Definition from IAI: The IfcLShapeProfileDef defines a section profile that provides the defining parameters of an L-shaped section (equilateral L profiles are also covered by this entity) to be used by the swept area solid. Its parameters and orientation relative to the position coordinate system are according to the following illustration. The shorter leg has the same direction as the positive x-axis, the longer or equal leg the same as the positive y-axis. The centre of the position coordinate system is in the profiles centre of the gravity bounding box.

The centre of gravity, if given, is located in x direction along the negative x axis, the offset value is given by the offset parameter CentreOfGravityInX, and in y-direction along the negative y axis, the offset value is given by the offset parameter CentreOfGravityInY.

HISTORY  New entity in Release IFC2x Edition 2.

IFC2x Edition 3 CHANGE  All profile origins are now in the center of the bounding box. The attribute CentreOfGravityInY has been made OPTIONAL. Upward compatibility for file based exchange is guaranteed.

Illustration:

Position The parameterized profile defines its own position coordinate system. The underlying coordinate system is defined by the swept area solid that uses the profile definition. It is the xy plane of: IfcSweptAreaSolid.Position by using offsets of the position location, the parameterized profile can be positioned centric (using x,y offsets = 0.), or at any position relative to the profile. Explicit coordinate offsets are used to define cardinal points (e.g. upper-left bound). Parameter The parameterized profile is defined by a set of parameter attributes, see attribute definition below.

Note: The black coordinate axes show the underlying coordinate system of the swept surface or swept area solid

Position The profile is inserted into the underlying coordinate system of the swept area solid by using the Position attribute. In this example (cardinal point of gravity) the attribute values of IfcAxis2Placement2D are: Location = IfcCartesianPoint(<CentreOfGravityInX>,<CentreOfGravityInY>) RefDirection = NIL (defaults to 1.,0.) Note: if the values of CentreOfGravityInX and CentreOfGravityInY are given, they are already negative values, since the shift of the centre of gravity is into the negative X and negative Y axis. Parameter If the Width parameter is not given, it defaults to the value of Depth, therefore an equal sided L-shape profile is created, if the LegSlope parameter is not given, both legs have parallel edges.

Table: Parameters of  equal-sided and non-equal sided L-shaped section definition