#### 8.4.3.3 IfcDirection

| Direction
| Richtung

The IfcDirection provides a direction in two or three dimensional space depending on the number of DirectionRatio's provided. The IfcDirection does not imply a vector length, and the direction ratios does not have to be normalized.

> NOTE Definition according to ISO/CD 10303-42:1992
> This entity defines a general direction vector in two or three dimensional space. The actual magnitudes of the components have no effect upon the direction being defined, only the ratios X:Y:Z or X:Y are significant.

> NOTE The components of this entity are not normalized. If a unit vector is required it should be normalized before use.

> NOTE Entity adapted from direction defined in ISO 10303-42.

> HISTORY New entity in IFC1.0

XSD Specification:

<xs:element name="IfcDirection" type="ifc:IfcDirection" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
<xs:complexType name="IfcDirection">
<xs:complexContent>
<xs:extension base="ifc:IfcGeometricRepresentationItem"/>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcDirection

| SUBTYPE OF (IfcGeometricRepresentationItem);

DirectionRatios | : | LIST [2:3] OF IfcStrippedOptional;

| DERIVE

Dim | : | IfcDimensionCount := HIINDEX(DirectionRatios);

| WHERE

MagnitudeGreaterZero | : | SIZEOF(QUERY(Tmp <* DirectionRatios | Tmp <> 0.0)) > 0;

END_ENTITY;

Attribute Definitions:

DirectionRatios | : | The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3])
Dim | : | The space dimensionality of this class, defined by the number of real in the list of DirectionRatios.

Formal Propositions:

MagnitudeGreaterZero | : | The magnitude of the direction vector shall be greater than zero.

Inheritance Graph:

ENTITY IfcDirection

| ENTITY IfcRepresentationItem

| INVERSE

| ENTITY IfcGeometricRepresentationItem

| ENTITY IfcDirection

DirectionRatios | : | LIST [2:3] OF IfcStrippedOptional;

| DERIVE

Dim | : | IfcDimensionCount := HIINDEX(DirectionRatios);

END_ENTITY;

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