IfcVectorDifference
注:定义符合ISO/CD 10303-42:1992
此函数将输入参数的差值返回为(Arg1-Arg2)。函数返回两个输入向量的向量差作为向量。输入参数应具有相同的维数,但可以是方向或向量。如果两个输入参数都是向量,则它们必须用相同的单位表示,如果两个输入参数都是方向,则生成无单位结果。零差向量产生零量级的向量。
注:根据ISO 10303-42中不同定义的向量_改编的函数。
IFC1.5中的新函数
EXPRESS Specification
FUNCTION IfcVectorDifference (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;
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