Question about Virtual Reality

[Nasuti]

Does anyone have any idea why our fps is cut in half when we use the oculus rift?

I'm sure the computer must be doing some computation on the output to make it display properly on the rift, and that computation must dwarf the calculations needed to display it on the screen.. does anyone know more?

Is it just that single screen has been optimized while HMD has not? Or is there inherently more calculation that needs to be done to display it well on the rift?

Anyway, just curious. Any response is appreciated. Thanks!

 

[Jericho]

Does anyone have any idea why our fps is cut in half when we use the oculus rift?

I'm sure the computer must be doing some computation on the output to make it display properly on the rift, and that computation must dwarf the calculations needed to display it on the screen.. does anyone know more?

Is it just that single screen has been optimized while HMD has not? Or is there inherently more calculation that needs to be done to display it well on the rift?

Anyway, just curious. Any response is appreciated. Thanks!

I think there is a limitation of the USB interface on the tracking camera. Of course, that's not the only contributor, but I think its a significant one.
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The only evidence i have of this is my experience from several months ago, when I was experimenting playing without the tracking camera plugged in at all, and I went from a juddery mess to smooth operation.
The sacrifice is that you lose a portion of the head tracking ability as well as you lose a lot of color in the display (everything goes 'grey'ish').
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I'm not sur eif the tracking camera trick works anymore, or even has an impact at all these days... Thanks to all the hard work of the people on this forum in conjunction with the optimizations that FD has made my Rift runs smoothly now without the need to try and unplug the tracking camera.

 

[Spork]

Frame rates lower in VR because your video card is doing a lot more work.

In order to maintain a sharp image after the warping is done the game needs to be rendered at a larger resolution. Usually 25-50% higher. So although the final output is 1080p, the game is internally rendering at something more like 1440p. This is what the oculus quality slider does. Turn it down and it will lower the resolution the game is being rendered at and give higher frame rates, but the image will get blurry.

The game has to render 2 view points, one for each eye. So it has to calculate all the geometry, lighting and shadows twice. Turning shadows down can make a big difference. Ambient occlusion will destroy your frame rates. How well optimized that is depends on the engine and how FD do the rendering. Some games do each eye in a separate pass which is slow, but others have both view points rendered in a single pass.

If you're running vsync, dropping below the target frame rate will half it due to how vsync works. Nvidia's adaptive vsync avoids this problem.

 

[r00x]

Does anyone have any idea why our fps is cut in half when we use the oculus rift?

I'm sure the computer must be doing some computation on the output to make it display properly on the rift, and that computation must dwarf the calculations needed to display it on the screen.. does anyone know more?

Is it just that single screen has been optimized while HMD has not? Or is there inherently more calculation that needs to be done to display it well on the rift?

Anyway, just curious. Any response is appreciated. Thanks!

Spork has explained the issues quite well! You could also add, your system is having to process live video data from the Oculus camera, pick out the infrared LEDs in real time, identify them uniquely, and compute a result for the orientation and position of your headset in combination with data streamed from the Rift's onboard IMU. It also has to use that data to guess where your head is moving to next and try to make sure any video frames are adjusted such that by the time they reach your eyes they are aligned to reduce the appearance of latency (time warping). That's quite a bit of work as well, really.