IfcLine

IfcLine是由IfcCartesianPoint和IfcVector参数化的无界线。IfcVector的大小会影响线的参数化,但不会绑定线。

注:线段是使用带两点的IfcPolyline或BasisCurve为IfcLine的IfcTrimmedCurve定义的。

下图演示了一个无界IfcLine和一个有界ifctrimedcurve。从0,0开始的有界线。在0,2结束。可定义为:

①如果与IfcVector.震级:2.0和带微调1:0的IfcTrimmedCurve。修剪2:1。参数和微调;

②如果与IfcVector.震级:1.0和带微调1:0的IfcTrimmedCurve。修剪2:2。参数和微调;

③笛卡儿切边2,和切边切边2IfcVector.震级没有效果;

④点[1]为0,0的多边形。点[2]为0,2。

 

 

——无界IfcLine与有界ifcTrimedCurve

注:定义根据ISO/CD 10303-42:1992

直线是一条切线方向不变的无界曲线。直线由点和方向定义。直线的正方向是dir向量的方向。曲线参数化如下:

P = Pnt
V = Dir
λ(u) = P + uV

参数范围为:

 -∞ < u < ∞

注:实体改编自ISO 10303-42中定义的线

IFC1.0中增加的新实体

Formal Propositions

RuleDescription
SameDim The dimensionality of the Pnt, provided by IfcCartesianPoint, shall be the same as the dimensionality of the Dir, provided by IfcVector.
 

 

 

 

#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
IfcLine
1 Pnt IfcCartesianPoint [1:1] The location of the IfcLine. X
2 Dir IfcVector [1:1] The direction of the IfcLine, the magnitude and units of Dir affect the parameterization of the line. X
EXPRESS Specification
ENTITY IfcLine
 SUBTYPE OF (IfcCurve);
  Pnt : IfcCartesianPoint;
  Dir : IfcVector;
 WHERE
  SameDim : Dir.Dim = Pnt.Dim;
END_ENTITY;

 

posted @ 2020-07-10 21:51  西北逍遥  阅读(271)  评论(0编辑  收藏  举报