三维投影变换

周末动手做了几个投影转换，实现了 Sphere / Fisheye / Stereographic / Stereographic Fisheye 投影转换：
Sphere投影：

sphere

Fisheye投影(fullframe)：

fullframe

Stereographic投影(北极视点，视角约72度)：

stereographic 放个人进来不好看 放个人进来-_-

Stereographic鱼眼投影Preview(北极视点)：

stereographic_fisheye

参考资料：
https://wiki.panotools.org/Fisheye_Projection
http://hugin.sourceforge.net/docs/manual/Stereographic_Projection.html
https://wiki.panotools.org/Unusual_remappings#Little_planet
https://en.wikipedia.org/wiki/Stereographic_projection