IfcGetBasisSurface

Semantic definitions at the function

Function Definition

NOTE Definition according to ISO/CD 10303-42:1992
This function returns the basis surface for a curve as a a set of surfaces. For a curve which is not a curve on surface an empty set is returned.

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

HISTORY New function in IFC1.5

Formal representations

EXPRESS Specification

FUNCTION IfcGetBasisSurface
(C : IfcCurveOnSurface) : SET[0:2] OF IfcSurface;

  LOCAL
    Surfs : SET[0:2] OF IfcSurface;
    N : INTEGER;
  END_LOCAL;

  Surfs := [];
  IF 'IFCGEOMETRYRESOURCE.IFCPCURVE' IN TYPEOF (C) THEN
    Surfs := [C\IfcPCurve.BasisSurface];
  ELSE
    IF 'IFCGEOMETRYRESOURCE.IFCCOMPOSITECURVEONSURFACE' IN TYPEOF (C) THEN

    (* For an IfcCompositeCurveOnSurface the BasisSurface is the intersection
       of the BasisSurface of all the segments. *)

    N := SIZEOF(C\IfcCompositeCurve.Segments);
    Surfs := IfcGetBasisSurface(C\IfcCompositeCurve.Segments[1].ParentCurve);

      IF N > 1 THEN
        REPEAT i := 2 TO N;
          Surfs := Surfs * IfcGetBasisSurface(C\IfcCompositeCurve.Segments[1].ParentCurve);
        END_REPEAT;
      END_IF;
    END_IF;
  END_IF;
  RETURN(Surfs);
END_FUNCTION;