How do VR systems work?

[Modred189]

So, you have a single scene to show in two slightly different ways in the headset to give a stereoscopic effect.
Does the scene have to be rendered twice? Or, is it rendered once, and the game inserts two "cameras," one for each image?
Do different setting have to be applied more than once? I.e., AA/AF/HBAO etc. Is it applied once to a scene and then split between cameras, or is each scene generated, and then these run on the view of each camera?

All the articles I've been reading about the large overhead for VR seem to indicate a lot is being duplicated...

 

[USMCGrunt]

From what I've read, instead of a single viewpoint being rendered there are two. Some things are duplicated but others like AA are done in a single pass.

 

[The_Oasis]

So, you have a single scene to show in two slightly different ways in the headset to give a stereoscopic effect.
Does the scene have to be rendered twice? Or, is it rendered once, and the game inserts two "cameras," one for each image?
Do different setting have to be applied more than once? I.e., AA/AF/HBAO etc. Is it applied once to a scene and then split between cameras, or is each scene generated, and then these run on the view of each camera?

All the articles I've been reading about the large overhead for VR seem to indicate a lot is being duplicated...

Hi, Modred! VR is some super cool stuff, and obviously there's a ton of work that goes into it.

You're right about the two camera point thing, but remember that that is going to require two separate renders, since they are both different images. It's not doubly as difficult, though: remember that the resolution of each of the two camerapoints isn't going to be the same as you'd render on a proper display.

That all sounds well and good, but there are also some other fun factors. Refresh rate makes a lot more of a difference, for example. Temporal Aliasing is a term for how having a high number of frames that will all be from *slightly* different perspectives (just from your head moving as it does) will give this appearance to the viewer of more than just the default resolution, since you're technically getting more views of it from different points. This is specifically to help with Screen-Door Effect, which for now is still an issue.

If you can, get Google Cardboard on your phone, even if you don't have a cardboard, and try run a game. Notice how it'll prevent those two different views to look at.

If you want more info, please ask!