Sure you have to render twice, but that’s the same with box, spherical, and screen-space reflections and yet they all work in VR too!
I’m probably beating a dead horse, and if this post gets ignored so be it, but planar reflections are something I’ve been looking forward to for a long while. I can indeed get under frame with using them in VR, unless the way they are now (lagging behind the rest of the scene) is the reason that they are rendering with a lower .gpu cost (in which case the rest of this post is kind of redundant).
I did some tests as the planar reflections are now in Preview 5, if there looks to be a problem with my methodology please let me know! My test scene has 3 dynamic shadow casting lights, all the primitives you can see, and two Vive controllers which both total about 30,000 triangles. Screenshots and profiling was done within the HTC Vive with a screen percentage of 140%. On the left I tried to emulate accurate reflections (reflection of environment with a box refl capture and reflection of local objects with SSR) In the middle, no reflections. On the right, only planar reflections at 40% screen space.
No reflections: 5.94
In conclusion, planar reflections are the most expensive, but they’re the only thing that actually comes close to emulating realistic reflections on a flat surface (and they look amazing). Unless I’m missing something, planar reflections not being performant in VR isn’t a good reason for their lack of VR compatibility. I only GPU profiled, I don’t know how the CPU compares but I imagine it increases drawcalls with planar reflections too.
http://i.imgur.com/ebnIF5At.jpg http://i.imgur.com/WvC1ze8t.jpg http://i.imgur.com/786hU09t.jpg