It’s well-known among virtual reality (VR) users that VR can be very hard on graphics cards. For PC VR a high-end, expensive graphics card is a requirement for most VR applications, so developers are often keen to hear about techniques that can reduce the load on a GPU and improve its performance, to improve the longevity of hardware. Thus we have Oculus new rendering technique, known as Stereo Shading Reprojection.
Usually for VR apps is it necessary to render images twice – once for the left eye and once for the right eye. The Stereo Shading Reprojection technique allows pixels to be rendered once, then reprojected to the other eye, to share the rendering cost over both eyes.
Due to the distance between human eyes, each eye sees things from a slightly different perspective, so one eye might see areas the other eye does not. In the case of using Stereo Shading Reprojection this can mean some pixels are visible that shouldn’t be. To compensate for this, the software needs to identify which pixels are valid and which are not, so the invalid areas can be masked out to avoid a ‘ghosting’ effect.
Oculus tested the technology in Unity using simple shaders and buffers, exaggerating the ‘pixel cost’ by using dynamic lighting and discovered a dramatic performance improvement when the reprojection was used. In pixel-shader heavy scenes, a 26% performance improvement was noted. The developers tested the techniques using a AMD R290 and GTX 1080 and observed similar improvements.
The code sample for direct download will be available via the Oculus site soon.
VRFocus will continue to report on new technology in use in VR and AR.