Help implementing either of these two radial distortion shaders.

Hello,
I'm working on an augmented reality project using the HTC Vive and I have recently learned about radial distortion. While looking into free solutions in the form of shaders to resolve this issue I came across http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter40.html (Example 40-1) and http://willsteptoe.com/post/67401705548/ar-rift-aligning-tracking-and-video-spaces-part (image at the bottom of the screen).

As this is my first time working with shaders, any help on how to implement either of these two would be greatly appreciated.

Thank you in advance.

Edit: https://github.com/googlevr/gvr-uni...ource/Shaders/SolidTextureUndistortion.shader
also just found this shader

 

I would recommend this:
http://www.alanzucconi.com/2015/06/10/a-gentle-introduction-to-shaders-in-unity3d/