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Is the framerate shown in the debug window meaningful?


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I've been having very severe framerate problems since 1.1.1 came out (see my comment on but #9488), and in the process I've discovered that the framerate reported (and graphed) on the "Performance" tab of the debug window (Alt-F12) seems to be completely meaningless.

In particular, the debug window reports an almost rock-steady 25.1 FPS with very occasional instantaneous spikes to faster speeds.  This is despite my usual frame rate being more like 15 FPS (I would estimate), and even when the frame rate drops to just 3 FPS (yes, so slow I could count 43 frames in 15s!)

Is the FPS count displayed in the debug window supposed to relate to the actual graphical frame rate, or is it measuring something else unrelated?

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3 hours ago, cpcallen said:

Is the FPS count displayed in the debug window supposed to relate to the actual graphical frame rate, or is it measuring something else unrelated?

Well, I think it was probably intended to be accurate but a flaw in how it is implemented means it actually displays the number of rendered frames per in-game second rather than per real second.  Basically it will bottom out at (1 / <max physics delta-time per frame>) fps, if the framerate is below this value then in-game time is stretched and the display just shows the limit.

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I'd say just use Fraps instead, pretty much the bog standard fps thingy:

http://www.fraps.com/download.php

1 hour ago, Padishar said:

Well, I think it was probably intended to be accurate but a flaw in how it is implemented means it actually displays the number of rendered frames per in-game second rather than per real second.  Basically it will bottom out at (1 / <max physics delta-time per frame>) fps, if the framerate is below this value then in-game time is stretched and the display just shows the limit.

So that explains why it sometimes just bottomed out.

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On 5/5/2016 at 10:54 PM, Padishar said:

Well, I think it was probably intended to be accurate but a flaw in how it is implemented means it actually displays the number of rendered frames per in-game second rather than per real second.  Basically it will bottom out at (1 / <max physics delta-time per frame>) fps, if the framerate is below this value then in-game time is stretched and the display just shows the limit.

Ah hah!  That makes much sense.

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