IfcVectorSum

Semantic definitions at the function

Function Definition

NOTE Definition according to ISO/CD 10303-42:1992
This function returns the sum of the input arguments as (Arg1 - Arg2). The function returns as a vector the vector difference of the two input vectors. The input arguments shall both be of the same dimensionality but may be either directions or vectors. If both input arguments are vectors they must be expressed in the same units, if both are directions a unitless result is produced. A zero sum vector produces a vector of zero magnitude. If both input arguments are directions the result is unitless.

NOTE Function adapted from vector_sum defined in ISO 10303-42.

HISTORY New function in IFC2x

Formal representations

EXPRESS Specification


FUNCTION IfcVectorSum


  (Arg1, Arg2 : IfcVectorOrDirection) 
    : IfcVector;
LOCAL
  Result : IfcVector;
  Res, Vec1, Vec2 : IfcDirection;
  Mag, Mag1, Mag2 : REAL;
  Ndim : INTEGER;
END_LOCAL;

  IF ((NOT EXISTS (Arg1)) OR (NOT EXISTS (Arg2))) OR (Arg1.Dim <> Arg2.Dim) THEN
    RETURN (?) ;
  ELSE
    BEGIN
      IF 'IFCGEOMETRYRESOURCE.IfcVector' IN TYPEOF(Arg1) THEN
        Mag1 := Arg1\IfcVector.Magnitude;
        Vec1 := Arg1\IfcVector.Orientation;
      ELSE
        Mag1 := 1.0;
        Vec1 := Arg1;
      END_IF;
      IF 'IFCGEOMETRYRESOURCE.IfcVector' IN TYPEOF(Arg2) THEN
        Mag2 := Arg2\IfcVector.Magnitude;
        Vec2 := Arg2\IfcVector.Orientation;
      ELSE
        Mag2 := 1.0;
        Vec2 := Arg2;
      END_IF;
      Vec1 := IfcNormalise (Vec1);
      Vec2 := IfcNormalise (Vec2);
      Ndim := SIZEOF(Vec1.DirectionRatios);
      Mag  := 0.0;
      Res  := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0:Ndim]);

      REPEAT i := 1 TO Ndim;
        Res.DirectionRatios[i] := Mag1*Vec1.DirectionRatios[i] + Mag2*Vec2.DirectionRatios[i];
        Mag := Mag + (Res.DirectionRatios[i]*Res.DirectionRatios[i]);
      END_REPEAT;

      IF (Mag > 0.0 ) THEN
        Result := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcVector( Res, SQRT(Mag));
      ELSE
        Result := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcVector( Vec1, 0.0);
      END_IF;
    END;
  END_IF;
  RETURN (Result);



END_FUNCTION;