Map Representation

Overview

This functional part deals with the definition of a representation map (equivalent of a symbol or block) and the placement of copies of that representation map at multiple placement locations. Each representation map has an origin (normally 0.,0.,0.) and a representation (defined as for general forms of representation), which has a representation identifier and representation type, identifying its use within different representation views
The use of representation maps is significant within an IFC based exchange of information. The representation map provides a single entity to which shape definition(s) can be assigned. Copies of the representation map are made at the locations required with rotation and transformation applied as necessary.
Forms of representation can be replaced by representation maps, if the type concept, i.e. the use of an IfcMappedItem for sharing the geometric representation(s) of the type is used.

Results

A representation for a type product is defined and associated to the type product as a representation map. Occurrences of copies of the representation map are placed as mapped items with placement and transformation.

Description	Entity/Pset/Functional Part	MAN	REC	OPT
Define the representation that is to be the representation map for the product type concerned.	IfcRepresentationMap.MappedRepresentation::IfcRepresentation
A representation map can be created using any form of representation allowed within the IFC model as a subtype of IfcRepresentation and therefore comprising a set of occurrences of IfcRepresentationItem. Refer to specific functional parts dealing with different forms of representation, for example: _* fp_represent_composite_curve_ _* fp_represent_faceted_brep_solid_model_ _* fp_represent_polyline_	IfcRepresentation.Items::IfcRepresentationItem
Set the mapping origin for the representation map. The mapping origin is a placement that defines the position about which the mapped representation is mapped	IfcRepresentationMap.MappingOrigin::IfcAxis2Placement
Specify the representation map as the source for a mapped item that will define an occurrence	IfcMappedItem.MappingSource::IfcRepresentationMap
Set the transformation of the mapped item. A Cartesian transformation operator defines a geometric transformation composed of translation, rotation, mirroring and scaling. Note that IfcCartesianTransformationOperator is an abstract supertype. Achievement of transformation is through the use of subtypes as below._	IfcMappedItem.MappingTarget::IfcCartesianTransformationOperator
For all types of Cartesian transformation operation, the following attributes may be asserted:
Set the direction used to determine U[1], the derived X axis direction	<subtype>.Axis1::IfcDirection
Set the direction used to determine U[2], the derived Y axis direction	<subtype>.Axis2::IfcDirection
Set the required translation as a cartesian point. The actual translation included in the transformation is from the geometric origin to the local origin.	<subtype>.LocalOrgin ? fp_represent_cartesian_point
Specify the scaling value for the transformation For non uniform transformations (see below), this value acts as the x scale factor.	<subtype>.Scale::REAL
Derive the scale S of the transformation. This is equal to scale if that exists, or 1.0 otherwise.	<subtype>. Scl::REAL
Derive the space dimensionality of the mapped item. _This is determined by the space dimensionality of the local origin	<subtype>.Dim::IfcDimensionCount
For a 2D transformation with uniform scaling	Use <subtype> = IfcCartesianTransformationOperator2D
Derive the list of mutually orthogonal, normalised vectors defining the transformation matrix T. They are derived from the explicit attributes Axis1 and Axis2 in that order using the function IfcBaseAxis	IfcCartesianTransformationOperator2D.U::IfcDirection
For a 2D transformation with non uniform scaling Attributes as below are in addition to those defined for IfcCartesianTransformationOperator2D	Use <subtype> = IfcCartesianTransformationOperator2DnonUniform
Specify the scaling value specified for the transformation along the axis 2. This is normally the y scale factor.	IfcCartesianTransformationOperator2DnonUniform.Scale2 ::REAL
Derive the scale S(2) of the transformation along the axis 2 (normally the y axis). This is equal to Scale2 if that exists, or equal to the derived Scl1 (normally the x axis scale factor) otherwise.	IfcCartesianTransformationOperator2DnonUniform.Scl2::REAL
For a 3D transformation with uniform scaling	Use <subtype> = IfcCartesianTransformationOperator3D
Set the exact direction of U[3], the derived Z axis direction	IfcCartesianTransformationOperator3D.Axis3::IfcDirection
Derive the list of mutually orthogonal, normalised vectors defining the transformation matrix T. They are derived from the explicit attributes Axis3, Axis1 and Axis2 in that order using the function IfcBaseAxis	IfcCartesianTransformationOperator3D.U ? IfcDirection
For a 3D transformation with non uniform scaling Attributes as below are in addition to those defined for IfcCartesianTransformationOperator3D	Use <subtype> = IfcCartesianTransformationOperator3DnonUniform
Set the scaling value specified for the transformation along the axis 2. This is normally the y scale factor	IfcCartesianTransformationOperator3DnonUniform.Scale2 ::REAL
Set the scaling value specified for the transformation along the axis 3. This is normally the z scale factor	IfcCartesianTransformationOperator3DnonUniform.Scale3 ::REAL
Derive the scale S(2) of the transformation along the axis 2 (normally the y axis). This is equal to Scale2 if that exists, or equal to the derived Scl1 (normally the x axis scale factor) otherwise	IfcCartesianTransformationOperator3DnonUniform.Scl2::REAL
Derive the scale S(3) of the transformation along the axis 3 (normally the z axis). This is equal to Scale3 if that exists, or equal to the derived Scl1 (normally the x axis scale factor) otherwise	IfcCartesianTransformationOperator3DnonUniform.Scl3::REAL

