Performance issue with complex QGraphicsScene

[wysota]

I can suggest a couple of things to try:
1. enable caching for items (as suggested by my preposter but with ItemCoordinateCache)
2. set ItemHasNoContents flag on all items that paint nothing
3. set "interactive" property of the view to false if you don't need your scene to be clickable
4. make shapes as simple as you can, if you scale use the level of detail information to avoid painting things that can't be noticed by the user
5. make use of drawBackground() and drawForeground() instead of having items that cover the whole scene
6. avoid clipping
7. try using the raster engine instead of OpenGL.