Wirebook › Glossary › Screen tearing
What is screen tearing (and how do you fix it)?
In one sentence: A line across the picture where the top shows one frame and the bottom the next, because the screen swapped pictures halfway through drawing.
A little more
A screen doesn't change its whole picture at once. It paints it from top to bottom during every refresh. If the game hands over a new frame while the screen is partway down, and nothing makes it wait, the rest of that refresh is painted from the new frame. The top half then shows one moment and the bottom half a slightly later one, and anything moving sideways is cut and shifted along a line.
Tearing is easiest to see when the camera turns quickly and the frame rate doesn't match the refresh rate. V-Sync stops it by only swapping frames between refreshes, at the cost of some judder and delay when the game can't keep up. VRR (G-Sync, FreeSync, HDMI VRR) stops it by making the screen refresh when each frame is ready, which is usually the best of both.
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