osg通过圆柱拖拽器旋转获取旋转值

osg中可以通过拖拽器来获取旋转值。具体步骤如下：

1. 创建一个圆柱拖拽器，设置其位置和大小：

osg::ref_ptr<osgManipulator::CylinderDragger> dragger = new osgManipulator::CylinderDragger();
dragger->setupDefaultGeometry();
dragger->setMatrix(osg::Matrix::translate(0,0,0));

2. 将拖拽器添加到场景中：

osg::ref_ptr<osg::Group> root = new osg::Group();
root->addChild(dragger.get());

3. 设置拖拽器的回调函数，获取旋转值：

class MyDraggerCallback : public osgManipulator::DraggerCallback
{
public:
    MyDraggerCallback() : _startRotation(osg::Quat()), _currentRotation(osg::Quat()) {}

    virtual bool receive(const osgManipulator::MotionCommand& command)
    {
        osgManipulator::MotionCommand::EventType eventType = command.getEventType();

        if (eventType == osgManipulator::MotionCommand::START_DRAG)
        {
            _startRotation = _currentRotation;
        }
        else if (eventType == osgManipulator::MotionCommand::DRAG)
        {
            osg::Quat rotation;
            osg::Vec3 axis;
            float angle;

            osg::Matrix matrix = command.getWorldToLocal().getRotate();
            matrix.get(rotation);
            rotation.getRotate(angle, axis);

            _currentRotation = _startRotation * rotation;

            osg::Vec3 euler = _currentRotation.asEuler();
            float x = osg::RadiansToDegrees(euler.x());
            float y = osg::RadiansToDegrees(euler.y());
            float z = osg::RadiansToDegrees(euler.z());

            std::cout << "Rotation: " << x << ", " << y << ", " << z << std::endl;
        }

        return true;
    }

protected:
    osg::Quat _startRotation;
    osg::Quat _currentRotation;
};

dragger->addDraggerCallback(new MyDraggerCallback());

在回调函数中，可以通过获取拖拽器的变换矩阵，计算出当前的旋转值，并将其输出。