IFC Entities Required

IfcAxis2Placement2d
IfcAxis2Placement3d
IfcCartesianTransformationOperator
IfcCartesianTransformationOperator2D
IfcCartesianTransformationOperator2DnonUniform
IfcCartesianTransformationOperator3D
IfcCartesianTransformationOperator3DnonUniform
IfcDirection
IfcGeometricRepresentationItem
IfcMappedItem
IfcRepresentation
IfcRepresentationItem
IfcRepresentationMap
IfcShapeRepresentation

IFC Datatypes Required

IfcAxis2Placement
IfcDimensionCount
IfcLabel

IFC Functions Required

IfcBaseAxis

IFC Property Sets Required

-

IDM Functional Parts Required

fp_represent_cartesian_point
fp_set_geometric_representation_context

EXPRESS-G

EXPRESS Schema

SCHEMA FP_MAP_REPRESENTATION;

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

  TYPE IfcLabel = STRING;
  END_TYPE;

  TYPE IfcAxis2Placement = SELECT
    (IfcAxis2Placement2d,
     IfcAxis2Placement3d);
  END_TYPE;

  ENTITY IfcAxis2Placement2d;
      RefDirection : OPTIONAL IfcDirection;
    DERIVE
      p            : LIST [2:2] OF IfcDirection := IfcBuild2Axes(RefDirection);
    WHERE
      WR1 : (NOT (EXISTS (RefDirection))) OR (RefDirection.Dim = 2);
      WR2 : SELF\IfcPlacement.Location.Dim = 2;
  END_ENTITY;

  ENTITY IfcGeometricRepresentationItem
    ABSTRACT SUPERTYPE OF (ONEOF(IfcCartesianTransformationOperator, IfcDirection))
    SUBTYPE OF(IfcRepresentationItem);
  END_ENTITY;

  ENTITY IfcRepresentationItem
    ABSTRACT SUPERTYPE OF (ONEOF(IfcGeometricRepresentationItem, IfcMappedItem));
  END_ENTITY;

  ENTITY IfcMappedItem
    SUBTYPE OF(IfcRepresentationItem);
      MappingSource : IfcRepresentationMap;
      MappingTarget : IfcCartesianTransformationOperator;
  END_ENTITY;

  ENTITY IfcRepresentationMap;
      MappingOrigin        : IfcAxis2Placement;
      MappedRepresentation : IfcRepresentation;
    INVERSE
      MapUsage             : SET OF IfcMappedItem FOR MappingSource;
  END_ENTITY;

