Maybe I am wrong and do not see the things as they are.
But I will try to give you my point of view, so you will be able to explain me more clearly where I am wrong.
Let's speak for IL2Bos : My understanding is that the game request target render resolution and FOV, I think by using the steamVR layer. Then it computes video frames using vertex shader, pixel shaders, and other type of shaders .Pixel shader input are in the display coordinate system, that is for example going from 0 to 1280 for X and from 0 to 1440 for Y, if this resolution is given to game.
Then the Pimax rendering is called, and make things like deformation for lens and maybe scaling, color correction,....
So image computation is made either by game and by Pimax renderer.
But if you give a wrong ratio to game, then the image computed by it will be "stretched" at the end. That was the case with OSVR/SteamVR, before it was fixed : Horizontal res. was 2 time the good one, so at the end it introduced weird deformation in IL2 BoS.
Just for information this was also the case with old version of Piplay , here is a video made by a Pimax user on this problem: https://www.youtube.com/watch?time_continue=2&v=bSnBtFyQdaM At this time I was using my OSVR HDK2, we fall on the same problem.
So, as the ratio I can read in game or steamVR is roughly at the same level than the Pimax 4K screen, things are looking OK, except that there is still these black bars in middle of view. Previoulsy (as in the video) the ratio was really different of the screen resolution, so the image was streched...
What I do not understood, is that IL2 Bos did not report the same resolution that I see in steamVR.
So can you explain me where I am wrong (and also what makes the latest versions of Piplay fix the stretching shown in video), so I will not bother you anymore with stupid questions ?