Polygon area

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This topic contains 3 replies, has 4 voices, and was last updated by  Nader Belal 2 months, 1 week ago.

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  • #18494

    Jože Marinko
    Participant

    I need to calculate area from polygon, which is defined with matrix points:
    x[i],y[i]…
    I found macro PolygonOperation, but result is wrong. In some cases smaller, in some cases even negative.

    My syntax is:

    for i=1 to segments
    put x[i],y[i]
    next i
    put x[1],y[1]
    call “PolygonOperations”,
    parameters opcode=6,
    srcPolygon1=2,
    result=1,
    returned_parameters _area

  • #18496

    Péter Baksa
    Participant

    Hi,

    Does it help if your polygon is regularized? Counterclockwise order of points, no self-intersection, no points on other edges.

    Currently we don’t have an universal solution for area calculation in the ARCHICAD Library.
    You can write your own code using the Shoelace formula.

    Péter Baksa
    Library Platform, Software Engineer
    GRAPHISOFT SE

  • #18591

    Harry Alex
    Blocked

    For any two basic polygons of equivalent territory, the Bolyai–Gerwien hypothesis declares that the first can be cut into polygonal pieces which can be reassembled to shape the subsequent polygon.

  • #18836

    Nader Belal
    Participant

    @Harry Alex,

    The Shoelace formula is easier to implement.

    @Jože Marinko

    Note: For calculating area of close non-self intersection polygon, the vertices must go anti-clock wise, and for negative areas (holes) you must go clock wise.

    @Harru Alex,

    Can you implement Bolyai–Gerwien hypothesis in GDL ?

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