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Old 06-24-2022, 10:41 PM
mg is offline mg
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Join Date: Jun 2022
Posts: 27

Variable mouse polling rate

Hello,

I've observed what feels like negative acceleration of the mouse input in a few Novalogic games.

However:
  • It seems highly dependent on the scene: sometimes it will happen, sometimes it will feel more pronounced than other times, sometimes it won't happen at all. Anecdotal evidence suggests the variability may correlate with the complexity of the scene being rendered.
  • Often the effect will be more pronounced when rotating in one direction as opposed to the other (e.g. flicking right may rotate wider than flicking left, while moving the mouse slowly typically results in a consistent angle in either direction -- the widest).
  • In some games, in a similar scene, anecdotal evidence suggests the effect may be more pronounced at higher resolutions.

I think I've felt it while playing through DF1 and DF2, but I don't remember exactly. I've done multiple tests in the helicopter scene at the start of the training quick mission in DFLW and I am certain the problem is present there. I've done further tests in DFTFD (shown below) and the problem is still there. I vaguely remember having the same problem in DFBHD (years back).

Demonstration. In this video, any time I reset the character direction to face south, I also lift my mouse to place it at the leftmost side of my pad. Any time I rotate right, I always move the mouse over the same distance (to the other end of the pad). As you can see, flicking quickly results in a shorter angle in game.

The only reference to the problem I could find is this post, but the suggested cause there is likely a red herring. Indeed I do not use dgVoodoo or any other type of wrapper.

Some other notes:
  • I do not remember this "way back in the day" when I played these games for the very first time. It's likely I wasn't paying attention to this at all then, but it may also be related to differing hardware capabilities.
  • The problem does not happen with any other non-Novalogic first-person game I run on the same system.
  • Continuously flicking left and right sometimes results in the viewport slowly panning down. This may be the same issue: even though I reset my mouse position after every flick, it's possible that I perform slight forward/backward movement with varying speed when I do that.
  • I am using modern hardware relative to the games release dates (9900KS/2080ti). I do not have any reason to believe it is faulty or insufficient.

From all these observations I tentatively conclude that the problem may be related to a variable polling rate of the mouse input, which may or may not be tied to the frame rate of the game simulation and/or the renderer (which may all be part of the same loop for all we know). Temporarily reduced frame rate could thus result in less inputs being considered (more inputs "skipped").

Has anyone else encountered this before? Does this little hypothesis feel right?

Any insights would be super-appreciated!

Last edited by mg; 06-25-2022 at 11:44 AM. Reason: Fix typo: fine -> find
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