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  • IfcPolyline

    IfcPolyline是一条有界曲线,只有由笛卡尔点列表定义的直线段。如果列表中的第一个和最后一个笛卡尔点相同,则多段线为闭合曲线,否则为开放曲线。

    下图演示了有界IfcPolyline,并显示了每个线段和整个多段线的参数化长度。

    带参数长度的有界IfcPolyline

    根据注释CD-03/ISO 10342定义

    多段线是由n-1条直线段组成的有界曲线,由n个点、P1、P2。。。请注意。曲线的第i段参数化如下:

    式中i-1≤u≤i且参数范围为0<≤u≤n-1。

    注:实体改编自ISO 10303-42中的折线。

    IFC1.0中增加的新实体

    Formal Propositions

    RuleDescription
    SameDim The space dimensionality of all Points shall be the same.
     

    #AttributeTypeCardinalityDescriptionC
    IfcRepresentationItem
      LayerAssignment IfcPresentationLayerAssignment
    @AssignedItems
    S[0:1] Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items. X
      StyledByItem IfcStyledItem
    @Item
    S[0:1] Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve. X
    IfcGeometricRepresentationItem
    IfcCurve
      Dim
    :=IfcCurveDim(SELF)
    IfcDimensionCount [1:1] The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. X
    IfcBoundedCurve
    IfcPolyline
    1 Points IfcCartesianPoint L[2:?] The points defining the polyline. X
    EXPRESS Specification
    ENTITY IfcPolyline
     SUBTYPE OF (IfcBoundedCurve);
      Points : LIST [2:?] OF IfcCartesianPoint;
     WHERE
      SameDim : SIZEOF(QUERY(Temp <* Points | Temp.Dim <> Points[1].Dim)) = 0;
    END_ENTITY;
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  • 原文地址:https://www.cnblogs.com/herd/p/13253596.html
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