Quaternion.Euler(x,y,z)返回一个绕x轴旋转x度再绕y轴旋转y度再绕z轴旋转z度的Quaternion,因此Quaternion.Euler(0,90,0)返回一个绕y轴旋转90度的旋转操作.

Quaternion作用于Vector3的右乘操作（*）返回一个将向量做旋转操作后的向量.

因此Quaternion.Euler(0,90,0)*Vector3(0.0,0.0,-10)表示将向量Vector3(0.0,0.0,-10)做绕y轴90度旋转后的结果.因该等于Vector3(-10,0,0).

参考：

https://blog.csdn.net/u011574810/article/details/53421073

http://zuoye.baidu.com/question/8e9b4285b221904e0209da0fa54f2d79.html

http://wiki.ros.org/kdl/Tutorials/Frame%20transformations%20%28Python%29