#### IfcSecondProjAxis

##### Semantic definitions at the function

Function Definition

Definition from ISO/CD 10303-42:1992: This function returns the normalized vector that is simultaneously the projection of arg onto the plane normal to the vector z-axis and onto the plane normal to the vector x-axis. If arg is NULL then the projection of the vector (0.,1.,0.) onto z-axis is returned.

> NOTE Corresponding STEP function: second_proj_axis. Please refer to ISO/IS 10303-42:1994, p.103 for the final definition of the formal standard.
> HISTORY New function in IFC Release 2x

##### Formal representations

EXPRESS Specification

FUNCTION IfcSecondProjAxis
(ZAxis, XAxis, Arg: IfcDirection)
: IfcDirection;
LOCAL
YAxis : IfcVector;
V : IfcDirection;
Temp : IfcVector;
END_LOCAL;
IF NOT EXISTS(Arg) THEN
V := IfcRepresentationItem() || IfcGeometricRepresentationItem () || IfcDirection([0.0,1.0,0.0]);
ELSE
V := Arg;
END_IF;
Temp := IfcScalarTimesVector(IfcDotProduct(V, ZAxis), ZAxis);
YAxis := IfcVectorDifference(V, Temp);
Temp := IfcScalarTimesVector(IfcDotProduct(V, XAxis), XAxis);
YAxis := IfcVectorDifference(YAxis, Temp);
YAxis := IfcNormalise(YAxis);
RETURN(YAxis.Orientation);
END_FUNCTION;

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