Slight, but noticeable, screen lag when using VSync

Unity Engine
1

In some of my scenes, framerates are pretty good, in the 150-200 FPS range. But since my monitor is only 60hz, this results in very noticeable tearing. So for this reason, I usually use VSync. However, I notice just the slightest sense of “lag”, or sluggishness when looking around with the mouse when VSync is enabled. It’s subtle, but I feel the slightest amount of motion sickness when VSync is enabled compared to when it’s off.

I’m using Time.deltaTime in my mouse-movement script, and I’m using Input.GetAxis() within Update() to monitor for mouse movement. So I believe mouse look should be independent of framerate. I was wondering if this sense of lag was just a normal side-effect of VSync, or if this isn’t expected behavior and I have a bug?

2

I’m experiencing the same on my Mac. (I just released a game and the players complained the control is sluggish)

It’s definitely a bug. It only occurs in standalone player but not in the editor. And there’s a huge lag if the framerate is lower like 30fps. If you turn vsync off, the lag is not there even when the framerate stays the same.

Unity definitely needs to fix it soon. It makes any action games by Unity basically unplayable with vsync on.

EDIT: maybe it is the maxQueuedFrames setting that generates the lag? In editor maybe this value is always working as 0 and in the build it’s something like 2 or 3 so there’s a noticeable lag?

EDIT: confirmed setting maxQueuedFrames to 0 doesn’t fix it. Should be a bug.

3

I’ll have to poke around with this a bit more to convince myself whether it’s present in a build but not in the Editor. Or whether this is the result is double or triple buffering in a build, with less intense buffering in the Editor.

4

I’ve found myself that not using deltaTime produces much better results in this case.
Try removing it, mouse inputs should become way more responsive. (Might need to tweak sensitivity values though)

Its fine for the mouse inputs to be device dependant.
Sensitivity settings usually implemented for the user to figure out what value is better for them.

5

Not sure your problem is the same, but have a look here for some lengthy discussions with several workarounds presented: Time.deltaTime Not Constant: VSync CameraFollow and Jitter