Hello all,

With my old computer and CRT monitor, I always turned the vertical sync on. Now that I have a new one with TFT-LCD, I kept the vsync off and the fps limiter on 100. Playing LFS with a mouse and these settings works like a charm for me.

But the odd thing is that when I turn vsync on again (59HZ apparently for my iiyama ProLite E2410HDSD) it feels as if the mouse sensitivity changes! It's so noticeable that I doubt it is caused by the game state being 40 frames per second more.

Does anyone have a clue as to why turning only the vsync on would have such a great effect on the mouse control?

Thanks in advance,
kind regards,

Zosma

LFS gets your mouse input for each frame.

If your game runs at 100FPS you get 100 steering updates per second, if you limit it to 59 you are losing precision.

PS: I hope you understand me, it's not easy to explain

Quote from Whiskey :

LFS gets your mouse input for each frame.

If your game runs at 100FPS you get 100 steering updates per second, if you limit it to 59 you are losing precision.

PS: I hope you understand me, it's not easy to explain

That was a great explanation if u ask me. Also, i had no idea it worked like that, so thanks for the info!

what exactly is vsync?

Quote from logitekg25 :

what exactly is vsync?

http://en.wikipedia.org/wiki/Vsync

Example, vSync off ... the picture starts to split. Is not progressive. Is mostly visible only when the camera is moving fast. Some people dont even notice it.

how much of a strain is vsync on your computer?

Quote from logitekg25 :

how much of a strain is vsync on your computer?

I dont get it, not sure what "strain" means. Something like "stress"? If yes, then yeah. In games wich have heavy graphics, turn that off and u will get a fairly good amount of extra fps.

Quote from logitekg25 :

how much of a strain is vsync on your computer?

Depend on the game and your rig, experience my vary between users, for me there is no impact in LFS while in some other games there is a big difference.
Also there is curious effect if you set Vsync on in double buffered mode it will cut your fps. for example it will display only 60, 30, 20, 15, 10 means that if your fps is 45 it will be cut to 30 (Dont remember exactly how this thing work but more or less how i explained..I think :razz
Also

Quote from hazaky :

Example, vSync off ...

Example is pretty good in itself but it wont work like this in LFS unless you use track ir or free track.
This terrible looking result when image look like victim of the butcher split in pieces its noticeable mostly during panning.
Examples shooters, flight sims when you use head tracking device to look around cockpit and i think that's it.
In race games like LFS I think you wont notice it (Unless you use head tracking device but even then Vsync off doesn't automatically mean that image quality goes down, its differs from game to game and your rig)

<VSync explanation, kind of OT>
When graphics card renders a frame, it stores the result to a piece of memory called the "frame buffer". Frame buffer is then sent pixel by pixel to your screen which displays it's content.
Now assume that your screen has a refresh rate of 60Hz = it redraws itself every 1/60th second. If a game runs at 120 FPS, it means that the frame buffer is overwritten when your screen is exactly in the middle of the refresh cycle. One half of the resulting image will be from a different frame than the other one and this is what causes the so called "tearing".
VSync makes sure that the frame buffer can be updated only when the screen's refresh cycle has _just completed_. So if you enable VSync in the case I described above, graphics card will spend half the time idling because it will have no place where to store calculated image data.
When double buffering comes to the scene, situation is a bit more complicated and not easily explicable by words. The result is that with VSync you can get framerates like "refreshRate / X" where X is an integer. So if you're playing a game wich can run at 59 FPS but your screen has 60Hz RRate, you will get only 30 FPS.

It causes no extra load on your system so enabling it will not reduce your framerate itself. My personal opinion is that limitng FPS to your screen RRate is a better option. It might not eliminate tearing, but there is a good chance it will reduce it.
</ VSync>

Vsync should not affect mouse's motion in any way. LFS tried to update physics every 1/100th second regardless of the framerate. It's logical to assume that it reads the controls input at the same rate. Cap framerate to 60Hz and turn VSync off and see if the feeling of strange mouse motion persists.

Quote from Whiskey :

LFS gets your mouse input for each frame.

If your game runs at 100FPS you get 100 steering updates per second, if you limit it to 59 you are losing precision.

PS: I hope you understand me, it's not easy to explain

Ha... I had thought about this but thought it wouldn't be that noticeable. Well... I'm turning off vsync then because the tearing doesn't bother me as much as losing steering precision.

Thanks,
Zosma

Quote :

Vsync should not affect mouse's motion in any way. LFS tried to update physics every 1/100th second regardless of the framerate. It's logical to assume that it reads the controls input at the same rate. Cap framerate to 60Hz and turn VSync off and see if the feeling of strange mouse motion persists.

Mmm I just tried it with a cap at 58FPS and VSync off... it does indeed feel the same as when limited to 100FPS. So it's really only enabling VSync that makes the mouse motion feel strange.

Greets,
Zosma

@MadCatX: As you see, this is the second thread that condirms that FPS or VSync have an effect in user inputs. But, as you say, I can't understand why this works that way

Quote from Whiskey :

@MadCatX: As you see, this is the second thread that condirms that FPS or VSync have an effect in user inputs. But, as you say, I can't understand why this works that way

Actually thats easy.
Time of human reaction is pretty fast something around 0,2 sec i think.
Also average player move his mouse/steering wheel with great speed while playing.
While game plays with relatively small speed if compared with speed of human motion.
So when you move your mouse fast you can see effect on the screen at the same moment only if your fps is good around something around 50 fps so the computer can keep up with the speed of your motion and can reproduce it on the screen, if its lower for example 25 fps you move your hand and you notice that there is big delay because everything is slower on the screen because you moving your controller faster than computer can reproduce its movements to the screen.

Unfortunately my English sux big time, hope you get more or less what i wanted to say.

Yes, but internal LFS physics still runs at 100Hz, the FPS should only affect the monitor, not any input.

This is the thing we don't understand, but of course there must be a reason for that hehe

Scawen could help us out with this question.

Quote from Whiskey :

Yes, but internal LFS physics still runs at 100Hz, the FPS should only affect the monitor, not any input.

This is the thing we don't understand, but of course there must be a reason for that hehe

That is exactly what it is about. If your fps is lower than the physics engines' update rate, anything that happens in game gets to your senses with a delay. VSync only increases this effect because it defines exactly when the image on the screen can be refreshed. User input is not altered in any way.
If you get drunk, objetcs don't suddenly get blurry edges, it's just your brain being decieved by the high dose of ethanole. In this case your se/ses just get wrong info too, creating the confusion.