构件的表示信息(Representation)是导出属性,指向的实体是IfcProductRepresentation(超类)。IfcProductDefinitionShape是构件所有描述的容器,其中IfcshapeRepresentation定义了几何形状类型,如SweptAreaSolid、BoundingBox等。

    IFC文件的内容如下:

#6= IFCCARTESIANPOINT((0.,0.,0.));
#17= IFCDIRECTION((0.,-1.,0.));
#19= IFCDIRECTION((0.,0.,1.));
#135= IFCAXIS2PLACEMENT2D(#133,#23);
#136= IFCRECTANGLEPROFILEDEF(.AREA.,'475 x 610mm',#135,474.999999999999,610.);
#137= IFCAXIS2PLACEMENT3D(#6,#19,#17);
#138= IFCEXTRUDEDAREASOLID(#136,#137,#19,4000.);
#139= IFCSHAPEREPRESENTATION(#98,'Body','SweptSolid',(#138));
#142= IFCAXIS2PLACEMENT3D(#6,$,$);
#143= IFCREPRESENTATIONMAP(#142,#139);
#150= IFCCARTESIANTRANSFORMATIONOPERATOR3D($,$,#6,1.,$);
#151= IFCMAPPEDITEM(#143,#150);
#153= IFCSHAPEREPRESENTATION(#98,'Body','MappedRepresentation',(#151))
#155= IFCCARTESIANPOINT((-305.,-237.499999999995,0.));
#157= IFCBOUNDINGBOX(#155,610.,474.999999999999,4000.);
#158= IFCSHAPEREPRESENTATION(#99,'Box','BoundingBox',(#157));
#161= IFCPRODUCTDEFINITIONSHAPE($,$,(#153,#158));
#170= IFCCOLUMN('0Ae7iOjK982gh$h7PwMCca',#41,'M_\X2\77E95F6267F1\X0\:475 x 610mm:203111',$,'475 x 610mm',#168,#161,'203111');

    #170是柱子(IfcColumn),属性Representation指向#161(IfcProductDefinitionShape)。

   #161是几何表示(IfcProductDefinitionShape),定义了构件几何形状相关的信息。包含#153(IfcShapeRepresentation),#158(IfcShapeRepresentation)。

    #158(IfcShapeRepresentation),指向了构件的包围盒#157(IfcBoundingBox),包围盒的定义包括位置#155(IfcCartesianPoint)和包围盒在三个坐标轴上的长度。

    #153(IfcShapeRepresentation),指向了构件的几何形状。为了复用几何形状的定义,使用了映射项#151(IfcMappedItem)。

    #151(IfcMappedItem)包含了两项#143(IfcRepresentationMap)和#150(IfcCartesianTransformationOperator3D)

   #139(IfcShapeRepresentation),指向了拉伸体(SweptSolid),拉伸体的定义是#138(IfcExtrudedAreaSolid),拉伸体横截面#136(IfcRectangleProfileDef),拉伸体的位置#137(IfcAxis2Placement3D),拉伸方向是#19(IfcDirection),拉伸长度是4000。

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