Represent Trimmed Curve

Overview

Identifies the information requirements for the provision of a trimmed curve.
A trimmed curve (IfcTrimmedCurve) is a bounded curve which is created by taking a selected portion, between two identified points, of an associated basis curve. The basis curve itself is unaltered and more than one trimmed curve may reference the same basis curve. Trimming points for the curve may be identified by:

parametric value
geometric position
both of the above
At least one of these is specified at each end of the curve.

Results

Specification of a trimmed curve with end points and trim conditions specified.

Description	Entity/Pset/Functional Part	MAN	REC	OPT
Select the curve that is to form the basis of the trimmed curve. A basis is a curve that is a line or conic subtype of IfcCurve. For further information, refer to the functional parts describing representation of such curves namely: fp_represent_line fp_represent_polyline fp_represent_conic (not yet defined)	IfcTrimmedCurve.BasisCurve::IfcCurve (subtypes IfcLine, IfcPolyline, IfcConic)
Specify the first trimming point for the curve	IfcTrimmedCurve.Trim1::IfcTrimmingSelect
Specify the second trimming point for the curve	IfcTrimmedCurve.Trim2::IfcTrimmingSelect
Selection of the trimming points may be either Cartesian points or parameter values or a mixture of the two. A parameter value is a REAL number defining a value within the parametric range of the curve	IfcCartesianPoint.Coordinates IfcParameterValue
The space dimensionality for a Cartesian point is derived from the number of coordinates specified.	IfcCartesianPoint.Dim
Identify whether the trimmed curve has the same sense (direction) as the basis curve. The value is set to TRUE or FALSE. Sense is used to indicate whether the direction of the trimmed curve agrees with or is opposed to the direction of the basis curve.	IfcTrimmedCurve.SenseAgreement::BOOLEAN
Where both parameter and point are present at either end of the curve, indicates the preferred form. Values may be set as: Cartesian: Indicates that trimming by Cartesian point is preferred. Parameter: Indicates the preference for the parameter value. Unspecified: Indicates that no preference is communicated.	IfcTrimmedCurve.MasterRepresentation::IfcTrimmingPreference
The space dimensionality for the trimmed curve is derived from its 2 or 3 dimensional context.	IfcTrimmedCurve.Dim

IFC Entities Required

IfcBoundedCurve
IfcCartesianPoint
IfcCurve
IfcGeometricRepresentationItem
IfcPoint
IfcRepresentationItem
IfcTrimmedCurve

IFC Datatypes Required

IfcDimensionCount
IfcLengthMeasure
IfcParameterValue
IfcTrimmingPreference
IfcTrimmingSelect

IFC Functions Required

-

IDM Functional Parts Required

-

EXPRESS-G

EXPRESS Schema

SCHEMA FP_REPRESENT_TRIMMED_CURVE;

  TYPE IfcDimensionCount = INTEGER;
    WHERE
      WR1 : { 0 < SELF <= 3 };
  END_TYPE;

  TYPE IfcLengthMeasure = REAL;
  END_TYPE;

  TYPE IfcParameterValue = REAL;
  END_TYPE;

  TYPE IfcTrimmingPreference = ENUMERATION OF
    (CARTESIAN,
     PARAMETER,
     UNSPECIFIED);
  END_TYPE;

  TYPE IfcTrimmingSelect = SELECT
    (IfcCartesianPoint,
     IfcParameterValue);
  END_TYPE;

  ENTITY IfcGeometricRepresentationItem
    ABSTRACT SUPERTYPE OF (ONEOF(IfcCurve, IfcPoint))
    SUBTYPE OF(IfcRepresentationItem);
  END_ENTITY;

  ENTITY IfcRepresentationItem
    ABSTRACT SUPERTYPE;
  END_ENTITY;

  ENTITY IfcCartesianPoint
    SUBTYPE OF(IfcPoint);
      Coordinates : LIST [1:3] OF IfcLengthMeasure;
    DERIVE
      Dim         : IfcDimensionCount := HIINDEX(Coordinates);
    WHERE
      WR1 : HIINDEX(Coordinates) >= 2;
  END_ENTITY;

  ENTITY IfcPoint
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcGeometricRepresentationItem);
  END_ENTITY;

  ENTITY IfcCurve
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcGeometricRepresentationItem);
    DERIVE
      Dim : IfcDimensionCount := IfcCurveDim(SELF);
  END_ENTITY;

  ENTITY IfcBoundedCurve
    ABSTRACT SUPERTYPE
    SUBTYPE OF(IfcCurve);
  END_ENTITY;

  ENTITY IfcTrimmedCurve
    SUBTYPE OF(IfcBoundedCurve);
      BasisCurve           : IfcCurve;
      Trim1                : SET [1:2] OF IfcTrimmingSelect;
      Trim2                : SET [1:2] OF IfcTrimmingSelect;
      SenseAgreement       : BOOLEAN;
      MasterRepresentation : IfcTrimmingPreference;
    WHERE
      WR41 : (HIINDEX(Trim1) = 1) OR (TYPEOF(Trim1[1]) <> TYPEOF(Trim1[2]));
      WR42 : (HIINDEX(Trim2) = 1) OR (TYPEOF(Trim2[1]) <> TYPEOF(Trim2[2]));
      WR43 : NOT('IFC2X2_FINAL.IFCBOUNDEDCURVE' IN TYPEOF(BasisCurve));
  END_ENTITY;

END_SCHEMA;

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