I was saying in a gaming thread but, it's really hard to tell how good g-sync is. That demo is, not surprisingly, absolutely best case scenario and very unrealistic.
The left hand video when zoomed out remember had no v-sync at all, which is a joke. LIkewise the pendulum is an unrealistic un-game like model. Imagine you're playing I dunno, Cod, or GTA and it would be one person moving across screen at the same pace all the time. Rarely if ever happens, say in gta people stop for traffic, cars stop and start. When you start having unpredictable movement is when low frame rate is an issue.
Think of a guy running at you in game, if he runs from a distance at the same speed for 20 seconds then if you drop 3 frames you essentially know where he is then anyway. If that guy was randomly changing direction as he ran at you(making it harder for you to shoot him) then if there is a delay and he's changed direction in between, the slow frame rate you'll still be shooting as he's say moving right, when he's already changed to move left.
Also the frame timing is dodgy, the adaptable frame rate was unrealistic, it was worst case scenario for v-sync(though it was turned off anyway for much of the demo) and best case for g-sync. at 60fps each frame is 16.67ms apart, when you move to 59fps the frame is 17ms apart or so, at 58fps is 17.3ms apart.
This whole frame timing thing over the past couple years is exactly that, equal times between frames.
But games generally don't move from 60fps to 45fps slowly as in that demo, which gave each drop in fps essentially a smooth change in frame time. In games you are banging along at 60fps, then boom... explosion and particles and it's instantly 20fps. That is going from 60fps and 16ms per frame to 50ms a frame. That is what stutter is, that WILL be visible with g-sync in games when the frame rate changes in a realistic manner in game and when the animation is of unpredictable things. On a 120hz screen in this scenario you have a frame refresh every 8ms, so in this particular scenario if the frame is only ready after 50ms, with vsync enabled this frame wouldn't be shown till 56ms later, on g-sync this would be shown 6ms earlier.... but that is hardly a lot. In other situations g-sync will show a frame 7ms earlier, others 0-1ms earlier. It will make incredibly little difference, refreshing the same image over and over on a 120hz monitor while g-sync doesn't "refresh" but still keeps up the same image for the same amount of time won't make any visible difference.
Thing is g-sync will(or should) never be worse than v-sync and at times will be MUCH better, but the most likely situation is 70-80% of the time g-sync will make minimal difference to v-sync. The problem is each and every dev said, this will encourage us to be less concerned with dips into low frame rates, so bigger explosions and more particle effects for instance. However that will simply increase the instances in which you dip from 60 to 20fps in an instant, and that will look cack on v-sync or g-sync.
The biggest problem with low frame rate is as above, when someone runs across the screen, changes direction and you have a delay seeing it, or you spin around and a 360' turn is split into 20 different images rather than 60, or 100, more frames gives a smoother transition as you turn. Low fps sucks balls, tearing is a minimal/non existent problem with v-sync/high frame rate. g-sync fixes some animation issues when and only when the conditions are perfect such as the pendulum demo AND slow change in frame rate... unfortunately that best case scenario will basically never happen, an improvement will almost certainly happen. But if you're running at 120fps dropping to 60fps in the lows, g-sync won't be helping at all.
The silly thing is it seems most perfectly suited to consoles where dev's really do target frame rate limits(i can't name a PC game which does the same).
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