![]() In a wireless PCVR split-rendering setup, the demands of the game may overwhelm the capabilities of the PC, causing the render and display rates to become mismatched. See below for the ideal scenario where the rendering and display rates match: PC frames available at HMD refresh rate. At 120 FPS, the application rendering must complete in less than 8ms. When the display rate of the XR device is 90 FPS, it leaves less than 11ms for the application rendering to complete. While similar to video frame interpolation, which produces an intermediate frame between a past and future frame, VR produces a future frame extrapolated from only the previously rendered frames. These techniques produce a new frame representing what the missing frame would have looked like had it been rendered, to prevent rendering a duplicated frame. ![]() Synchronous Space Warp (SSW) (the focus of this blog).There are several variations of Space Warp: Judder can be addressed using Space Warp – a technique that fills in missing frames. Example of judder in VR when the application render rate doesn’t match the display rate. When the render rate doesn’t match the display rate, frame judder can manifest itself as double images, ghosting, or blurring (see below). ![]() However, traditional ATW can only correct for head rotations and cannot account for game animations, controller motion, 6DoF movements (e.g., translation/walking in the scene), or game animations. It also ensures low-latency head movements are reflected on the display (aka low motion-to-photon latency), which is important for preventing cybersickness. One method to achieve this is Asynchronous Time Warp (ATW) which corrects for subtle differences in head rotations between the render and current pose. High-performance rendering happens when the application’s render rate matches the display’s hardware display refresh rate. Let’s take a closer look at how this works. This doubles the available PC render time and the effective encoder bitrate for PCVR-to-HMD streaming. Space Warp produces missing frames just-in-time on the HMD with no PC overhead, thus reducing PC-to-HMD bandwidth and stress on the encoder. We added Space Warp functionality to our Adreno Motion Engine which runs on all headsets powered by our Snapdragon XR2 and its Qualcomm Adreno GPU. Last year we collaborated with Guy Godin, creator of Virtual Desktop, to enhance PCVR rendering performance. ![]() Switch this setup to a wireless HMD, and the communications channel (e.g., Wi-Fi, 5G, etc.) must also be up to the task of real-time data transfer. This setup must contend with fluid controller and game movements, 6DoF animations, head movements, and two render passes (one per eye) at 90 to 120 FPS. A typical PCVR (PC and VR) setup comprises a PC connected to a head-mounted device (HMD) and a pair of hand-held controllers that must all function in real-time. Rendering in VR demands that hardware and applications maintain very high frame rates. Co-written by Jonathan Wicks and Sam Holmes ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |