IfcBSplineSurfaceForm

BACnet MVD

#### IfcBSplineSurfaceForm

Natural language names

| Bézier-Spline-Flächen (verschiedene Formen)
| BSpline Surface Form
| Forme de surface Bspline

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcBSplineSurfaceForm |  |  | ADDED |

##### Semantic definitions at the type

Type definition

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.

Enumeration definition

Constant | Description
--- | ---
PLANE_SURF | A bounded portion of a plane represented by a B-spline surface of degree 1 in each parameter.
CYLINDRICAL_SURF | A bounded portion of a cylindrical surface.
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 | A torus, or portion of a torus, represented by a B-spline surface.
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.

##### Formal representations

XML Specification
`<xs:simpleType name="IfcBSplineSurfaceForm">
<xs:restriction base="xs:string">
<xs:enumeration value="plane_surf"/>
<xs:enumeration value="cylindrical_surf"/>
<xs:enumeration value="conical_surf"/>
<xs:enumeration value="spherical_surf"/>
<xs:enumeration value="toroidal_surf"/>
<xs:enumeration value="surf_of_revolution"/>
<xs:enumeration value="ruled_surf"/>
<xs:enumeration value="generalised_cone"/>
<xs:enumeration value="quadric_surf"/>
<xs:enumeration value="surf_of_linear_extrusion"/>
<xs:enumeration value="unspecified"/>
</xs:restriction>
</xs:simpleType>
`
EXPRESS Specification
`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;

EXPRESS-G diagram

`

References: IfcBSplineSurface

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