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Input Lag on Smart Phone VR

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100% VR noob here.

In the generic VR reviews I never see any mention of input lag. I heard high input lag makes you sick.
What would be the best case scenario with Smart Phone VR;
Which smart phone and smart phone VR system would provide the lowest input lag?
How does that compare to the dedicated VR headsets?

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Not sure specifically about the phone VR.

With the headsets people get quite angry when framerates drop below about 90 fps.  Most people don't report any motion sickness until the framerate drops below around 60, so keep that how you may.

Games always have lag between the simulation and what you experience.  At the very least you've got the buffer of what you see, the buffer of what is being drawn, and the simulation step that handles the current controller input.  Triple-buffered games add another buffer in there. Some older hardware (like the PS2) have more steps that involve yet another frame delay.

Couple it with the time it takes to physically display stuff, and the soonest a game can possibly show a visible response to a player's input is around 50 milliseconds. That's your minimum visual lag.  That is one reason audio cues are used too, since audio can usually be mixed in milliseconds after processing the update, so around 10-20 milliseconds after input.

 

 

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Thanks for the reply frob.

I stumbled upon a talk Carmack did. Video blew my mind, especially considering what he said he's working on near the end of it. So if you ignore cell phone VR and everything that we've used/done. 10-20ms is the sweet spot per the video. Is there any setup or proof of concept that gives you close to 15ms?

Edited by blitzin4
new info

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Yeah, he talks about the somewhat hidden aspect here, saying many games had the frames as described above, commonly around 3-4 visual frames.  But he isn't talking about the same type of input lag from games, he's talking mostly about video being processed.

I like how he described "some of these are my fault..." Again you've got the graphics frame on the screen, you've got the back buffer being rendered to wait for that is shown one frame out, you have the processing of the simulator that will be shown two frames out, and you've got input and events being generated and accumulated that will show up three frames out.  

If your game is running at 30FPS like some games do, that's 100 milliseconds at best. If you're running around 60FPS that's around 50 milliseconds at best.  If you're running at 75FPS that's 40 milliseconds. If you're running at 90FPS that's 30 milliseconds. 

It is certainly possible to remove some of that. You can remove vsync to take out about a quarter or half frame on some games. You can potentially change the input so you're not looking for button events, but that only works for some games since a quick button bump won't get picked up by that process.  It is quite hard to take it less than those numbers above.

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