IFC 4.3.x development

8.9.2.4 IfcBSplineSurfaceForm

8.9.2.4.1 Semantic definitions at the entity

The IfcBSplineSurfaceForm represents a part of a surface of some specific form.

NOTE  Definition according to ISO/CD 10303-42:1992
This type is used to indicate that the B-spline surface represents a part of a surface of some specific form.

NOTE  Type adapted from b_spline_surface_form defined in ISO 10303-42.

HISTORY  New type in IFC4.

Items

PLANE_SURF

A bounded portion of a plane represented by a B-spline surface of degree 1 in each parameter.

CYLINDRICAL
CONICAL_SURF

A bounded portion of the surface of a right circular cone.

SPHERICAL_SURF

A bounded portion of a sphere, or a complete sphere, represented by a B-spline surface.

TOROIDAL
SURF_OF_REVOLUTION

A bounded portion of a surface of revolution.

RULED_SURF

A surface constructed from two parametric curves by joining with straight lines corresponding points with the same parameter value on each of the curves.

GENERALISED_CONE

A special case of a ruled surface in which the second curve degenerates to a single point; when represented by a B-spline surface all the control points along one edge will be coincident.

QUADRIC_SURF

A bounded portion of one of the class of surfaces of degree 2 in the variables x, y and z.

SURF_OF_LINEAR_EXTRUSION

A bounded portion of a surface of linear extrusion represented by a B-spline surface of degree 1 in one of the parameters.

UNSPECIFIED

A surface for which no particular form is specified.

8.9.2.4.1 Formal representations

TYPE IfcBSplineSurfaceForm = ENUMERATION OF
	(PLANE_SURF
	,CYLINDRICAL_SURF
	,CONICAL_SURF
	,SPHERICAL_SURF
	,TOROIDAL_SURF
	,SURF_OF_REVOLUTION
	,RULED_SURF
	,GENERALISED_CONE
	,QUADRIC_SURF
	,SURF_OF_LINEAR_EXTRUSION
	,UNSPECIFIED);
END_TYPE;