  ENTITY IfcRepresentation;
      ContextOfItems           : fp_set_geometric_representation_context;
      RepresentationIdentifier : OPTIONAL IfcLabel;
      RepresentationType       : OPTIONAL IfcLabel;
      Items                    : SET [1:?] OF IfcRepresentationItem;
  END_ENTITY;

  ENTITY IfcShapeRepresentation
    SUBTYPE OF(IfcRepresentation);
    WHERE
      WR21 : 'IFC2X2_FINAL.IFCGEOMETRICREPRESENTATIONCONTEXT' 
             IN TYPEOF(SELF\IfcRepresentation.ContextOfItems);
      WR22 : SIZEOF(QUERY(temp <* Items | 
             ('IFC2X2_FINAL.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp))
             AND (NOT(SIZEOF(
             ['IFC2X2_FINAL.IFCVERTEXPOINT',
             'IFC2X2_FINAL.IFCEDGECURVE',
             'IFC2X2_FINAL.IFCFACESURFACE'] * TYPEOF(temp)) = 1))
             )) = 0;
      WR23 : EXISTS(SELF\IfcRepresentation.RepresentationType);
      WR24 : IfcShapeRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);
  END_ENTITY;

  ENTITY IfcCartesianTransformationOperator
    ABSTRACT SUPERTYPE OF (ONEOF(IfcCartesianTransformationOperator2D, IfcCartesianTransformationOperator3D))
    SUBTYPE OF(IfcGeometricRepresentationItem);
      Axis1       : OPTIONAL IfcDirection;
      Axis2       : OPTIONAL IfcDirection;
      LocalOrigin : fp_represent_cartesian_point;
      Scale       : OPTIONAL REAL;
    DERIVE
      Scl         : REAL := NVL(Scale, 1.0);
      Dim         : IfcDimensionCount := LocalOrigin.Dim;
    WHERE
      WR1 : Scl > 0.0;
  END_ENTITY;

  ENTITY IfcCartesianTransformationOperator2D
    SUBTYPE OF(IfcCartesianTransformationOperator);
    DERIVE
      U : LIST [2:2] OF IfcDirection := IfcBaseAxis(2,SELF\IfcCartesianTransformationOperator.Axis1,
          SELF\IfcCartesianTransformationOperator.Axis2,?);
    WHERE
      WR1 : SELF\IfcCartesianTransformationOperator.Dim = 2;
      WR2 : NOT(EXISTS(SELF\IfcCartesianTransformationOperator.Axis1)) OR 
            (SELF\IfcCartesianTransformationOperator.Axis1.Dim = 2);
      WR3 : NOT(EXISTS(SELF\IfcCartesianTransformationOperator.Axis2)) OR 
            (SELF\IfcCartesianTransformationOperator.Axis2.Dim = 2);
  END_ENTITY;

  ENTITY IfcCartesianTransformationOperator2DnonUniform
    SUBTYPE OF(IfcCartesianTransformationOperator2D);
      Scale2 : OPTIONAL REAL;
    DERIVE
      Scl2   : REAL := NVL(Scale2, SELF\IfcCartesianTransformationOperator.Scl);
    WHERE
      WR1 : Scl2 > 0.0;
  END_ENTITY;

  ENTITY IfcDirection
    SUBTYPE OF(IfcGeometricRepresentationItem);
      DirectionRatios : LIST [2:3] OF REAL;
    DERIVE
      Dim             : IfcDimensionCount := HIINDEX(DirectionRatios);
  END_ENTITY;

  ENTITY IfcCartesianTransformationOperator3D
    SUBTYPE OF(IfcCartesianTransformationOperator);
      Axis3 : OPTIONAL IfcDirection;
    DERIVE
      U     : LIST [3:3] OF IfcDirection := IfcBaseAxis(3,SELF\IfcCartesianTransformationOperator.Axis1,
              SELF\IfcCartesianTransformationOperator.Axis2,Axis3);
    WHERE
      WR1 : SELF\IfcCartesianTransformationOperator.Dim = 3;
      WR2 : NOT(EXISTS(SELF\IfcCartesianTransformationOperator.Axis1)) OR 
            (SELF\IfcCartesianTransformationOperator.Axis1.Dim = 3);
      WR3 : NOT(EXISTS(SELF\IfcCartesianTransformationOperator.Axis2)) OR 
            (SELF\IfcCartesianTransformationOperator.Axis2.Dim = 3);
      WR4 : NOT(EXISTS(Axis3)) OR (Axis3.Dim = 3);
  END_ENTITY;

