IfcRectangularTrimmedSurface

Item	Change	Description
IFC4 Addendum 1
IfcRectangularTrimmedSurface
Usense	MODIFIED	Type changed from BOOLEAN to IfcBoolean.
Vsense	MODIFIED	Type changed from BOOLEAN to IfcBoolean.

Semantic definitions at the entity

Entity definition

The IfcRectangularTrimmedSurface is a surface created by bounding its BasisSurface along two pairs of parallel curves defined within the parametric space of the referenced surface.

NOTE Definition according to ISO/CD 10303-42:1992
The trimmed surface is a simple bounded surface in which the boundaries are the constant parametric lines u₁ = u1, u₂ = u2, v₁ = v1 and v₂ = v2. All these values shall be within the parametric range of the referenced surface. Cyclic properties of the parameter range are assumed. The rectangular trimmed surface inherits its parameterization directly from the basis surface and has parameter ranges from 0 to |u₂ - u₁| and 0 to|v₂-v₁|.

NOTE If the surface is closed in a given parametric direction, the values of u₂ or v₂ may require to be increased by the cyclic range.

EXAMPLE 370 degrees is equivalent to 10 degrees, for those surfaces whose parametric form is defined using circular functions (sine and cosine).

NOTE Entity adapted from rectangular_trimmed_surface in ISO 10303-42.

HISTORY New entity in IFC2x.

Informal Propositions:

The domain of the trimmed surface shall be within the domain of the surface being trimmed.

Attribute definitions

#	Attribute	Type	Description	G
1	BasisSurface	IfcSurface	Surface being trimmed.	X
2	U1	IfcParameterValue	First u parametric value.	X
3	V1	IfcParameterValue	First v parametric value.	X
4	U2	IfcParameterValue	Second u parametric value.	X
5	V2	IfcParameterValue	Second v parametric value.	X
6	Usense	IfcBoolean	Flag to indicate whether the direction of the first parameter of the trimmed surface agrees with or opposes the sense of u in the basis surface.	X
7	Vsense	IfcBoolean	Flag to indicate whether the direction of the second parameter of the trimmed surface agrees with or opposes the sense of v in the basis surface.	X

Formal Propositions

Rule	Description
U1AndU2Different	U1 and U2 shall have different values.
V1AndV2Different	V1 and V2 shall have different values.
UsenseCompatible	With exception of those surfaces closed in the U parameter, direction Usense shall be compatible with the ordered parameter values for U.
VsenseCompatible	Vsense shall be compatible with the ordered parameter values for V.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
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
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
IfcBoundedSurface
IfcRectangularTrimmedSurface
1	BasisSurface	IfcSurface		Surface being trimmed.	X
2	U1	IfcParameterValue		First u parametric value.	X
3	V1	IfcParameterValue		First v parametric value.	X
4	U2	IfcParameterValue		Second u parametric value.	X
5	V2	IfcParameterValue		Second v parametric value.	X
6	Usense	IfcBoolean		Flag to indicate whether the direction of the first parameter of the trimmed surface agrees with or opposes the sense of u in the basis surface.	X
7	Vsense	IfcBoolean		Flag to indicate whether the direction of the second parameter of the trimmed surface agrees with or opposes the sense of v in the basis surface.	X

Formal representations

XML Specification

 <xs:element name="IfcRectangularTrimmedSurface" type="ifc:IfcRectangularTrimmedSurface" substitutionGroup="ifc:IfcBoundedSurface" nillable="true"/>

 <xs:complexType name="IfcRectangularTrimmedSurface">

  <xs:complexContent>

   <xs:extension base="ifc:IfcBoundedSurface">

    <xs:sequence>

     <xs:element name="BasisSurface" type="ifc:IfcSurface" nillable="true"/>

    </xs:sequence>

    <xs:attribute name="U1" type="ifc:IfcParameterValue" use="optional"/>

    <xs:attribute name="V1" type="ifc:IfcParameterValue" use="optional"/>

    <xs:attribute name="U2" type="ifc:IfcParameterValue" use="optional"/>

    <xs:attribute name="V2" type="ifc:IfcParameterValue" use="optional"/>

    <xs:attribute name="Usense" type="ifc:IfcBoolean" use="optional"/>

    <xs:attribute name="Vsense" type="ifc:IfcBoolean" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRectangularTrimmedSurface

 SUBTYPE OF (IfcBoundedSurface);

  BasisSurface : IfcSurface;

  U1 : IfcParameterValue;

  V1 : IfcParameterValue;

  U2 : IfcParameterValue;

  V2 : IfcParameterValue;

  Usense : IfcBoolean;

  Vsense : IfcBoolean;

 WHERE

  U1AndU2Different : U1 <> U2;
  V1AndV2Different : V1 <> V2;
  UsenseCompatible : (('IFCGEOMETRYRESOURCE.IfcElementarySurface' IN TYPEOF(BasisSurface)) AND

         (NOT ('IFCGEOMETRYRESOURCE.IfcPlane' IN TYPEOF(BasisSurface)))) OR

         ('IFCGEOMETRYRESOURCE.IfcSurfaceOfRevolution' IN TYPEOF(BasisSurface)) OR

         (Usense = (U2 > U1));
  VsenseCompatible : Vsense = (V2 > V1);
END_ENTITY;

 EXPRESS-G diagram

	Rechteckig begrenzte Oberfl盲che
	Rectangular Trimmed Surface