at the Game Developers Conference this week announced a new frame
capture analysis tool for virtual reality. Dubbed FCAT VR, the utility
is designed to help VR developers, reviewers and enthusiasts analyze the
quality and performance of a virtual reality experience.
benchmark utilities aren’t all that practical when it comes to virtual
reality. Zvi Greenstein, general manager of Nvidia’s GeForce team who
also leads business development for VR at the company, notes in a recent
that traditional measurement tools like FRAPS only measure what’s
happening on the desktop monitor instead of what’s happening on the VR
In other words, they focus squarely on frame rate and
don’t take other important metrics into account like latency, stutter
and hitching – all of which can have a big impact on the virtual reality
experience. If stutter and latency fall below a certain threshold, for
example, they can cause motion sickness – not fun.
FCAT VR, which
supports the Oculus Rift and HTC Vive, is said to provide a
comprehensive performance measurement for frame time and stutter on the
headset without requiring special external capture equipment.
The tool captures four key performance metrics:
- Frame Time
— Since FCAT VR provides detailed timing, it’s possible to measure the
time it takes to render each frame. The lower the frame time, the more
likely it is that the app will maintain a frame rate of 90 frames per
second needed for a quality VR experience. Measurement of frame time
also allows an understanding of the PC’s performance headroom above the
90 fps VSync cap employed by VR headsets.
- Dropped Frames
— Whenever the frame rendered by the VR game arrives too late for the
headset to display, a frame drop occurs. It causes the game to stutter
and increases the perceived latency which can result in discomfort.
- Warp Misses
— A warp miss occurs whenever the runtime fails to produce a new frame
(or a re-projected frame) in the current refresh interval. The user
experiences this miss as a significant stutter.
- Synthesized Frames
— Asynchronous Spacewarp (ASW) is a process that applies animation
detection from previously rendered frames to synthesize a new, predicted
frame. If FCAT VR detects a lot of ASW frames, we know a system is
struggling to keep up with the demands of the game. A synthesized frame
is better than a dropped frame, but isn’t as good as a rendered frame.
Nvidia’s new utility should be available to download by mid-March.