Render 2d Density graph with OpenGL

[Uwe]

With DEBUG_RENDER i get, renderImage QSize(489, 193) 15

Considering, that this only for 489x193 pixels ( 5% of the number of pixels in my test ) this doesn't sound that good - so it might be worth to do optimizations for your value() method.

On the other hand you wrote, that you run into trouble with 10Hz, what indicates, that updates take >= 100ms. But considering, that you have 2 plots we would have 30ms only.
So there are > 70ms you lose somewhere else !

Uwe