Bad graphics performance under KDE

Problem

When starting Flightgear under KDE, the graphics performance is very bad, i.e. low framerates, while running Flightgear in a different window manager shows better performance.

Reason

It is likely that "compositing" is activated. KDE includes a large number of various effects which use OpenGL. This degrades the performance of applications that use OpenGL heavily.

Solution

Disable compositing permanently or temporarily in the KDE settings, via the assigned hotkey (normally Shift + Alt + F12) or via a script.

Caveats

With compositing disabled, KDE desktop effects don't work anymore.

Example

This example by i4dnf deactivates compositing, starts Flightgear and reactivates compositing after Flightgear ended.

#!/bin/sh
qdbus org.kde.kwin /KWin toggleCompositing && /usr/games/bin/fgfs $@ && qdbus org.kde.kwin /KWin toggleCompositing

See also / related

• Forum post by i4dnf