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BSP index implementation

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  • E Offline
    E Offline
    ecir.hana
    wrote on last edited by
    #1

    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!

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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #2

      Hi,

      That's the kind of question you should rather ask on the "interest mailing list":http://lists.qt-project.org/mailman/listinfo/interest You'll find there Qt's developers/maintainers (this forum is more user oriented)

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      • E Offline
        E Offline
        ecir.hana
        wrote on last edited by
        #3

        Thanks for the hint, I just tried that.

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        • K Offline
          K Offline
          kenchan
          wrote on last edited by
          #4

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

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          • E Offline
            E Offline
            ecir.hana
            wrote on last edited by
            #5

            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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