Comment by MindSpunk
13 hours ago
Most games haven't rendered directly into the "screen buffer" for 15-20 years.
Vast majority of titles use deferred rendering, and lighting is done off screen too. Usually the only thing done to the "screen buffer" is a final post-process pass or a copy.
Deferred renderers work differently from compositors. They still build up the entire displayed frame in screen space, except they dont write into a color buffer like directly, but produce a bunch or intermediate buffers, called G-buffers. Then they have a postprocess pass when they resolve these buffers into the final image.
This is called 'compositing' but its similar in name only. It's a fairly efficient process where each color pixel is produced by reading these buffer targets and producing a final color in a shader.
This is entirely different from what composited apps do, where they build up the app's background into a texture, and push that onto the screen, with potentially multiple screen's worth of windows living in memory. This would be equivalent in video game terms to rendering every character and object in the level as 'stickers' and then making the final image of these cutouts, which would consume tons of RAM uselessly, and would force us to render crazy amounts of detail that would never get shown.
It's one possible rendering pipeline. Is it really most games?
Regardless, video games normally update the entire screen (or window) every frame, because the screen is so dynamic. This is unlike Microsoft Excel which has a mostly static screen. Building Excel as if it's a video game is going to waste resources.