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BSP index implementation

  • Dear list!

    Please, could someone explain to me how the BSP index of QGraphicsScene works?

    Specifically, how is it possible that items return a list sorted by z-value? Is it a property of BSP index or are the items explicitly "z-sorted" after a the index narrows down the possible candidates?

    Also, if BSP is used with triangles, the slitting plate of a triangle might cut another triangle into halves. QGraphicsScene does not operate over triangles but, I presume, over minimum bounding rectangles. Where does the splitting plane cut through? Is it axis-aligned?

    Thanks a lot in advance!

  • Lifetime Qt Champion


    That's the kind of question you should rather ask on the "interest mailing list": You'll find there Qt's developers/maintainers (this forum is more user oriented)

  • Thanks for the hint, I just tried that.

  • By the way the QGraphicsScene is 2D so the z value is just a way to manipulate the draw order.

  • Yes, I know and that's exactly my point. Where/when are them items z-sorted? Are they always kept z-sorted? If I change a z-value, is the whole BSP rebuilt?

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