
_lastTouchEventPoint = touchPoint;
}
#define kSwipeScale 0.6
-(void) rotateMainNodeFromSwipeAt: (CGPoint) touchPoint
{
    CC3Camera *camera = self.activeCamera;

    // Get the direction and length of the movement since the last touch move event,
    // in 2D screen coordinates. The 2D rotation axis is perpendicular to this movement.
    CGPoint swipe2d = ccpSub(touchPoint, _lastTouchEventPoint);
    CGPoint axis2d = ccpPerp(swipe2d);

    // Project the 2D axis into a 3D axis by mapping the 2D X & Y screen coords
    // to the camera's rightDirection and upDirection, respectively.
    CC3Vector axis = CC3VectorAdd(CC3VectorScaleUniform(camera.rightDirection, axis2d.x),
                              CC3VectorScaleUniform(camera.upDirection, axis2d.y));

    //CC3Vector axis = CC3VectorScaleUniform(camera.upDirection, axis2d.y);

    GLfloat angle = ccpLength(swipe2d) * kSwipeScale;

    // Rotate the node under direct finger control, by directly rotating by the angle
    // and axis determined by the swipe.
    [self.modelNode rotateByAngle:angle aroundAxis:axis];
}

为什么它不想绕z轴移动？

Answer 1

您的意思是想围绕相机的Z轴旋转节点吗？如果是这样，您上面导出的axis（与CC3DemoMashUpScene中的代码相同）会使用相机的rightDirection和upDirection来创建根据定义，axis垂直于相机的Z轴。 rightDirection和upDirection定义了一个垂直于相机指向方向的平面，因此这些向量的任何线性组合都将产生一个位于该平面内的向量。

要围绕Z轴创建旋转，axis必须包含一些Z分量。相机的forwardDirection可以提供此Z轴组件。对于在相机的Z轴周围仅旋转 的非常简单的示例，请尝试将axis设置为：

CC3Vector axis = CC3VectorScaleUniform(cam.forwardDirection, axis2d.x);

或axis2d.x和axis2d.y的某种组合。