Comment on Why don't we have motion smoothing on current consoles?

jarfil@beehaw.org ⁨4⁩ ⁨days⁩ ago

• Boomkop3@reddthat.com ⁨3⁩ ⁨days⁩ ago

  It’s worse

  30fps

  • render frame 1 - 33ms
  • show frame 1
  • render frame 2 - 33ms
  • show frame 2
  • render frame 3 -33ms
  • show frame 3

  latency: 33ms

  30fps interpolated

  • render frame 1 - 33ms
  • render frame 2 -33ms
  • interpolate frame 1|2
  • show frame 1
  • start rendering frame 3…
  • wait 16ms
  • show frame 1|2
  • wait 16 ms
  • show frame 2
  • interpolate frame 2|3
  • start working on frame 4…
  • wait 16ms
  • show frame 2|3
  • wait 16 ms
  • show frame 3 -> this is a whole 33ms late!
  • …

  And that’s while ignoring the extra processing time of the interpolation and asynchronous workload. That’s so slow, that if you wiggle your joystick 15 times per second the image on the screen will be moving in the opposite direction

  source

  • jarfil@beehaw.org ⁨2⁩ ⁨days⁩ ago

    Hm… good point… but… let’s see, assuming full parallel processing:

    • […]
    • Frame -2 ready
    • Frame -1 ready
      • Show frame -2
      • Start interpolating -2|-1 (should take less than 16ms)
      • Start rendering Frame 0 (will take 33ms)
      • User input 0 (will be received in 20ms if wired)
    • Wait 16ms
      • Frame -2|-1 ready
    • Show Frame -2|-1
    • Wait 4ms
      • Process User input 0 (max 12ms to get into next frame)
      • User input 1 (will be received in 20ms if wired)
    • Wait 12ms
    • Frame 0 ready
      • Show Frame -1
      • Start interpolating -1|0 (should take less than 16ms)
      • Start rendering Frame 1 [includes User input 0] (will take 33ms)
    • Wait 8ms
      • Process User input 1 (…won’t make it into a frame before User input 2 is received)
      • User input 2 (will be received in 20ms if wired)
    • Wait 8ms
      • Frame -1|0 ready
    • Show Frame -1|0
    • Wait 12ms
      • Process User Input 1+2 (…will it take less than 4ms?)
    • Wait 4ms
    • Frame 1 ready [includes user input 0]
      • Show Frame 0
      • Start interpolating 0|1 (should take less than 16ms)
      • Start rendering Frame 2 [includes user input 1+2… maybe] (will take 33ms)
    • Wait 16ms
      • Frame 0|1 ready [includes partial user input 0]
    • Show Frame 0|1 [includes partial user input 0]
    • Wait 16ms
    • Frame 2 ready […hopefully includes user input 1+2]
      • Show Frame 1 [includes user input 0]
    • […]

    So…

    • From user input to partial display: 66ms
    • From user input to full display: 83ms
    • Some user inputs will be bundled up
    • Some user inputs will take some extra 33ms to get displayed

    Effectively, an input-to-render equivalent of between a blurry 15fps, and an abysmal 8.6fps.

    source

    • Boomkop3@reddthat.com ⁨2⁩ ⁨days⁩ ago

      You’ve just invented time travel.

      The basic flow is
      [user input -> render 33ms -> frame available]
      It is impossible to have a latency lower than this, a newer frame simply does not exist yet.

      But with interpolation you also need consistent time between frames. You can’t just present a new frame and the interpolated frame instantly after each other. First you present the interpolated frame, then you want half a frame and present the new frame it was interpolated to.

      So your minimum possible latency is 1.5 frames, or 33+16=59ms (which is horrible)

      One thing I wonder tho… could you use the motion vectors from the game engine that are available before a frame even exists?

      source

      • jarfil@beehaw.org ⁨2⁩ ⁨days⁩ ago

        You’ve just invented time travel.

        Oops, you’re right. Got carried away 😅

        could you use the motion vectors from the game engine that are available before a frame even exists?

        Hm… you mean like what video compression algorithms do? I don’t know of any game doing that, but it could be interesting to explore.

        source

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