書中第二章講創建一個場景節點時，說左右手坐標系：
The names left-and right-handed are based on the fact that the orientation of the axis can be reconstructed using the left and right hand. The thumb is the x-axis, the index finger the y-axis, and the middle finger the z-axis. We need to hold our hands so that we have a ninety-degree angle between thumb and index finger and also between middle and index finger. When using the right hand, we get a right-handed coordination system. When using the left hand, we get the left-handed version.
【 左手和右手坐標系名字的由來是基於他們主軸方向的不同，方向是左手和右手來決定創建的。大拇指是X軸，食指是Y軸，而中指是Z軸。我們需要張開手使大拇指，食指和中指之間保持90度角。當使用右手時，我們就可以得到一個右手坐標系。當使用左手時，我們就可以得到一個左手坐標系】
說的很妙，我也就知道了為什么是分左右手的了。保持姿勢左手沒法逆時針，保持姿勢右手沒法順時針。