As far as I know software IPD don´t suppose any performance cost. I’ve been playing a lot with it and with a game with PP needed, like PC2, if we disable PP we get a picture similar to this;
(both eyes represented, FOV mask, I’ve inclined both pictures as in canted displays and I’ve separate them)
If we set Software IPD to -5 we get a picture similar to this one;
Setting it to -10 we get a picture similar to this;
I think if we could set it to -15 or so, the picture would be like this;
The center of the picture is almost perfect, if we look at both sides we see some double vision caused by the inclination of each screen but I think if our eyes focuses on the tree (for example) it would be easy to them to create a unique 3d picture. It should work with the center too.
Sure it will not be perfect but with a gain of 40% in performance, disabling PP I think our brain would do the trick. It must
(I think this “trick” is only feasible with racing games)