Graphics Settings and Performance
Flight simulators are demanding applications. They can be tuned down to run smoothly on old laptops, or loaded up to bring a modern desktop to its knees. Performance is even more critical with virtual reality. For an optimal experience you'll want to spend some time balancing graphical quality, smoothness, and crispness. FlyInside is a demanding program, you'll want to make sure that your computer meets the specifications listed under Hardware Setup. If not, you'll need to use especially conservative graphical settings for an enjoyable experience.
Virtual reality tricks the user into believing they are in a virtual world. To do so, it needs to update the image the pilot sees, nearly instantaneously, as they turn their head. Any lag breaks the illusion, and can even induce nausea. Modern HMDs run at a steady 90fps, and anything lower is unusable. At the same time, HMDs introduce additional overhead over conventional graphics, in terms of stereo overhead, and the need for reduced latency. If your flight simulator is running at 70fps normally, it may only hit 35-50fps with FlyInside. You'll need to adjust your graphics settings accordingly.
Flight simulators rarely achieve 90fps, certainly not with any consistency. FlyInside bridges the gap using asynchronous timewarp. Even if your flight simulator is only running at 30fps, FlyInside takes each image from the simulator and displays it multiple times, rotating it to account for head movement. This way head rotation still feels smooth, and VR still feels good, even at lower frame-rates.
Once you are loaded into an aircraft cockpit in FlyInside, press your interact key. You'll see the FlyInside Tag appear, which shows FPS in a format such as "FPS: 55/90". The first number is your simulator frame-rate, while the second number is the asynchronous timewarp frame-rate.
Asynchronous Timewarp FPS
FlyInside tries to keep asynchronous timewarp running at a steady 90 fps (or 75 fps for the Oculus DK2). If this number drops lower you'll experience judder, a very uncomfortable sensation. While asynchronous timewarp is generally robust, certain conditions can still result in judder.
- Let's say you feel judder, and see a frame-rate like "FPS: 25/60". This is a case of computer overload. Your simulator is overloaded and running slowly, and is also not leaving enough room for asynchronous timewarp to breath. You'll need to turn down simulator or graphics settings as described below.
- On the other hand, you may feel judder, but see a frame-rate like "FPS: 110/72". In this case, the simulator is running very efficiently, so efficiently that it is starving asynchronous timewarp. Turning up graphics settings may actually help asynchronous timewarp and make VR feel smoother. You can also set a frame-rate limit from your flight simulator's settings as described below.
While asynchronous timewarp is responsible for keeping VR smooth and nausea at bay, your flight simulator's FPS effects the flight itself. A simulator FPS of >50 will feel quite smooth, while <30 will feel annoyingly laggy. It's up to you to find the frame-rate vs graphics balance you're happiest with though.
A low simulator frame-rate means that your mouse, Vive controllers, and Leap Motion will also run at a lower frame-rate. Input will not feel as smooth in general. If input feels uncomfortable or slow, try increasing your frame-rate.
A low simulator frame-rate also effects the smoothness of flight. Rolls will feel jerky, and close to the ground, motion will not appear smooth either.
Finally, a low simulator frame-rate can effect the feeling of VR immersion. While asynchronous timewarp keeps head rotation feeling smooth, it can also introduce artifacts. Turning your head quickly will result in black appearing at the edges of your vision where FlyInside cannot fill in the gaps. Asynchronous timewarp also doesn't help with translational movement. Turning your head left and right will be smooth, but a low frame-rate makes moving your head from left to right feel jerky. If you notice an annoying amount of black at the edges of your vision, or positional head movement is uncomfortable, increasing your simulator frame-rate will help!
It's really important to note that everyone has a different preference with simulator frame-rate. Some find the smoothness of flight and head movement to be a top priority, and run their simulator at 70+ fps, at the expense of graphics. Others barely feel a low frame-rate, and run at 25fps with hundreds of buildings and detailed aircraft.
To tune FlyInside a three-step process is recommended
- Turn down all graphics settings until you have performance you are really happy with
- Turn up resolution until you have crispness you are really happy with
- Turn up the graphical settings you care about most, until you have a good balance between smoothness, crispness, and visual fidelity