ifc4x3 IfcAdvancedBrep

1语义定义

高级B-rep是一种边界表示模型，其中所有面、边和顶点都被显式表示。它是一个具有显式拓扑和基本或自由几何体的实体。B-rep的面类型为IfcAdvancedFace。高级B-rep必须满足与流形实体B-rep相同的拓扑约束。

注：已引入高级B-rep，以支持越来越多的应用程序，这些应用程序可以基于NURBS或其他B样条曲面定义和交换B-rep模型。

 

注：根据ISO 10303-514中定义的advanced_brep_shape_presentation改编的实体。

IFC4中的新实体

 

 

非正式提议：

1. 每个面是面表面；
2. 每个面表面具有由基本表面、扫掠表面或b样条表面定义的几何结构；
3. 用于定义面的边界的边均应参考边曲线
4. 用于定义面的几何图形和面边界的每条曲线应为二次曲线、直线、多段线或b样条曲线
5. 用于定义面边界的边都应通过顶点类型的顶点进行修剪
6. 用于定义面边界的任何环都不应是定向子类型

 

 

2实体继承

 

 

 

3实体属性

#	Attribute	Type	Description
IfcRepresentationItem (2)
	LayerAssignment	SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems	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.
	StyledByItem	SET [0:1] OF IfcStyledItem FOR Item	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.
IfcSolidModel (1)
*	Dim	IfcDimensionCount	This attribute is formally derived. 3 The space dimensionality of this class, it is always 3.
Click to show 3 hidden inherited attributes Click to hide 3 inherited attributes
IfcManifoldSolidBrep (1)
1	Outer	IfcClosedShell	A closed shell defining the exterior boundary of the solid. The shell normal shall point away from the interior of the solid.

 

 

ENTITY IfcAdvancedBrep
 SUPERTYPE OF (ONEOF
    (IfcAdvancedBrepWithVoids))
 SUBTYPE OF (IfcManifoldSolidBrep);
 WHERE
    HasAdvancedFaces : SIZEOF(QUERY(Afs <* SELF\IfcManifoldSolidBrep.Outer.CfsFaces |
  (NOT ('IFC4X3.IFCADVANCEDFACE' IN TYPEOF(Afs)))
)) = 0;
END_ENTITY;

 

 

 

 

 

 

 

 

 

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