The really exciting thing about working on VR at the moment is just how little we actually know. It really feels like the good old days of first working with a mouse and trying to figure out this brand new thing and having to learn how users interact with it. Some of my colleagues have been working on this stuff for years and certainly have learned a lot but since real mass-audience commercial products are not really on the market yet its early to think you actually have the answers.\\r\\n\\r\\nThere are tons of controversial topics at the moment- performance requirements, issues around making people sick, input, interactions, APIs, support for multiple hardware platforms, and more. I’ll try to touch on a couple of these things, but keep in mind that while it’s a subtle distinction these comments are a bit more \\"a few things we have learned\\" rather than \\"what we know\\". And even more importantly I’m reluctant to say \\"you need to do it this way\\" because people are still inventing great ways to make stuff work.\\r\\n\\r\\nHaving said that I’ll touch on some performance stuff. A bunch of people were working at Valve for years development experimental hardware to try to understand the basic characteristics of what a VR system needs to really create a solid comfortable sense of presence. Of course there are lots of caveats and I’ll go into the details of what I think comfortable means but for me that means you need a display that updates at 90 frames per second with really solid tracking so that as you move your head the photons that hit your eyes really correspond to what would normally be happening as you move your head in the real world.\\r\\n\\r\\nHitting that 90 fps can be quite a performance challenge. When I’m playing games on my normal monitor I tend to prioritize beautiful rendering over frame-rate. I play on my 30\\" monitor and crank up the quality settings and if the frame-rate ranges between 25fps to 50fps, fine. VR is a different beast- if you don’t hit 90fps consistently your users will feel sick. As they move the world won’t keep up with what the brain expects to see and for most people this can cause motion sickness which really ruins the experience. \\r\\n\\r\\nSo its critical that you hit 90fps. There are a bunch of techniques that game engines need to adopt to accomplish this since they traditionally have been designed to run at a fixed quality level with variable frame-rate. But there are also the questions about what hardware you need for this and its difficult to provide clear answers. Our demos at GDC all ran on a powerful gaming PC (although one that used normal parts) with a NVidia GTX 980 GPU. We wanted to show some high end experiences and preparing demos for an event like that doesn’t give you much time to optimize performance. But you could certainly run a bunch of great VR experiences on a machine with lower end parts. I guess the difficult part is just that its so hard to provide clear guidelines on what hardware you need given all the variables of the different kinds of content, how much optimization will happen before release and the need to hit that frame-rate with a lot of pixels consistently.\\r\\n\\r\\n