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GH3PC: Disabled VSync Observations and Explanations

 
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ExileLord  





Joined: 11 Sep 2007
Posts: 440
Location: Wisconsin

PostPosted: Tue Sep 08, 2009 5:38 pm    Post subject: GH3PC: Disabled VSync Observations and Explanations Reply with quote

I just figured I'd write this because I didn't really want to post a video tutorial that much as I wouldn't be able to cover everything in that as well but I may eventually.

Rundown of VSync

Vsync is by default, on in GH3PC and is one of the few pc games that does not have an option to disable vsync and 3rd party software is required to do so. I'll give a rough explanation of what vsync is.

Monitors, television sets, and almost every similar form of display has a property called the refresh rate which is measured in Hz. The refresh rate measures how many times the display can put a completely new image on the screen in a second. A monitor with a refresh rate of 60Hz can put a completely new image on the screen sixty times in a second.

In a game, there is usually a logic step and rendering step which are distinct from each other. The logic step which includes movement and similar runs at a fixed speed. The rendering step will typically run as fast as it can. Each time it completes a drawing, it will swap the one on screen with it. However a problem arises from this as it is not swapping images in sync with the monitor's refresh rate. Some images will be swapped while the monitor is swapping an image resulting in a shearing effect with the newer image on the bottom and the older one on the top. I could go into this farther but that should be more than enough info.

From this it would seem that VSync would be wanted naturally. However a problem commonly seen from VSync is the appearance of input lag which I have seen in many games, the most severe being Fallout 3 and Guitar Hero 3 PC. While in Fallout, it may have been an annoyance, the input lag in Guitar Hero 3 makes the game unplayable. The lag comes from the consequence of the game rendering before the monitor is ready. While the game is already on the next logical frame with corresponding image ready, the monitor is telling the game it isn't ready for it yet and may still be putting the last frame on the screen.

Disabling VSync is the only way Guitar Hero 3 becomes playable for me. Personally, I think an oversight this large is incredibly bullshit but that's what I've come to expect from Aspyr.

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Now, there are some bugs that arise as a result of disabling vsync and I will try to explain them. As I told you before, most games have a distinct logic step and a rendering step. In console games however, most games are running at a fixed speed, 25fps, 30fps, 60fps, etc. Because of this, the logic and rendering steps may bleed into each other or may not be separate at all. Guitar Hero 3's bleed into each other resulting in a few irritating side effects.

There are a few things that will remain constant in Guitar Hero 3 no matter how fast or slow the game is running. 3D animations, music, fretboards, and most other items will function normally. Some of the items that have strange effects are 2D animations, physics, and whammy which are tied to individual frames.

Side Effects
One of the most obvious things that happens is the disappearance of the flames that appear when hitting notes. The 2D animation for flames (and I'm sure others) works in a strange way. The animation proceeds at a fixed speed based on time rather than frames but stops when after a certain frame is reached.


Normally, running at 60fps, the animation would stop right after the game's seventh frame. By this time the flame will reached its seventh frame because ~100-116ms will have elapsed.However, if the game is running at say, 300fps which is common on a high end computer, by the time the game's seventh frame is reached, only 20-23.2ms will have elapsed in comparison. The flame will only be on its second frame of animation. The game will then tell the flame to stop animating because it will assume the animation has finished. This is a relatively insignificant bug but another more significant one comes from whammying.

When the game is running faster than normal, players will have to whammy faster than normal in order to get star power. The sustains will stay blue (60/FPS)% as long as normal. When getting to higher speeds, 300+fps, it becomes near impossible to fully whammy a note. Most players will run into trouble at around 150fps.

There are other oddities that result from this but I really do not want to bother explaining them all as this took long enough to write as it is. I may have made a few errors or explained something incorrectly but I think it is still informative to a degree.

All in all I wanted to dispel the myth that disabling flames increased performance when in reality, it was a side effect of a far more significant change. There's no in game option you can set to remove flames. I may edit this later to make it more clear but I think this is enough for now.
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Rapstah  





Joined: 01 May 2008
Posts: 868

PostPosted: Tue Sep 08, 2009 6:00 pm    Post subject: Reply with quote

Oh shit, so THAT'S why whammying bugged out. Most of this isn't Aspyr's fault by the way, they were given console-based code by Neversoft and that stuff is coded never to run below or above 60 FPS.
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eydee  





Joined: 24 Jul 2008
Posts: 56

PostPosted: Wed Sep 09, 2009 9:06 pm    Post subject: Reply with quote

It's worth to mention that loading a saved game (profile) on startup usually fails if the fps is greater than 60. In that case, manual loading is possible. This also happens if vsync is enabled but the monitor refresh rate is above 60.
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ExileLord  





Joined: 11 Sep 2007
Posts: 440
Location: Wisconsin

PostPosted: Thu Sep 10, 2009 11:04 pm    Post subject: Reply with quote

Rapstah wrote:
Oh shit, so THAT'S why whammying bugged out. Most of this isn't Aspyr's fault by the way, they were given console-based code by Neversoft and that stuff is coded never to run below or above 60 FPS.

Most pc ports include a vsync option. Since vsync creates a near unplayable game due to input lag, I see this as a major failure of Aspyr. I mean, it is a rhythm game. I could rant about Aspyr for a lot more but I won't.

In addition, even with vsync, some monitors have refresh rates at around 200Hz which would result in the problems noted above.

eydee wrote:
It's worth to mention that loading a saved game (profile) on startup usually fails if the fps is greater than 60. In that case, manual loading is possible. This also happens if vsync is enabled but the monitor refresh rate is above 60.

Odd, my fps in the menus is over 1000 and I never have this. More input on this would be needed.
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Auriscope  





Joined: 29 Nov 2007
Posts: 1402

PostPosted: Thu Sep 17, 2009 8:20 pm    Post subject: Reply with quote

You may want to mention that disabling vsync fucks up the video calibration tool pretty badly too. The notes will come down as if you had hyperspeed 10 enabled and you will get wildly high numbers.
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snelliot  





Joined: 03 Jan 2015
Posts: 1

PostPosted: Sat Feb 14, 2015 4:47 pm    Post subject: Playable how? Reply with quote

So I was doing fine with my GH3PC, but found that a lot of players had turned V-SYNC off so I decided to do the same. However, doing this made the game unplayable for me. When I measured the frame rate, it was well above 1000fps which I thought would be beneficial. Yet, I find it hard to hit a single note, but yet I can hit various trills and stuff on 60fps, why is this?
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plumato  





Joined: 14 Dec 2008
Posts: 79
Location: Richmond, VA

PostPosted: Sun Feb 22, 2015 9:58 am    Post subject: Re: Playable how? Reply with quote

snelliot wrote:
So I was doing fine with my GH3PC, but found that a lot of players had turned V-SYNC off so I decided to do the same. However, doing this made the game unplayable for me. When I measured the frame rate, it was well above 1000fps which I thought would be beneficial. Yet, I find it hard to hit a single note, but yet I can hit various trills and stuff on 60fps, why is this?


You need to spam!!!!!

Jk, but I've never seen anyone not be able to hit notes with vsunc off (which is why I mentioned spam) considering it makes the hitboxes EXTREMELY huge, and generous. It's probably just something to get used to?
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