IfcSphericalSurface

BACnet MVD

#### IfcSphericalSurface

Natural language names

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC4 Addendum 2
IfcSphericalSurface |  |  | ADDED |

##### Semantic definitions at the entity

Entity definition

The IfcSphericalSurface is a bounded elementary surface. The inherited Position attribute defines the IfcAxisPlacement3D and provides:

- SELF\IfcElementarySurface.Position: The location and orientation of the axis system for the primitive.
- SELF\IfcElementarySurface.Position.Location: The center of the spherical surface.
- SELF\IfcElementarySurface.Position.Position[3]: The z axis points at its positve direction towards the north pole, and by its negative directions towards the south pole.

> NOTE Definition according to ISO/CD 10303-42:1992

> An IfcSphericalSurface is a type of an elementary surface, which is at a constant distance (the radius) from a central point. A spherical surface is defined by the radius and the location and orientation of the surface.

> The data is to be interpreted as follows:

> > C = Position.Location
> > x = Position.P[1]
> > y = Position.P[2]
> > z = Position.P[3] (axis of spherical surface)
> > R = Radius

> and the surface is parametrised as

> > σ(u,v) = C + R cos v ((cos u) x + (sin u) y) + R(sin v) z

> where the parametrisation range is 0 ≤ u ≤ 360 degrees and -90 ≤ v ≤ 90 degrees. u and v are angular parameters and when numerical values are specified they shall use the current units for plane angle measure.

> In the placement coordinate system defined above, the surface is represented by the equation S = 0, where

> > S(x, y, z) = x2 + y2 + z2 - R2.

> The positive direction of the normal to the surface at any point on the surface is given by

> > (Sx, Sy, Sz ).

> The unit normal is given by

> > N(u,v) = cos v((cos u)x + (sin u)y) + (sin v)z,

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

> HISTORY New entity in IFC4 Addendum 2.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
2 | Radius | IfcPositiveLengthMeasure |  | The radius of the sphere. | X | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcRepresentationItem

LayerAssignment

IfcPresentationLayerAssignment
@AssignedItems

S[0:1]

Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

> IFC2x3 CHANGE The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.

X

StyledByItem

IfcStyledItem
@Item

S[0:1]

Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.

> IFC2x3 CHANGE The inverse attribute StyledByItem has been added.

X

X

IfcGeometricRepresentationItem
IfcSurface

Dim
:=3

IfcDimensionCount

The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.

> IFC4 CHANGE Derived attribute promoted from subtypes.

X

X

IfcElementarySurface
1 | Position | IfcAxis2Placement3D |  | The position and orientation of the surface. This attribute is used in the definition of the parameterization of the surface. | X | X
IfcSphericalSurface
2 | Radius | IfcPositiveLengthMeasure |  | The radius of the sphere. | X | X

##### Formal representations

XML Specification
`<xs:element name="IfcSphericalSurface" type="ifc:IfcSphericalSurface" substitutionGroup="ifc:IfcElementarySurface" nillable="true"/>
<xs:complexType name="IfcSphericalSurface">
<xs:complexContent>
<xs:extension base="ifc:IfcElementarySurface">
<xs:attribute name="Radius" type="ifc:IfcPositiveLengthMeasure" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcSphericalSurface
SUBTYPE OF (IfcElementarySurface);
Radius : IfcPositiveLengthMeasure;
END_ENTITY;

EXPRESS-G diagram

`

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