8.9.6.11 IfcFirstProjAxis

8.9.6.11.1 Semantic definition

{ .extDef}

8.9.6.11.2 Formal representation

FUNCTION IfcFirstProjAxis
(ZAxis, Arg : IfcDirection) : IfcDirection;
LOCAL
XAxis : IfcDirection;
V : IfcDirection;
Z : IfcDirection;
XVec : IfcVector;
END_LOCAL;
IF (NOT EXISTS(ZAxis)) THEN
RETURN (?) ;
ELSE
Z := IfcNormalise(ZAxis);
IF NOT EXISTS(Arg) THEN
IF (Z.DirectionRatios <> [1.0,0.0,0.0]) THEN
V := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([1.0,0.0,0.0]);
ELSE
V := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,1.0,0.0]);
END_IF;
ELSE
IF (Arg.Dim <> 3) THEN
RETURN (?) ;
END_IF;
IF ((IfcCrossProduct(Arg,Z).Magnitude) = 0.0) THEN
RETURN (?);
ELSE
V := IfcNormalise(Arg);
END_IF;
END_IF;
XVec := IfcScalarTimesVector(IfcDotProduct(V, Z), Z);
XAxis := IfcVectorDifference(V, XVec).Orientation;
XAxis := IfcNormalise(XAxis);
END_IF;
RETURN(XAxis);
END_FUNCTION;

8.9.6.11.3 References

IfcBaseAxis
IfcBuildAxes