﻿ IfcLine

#### IfcLine

Natural language names
 Linie Line Ligne
##### Semantic definitions at the entity
Entity definition

The IfcLine is an unbounded line parameterized by an IfcCartesianPoint and an IfcVector. The magnitude of the IfcVector affects the parameterization of the line, but it does not bound the line.

NOTE  A line segment is defined using either the IfcPolyline with two Points, or the IfcTrimmedCurve with BasisCurve being an IfcLine.
EXAMPLE  Figure 393 illustrates an unbounded IfcLine and a bounded line. The bounded line starting at 0.,0. and ending at 0.,2. can be defined by:
1. IfcLine with IfcVector.Magnitude: 2.0 AND IfcTrimmedCurve with Trim1: 0. and Trim2: 1. (and trimming preference being parameter);
2. IfcLine with IfcVector.Magnitude: 1.0 AND IfcTrimmedCurve with Trim1: 0. and Trim2: 2. (and trimming preference being parameter);
3. IfcLine AND IfcTrimmedCurve with Trim1::IfcCartesianPoint [0.,0.] and Trim2::IfcCartesianPoint [0.,2.] (and trimming preference being Cartesian) - the IfcVector.Magnitude has no effect;
4. IfcPolyline with Points[1] being 0.,0. and Points[2] being 0.,2.
5. IfcIndexedPolyCurve with two indices, pointing into a point list providing the coordinates (0.,0.) and (0.,2.).
 Figure 393 — Unbounded IfcLine and bounded IfcTrimmedCurve

NOTE  Definition according to ISO/CD 10303-42:1992
A line is an unbounded curve with constant tangent direction. A line is defined by a point and a direction. The positive direction of the line is in the direction of the dir vector. The curve is parameterized as follows:
P = Pnt
V = Dir
λ(u) = P + uV
and the parametric range is: -∞ < u < ∞
NOTE  Entity adapted from line defined in ISO 10303-42
HISTORY  New entity in IFC1.0
Attribute definitions
#AttributeTypeCardinalityDescription G
1PntIfcCartesianPoint The location of the IfcLine.X
2DirIfcVector The direction of the IfcLine, the magnitude and units of Dir affect the parameterization of the line.X
Formal Propositions
RuleDescription
SameDimThe dimensionality of the Pnt, provided by IfcCartesianPoint, shall be the same as the dimensionality of the Dir, provided by IfcVector.
##### Inherited definitions from supertypes
Entity inheritance
Attribute inheritance
#AttributeTypeCardinalityDescriptionG
IfcRepresentationItem
LayerAssignmentIfcPresentationLayerAssignment
@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.
IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.
IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
X
StyledByItemIfcStyledItem
@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.
IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
X
IfcGeometricRepresentationItem
IfcCurve
Dim
:=IfcCurveDim(SELF)
IfcDimensionCountThe space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. X
IfcLine
1PntIfcCartesianPoint The location of the IfcLine.X
2DirIfcVector The direction of the IfcLine, the magnitude and units of Dir affect the parameterization of the line.X
##### Formal representations
XML Specification
``` <xs:element name="IfcLine" type="ifc:IfcLine" substitutionGroup="ifc:IfcCurve" nillable="true"/>  <xs:complexType name="IfcLine">   <xs:complexContent>    <xs:extension base="ifc:IfcCurve">     <xs:sequence>      <xs:element name="Pnt" type="ifc:IfcCartesianPoint" nillable="true"/>      <xs:element name="Dir" type="ifc:IfcVector" nillable="true"/>     </xs:sequence>    </xs:extension>   </xs:complexContent>  </xs:complexType> ```
EXPRESS Specification
``` ENTITY IfcLine  SUBTYPE OF (IfcCurve);   Pnt : IfcCartesianPoint;   Dir : IfcVector;  WHERE   SameDim : Dir.Dim = Pnt.Dim;END_ENTITY;  EXPRESS-G diagram ```

References: IfcRevolvedAreaSolid IfcSurfaceOfRevolution