  ENTITY IfcCartesianTransformationOperator3DnonUniform
    SUBTYPE OF(IfcCartesianTransformationOperator3D);
      Scale2 : OPTIONAL REAL;
      Scale3 : OPTIONAL REAL;
    DERIVE
      Scl2   : REAL := NVL(Scale2, SELF\IfcCartesianTransformationOperator.Scl);
      Scl3   : REAL := NVL(Scale3, SELF\IfcCartesianTransformationOperator.Scl);
    WHERE
      WR1 : Scl2 > 0.0;
      WR2 : Scl3 > 0.0;
  END_ENTITY;

  ENTITY IfcAxis2Placement3d;
      Axis         : OPTIONAL IfcDirection;
      RefDirection : OPTIONAL IfcDirection;
    DERIVE
      p            : LIST [3:3] OF IfcDirection := IfcBuildAxes(Axis, RefDirection);
    WHERE
      WR1 : SELF\IfcPlacement.Location.Dim = 3;
      WR2 : (NOT (EXISTS (Axis))) OR (Axis.Dim = 3);
      WR3 : (NOT (EXISTS (RefDirection))) OR (RefDirection.Dim = 3);
      WR4 : (NOT (EXISTS (Axis))) OR (NOT (EXISTS (RefDirection))) OR (IfcCrossProduct(Axis,RefDirection).Magnitude > 0.0);
      WR5 : NOT ((EXISTS (Axis)) XOR (EXISTS (RefDirection)));
  END_ENTITY;

  ENTITY fp_represent_cartesian_point;
  END_ENTITY;

  ENTITY fp_set_geometric_representation_context;
    INVERSE
      RepresentationsInContext : SET OF IfcRepresentation FOR ContextOfItems;
  END_ENTITY;

  FUNCTION IfcBaseAxis
  (Dim : INTEGER; 
       Axis1, Axis2, Axis3 : IfcDirection)
  	: LIST [2:3] OF IfcDirection;
    
    LOCAL
      U : LIST [2:3] OF IfcDirection;
      Factor : REAL;
      D1, D2 : IfcDirection;
    END_LOCAL;
    
      IF (Dim = 3) THEN 
        D1 := NVL(IfcNormalise(Axis3), IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,0.0,1.0]));
        D2 := IfcFirstProjAxis(D1, Axis1);
        U  := [D2, IfcSecondProjAxis(D1, D2, Axis2), D1];
      ELSE
        IF EXISTS(Axis1) THEN
          D1 := IfcNormalise(Axis1);
          U  := [D1, IfcOrthogonalComplement(D1)];
          IF EXISTS(Axis2) THEN
            Factor := IfcDotProduct(Axis2, U[2]);
            IF (Factor < 0.0) THEN
              U[2].DirectionRatios[1] := -U[2].DirectionRatios[1];
              U[2].DirectionRatios[2] := -U[2].DirectionRatios[2];
            END_IF;
          END_IF;
        ELSE
          IF EXISTS(Axis2) THEN
            D1 := IfcNormalise(Axis2);
            U  := [IfcOrthogonalComplement(D1), D1];
            U[1].DirectionRatios[1] := -U[1].DirectionRatios[1];
            U[1].DirectionRatios[2] := -U[1].DirectionRatios[2];
            ELSE
              U := [IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([1.0, 0.0]), 
                    IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0, 1.0])];
          END_IF;
        END_IF;
      END_IF;
      RETURN(U);
  END_FUNCTION;

END_SCHEMA;

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