OSG中的坐标系和OpenGL中的坐标系
OSG中采用四元数表示旋转：osg::Quat(angle to rotate, rotate around axis);
///***
///Q quaternion * P quaternion means that first conduct a rotation
P,Second conduct a rotation Q, means a fusion about two rotations with a
multiplication operation ///***
The osg coordinate definition as left-hand coordinate which is right-front-up(x-y-z) and the OpenGL coordinate definition also as left-hand coordinate which is right-up-behind(x-y-z), z axis is pointer to outside the screen The OSG default viewport is along down direction, so heading is rotate to be equal to the y positive direction, rotate axis is x axis
