Nuke STmap and how to use it inside engine

Hello ,
I have a problem with Lens Distortions maps inside engine. I will try to explain what i am doing.
I am getting video feed inside engine through MediaBundle and my BlackMagic card with SDI. I am comping it on top of CG background using Composure plugin. And to get better matching of two realities I need to undistort video feed or apply same distortion (redistort) my CG_Background render.
So I grabbed my camera , shooted distortion grid with my 50 mm lens , loaded in to the nuke , then I did lensdistortion solve and as result I got STmap’s for undistorting and redistorting. Since I want to apply distortion to my cg layer I rendered stmap for redistortion in EXR format. In Unreal inside my COMP material for composure I am adding this map to texturecoords and feeding it tu UV channel of my CG layer. And here the problem comes … How I understand in unreal you cannot use classical STmaps in linear space for this purpose , it should be in LMS space UV …
Can some one help me on using the STmap to apply distortion to my CG layer ?
Also I watched this video Getting Started with Composure | Live Training | Unreal Engine - YouTube
also downloaded this project , and I found out that they are using EXR file with redistortion map (looks like STmap but different witch I can’t render out) witch they applying to CG layer. They was talking about Nuke and distortion maps but I can’t understand how they got this kind of map…
I have this type of lense distortion (picture 1)
And in the video tutorial they use this type of lense distortion (picture 2)