On Windows platforms, Octave uses software rendering for the OpenGL graphics toolkits ("qt" and "fltk") by default. This is done to avoid rendering and printing issues due to imperfect OpenGL driver implementations for diverse graphic cards from different vendors. As a down-side, software rendering might be considerably slower than hardware accelerated rendering. To permanently switch back to hardware accelerated rendering with your graphic card drivers, rename the following file while Octave is closed:
octave-home\bin\opengl32.dll
where octave-home is the directory in which Octave is installed (the default is C:\Octave\Octave-version).
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https://octave.org/doc/interpreter/Hardware-vs_002e-Software-Rendering.html