Qt raster engine vs OpenGL in QGraphicsView
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I am working on a scene/view representation of a scalable graph diagram. I am now doing performance tests with thousands of nodes and edges and I am puzzled with few things. Test with 10 000 movable nodes and 10 000 edges:
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Using OpenGL instead of native raster engine is actually worse (class QOpenGLWidget). With raster I can zoom out to see everything and while it stutters it is actually not that bad. With OpenGL I can barely zoom out to see everything before it starts dying badly.
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In neither OpenGL or Qt raster has antialiasing noticeable impact on performance. Which is strange because visually the difference is clearly noticeable and I would expect that with this amount of stuff being drawn I could get noticeable performance difference when disabled.
While the second point is more of a curiosity the first one seems important to me. If I understand correctly then Qt raster paint engine uses purely CPU while OpenGL should use hardware acceleration. So OpenGL should really be a lot better at this. However since it is slower/worse performance wise I would say that it is only being emulated through CPU and no graphics card is actually. Can I check that somehow from within the programme or set it? I seem not to be able to find the answer in the docs.
But of course maybe the raster IS actually better for drawing in QGraphicsView.
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Hi,
Things to check:
- What GPU do you have on your system ?
- OS ?
- Qt version ?
- GPU drivers ?
- Are you rendering too much objects on your scene ?
