Autodesk AutoCAD Civil 3D Feature Representation

Special FME feature attributes are used to hold AutoCAD Civil 3D entity attributes. The reader sets these attributes on the FME feature it creates for each entity it reads.

The AutoCAD Civil 3D Reader makes use of the same standard attributes as the AutoCAD DWG/DXF Reader. Please refer to the Autodesk AutoCAD DWG/DXF Reader/Writer format documentation for additional information.

Attributes that are related to Civil 3D specific entity types are described below.

Note: All attributes specific to Civil 3D entities are prefixed by aec_ rather than the standard CAD prefix of autocad_.

Geometry Representations

In general, the geometry will be identified by the autocad_entity.

Geometry Traits

In a number of Civil3D feature types such as Alignments, the geometry of a feature can be quite complicated and make use of a number of different entities, each with its own purpose. Since FME currently restricts a feature to having only one geometric element, the Civil3D Reader constructs an aggregate out of the different geometry properties that a given feature has. At each level of geometry hierarchy, a geometry contains a geometry trait called Name which identifies it.

An example taken from an Alignment element shows the Name trait in question.

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Geometry Type: IFMEAggregate
Number of Geometries: 23
--------------------------------------
Geometry Number: 0
   Geometry Type: IFMEMultiPoint
   Name(fme-system): aec_align_begin_points'
   Number of Points: 1
   --------------------------------------
   Point Number: 0
      Geometry Type: IFMEPoint
      Coordinate Dimension: 2
      (20039.54386238,20618.287148300002)
[rest of geometry omitted]
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Geometry Traits are also used to tie properties of a geometry to that geometry rather than to the FME feature that contains the geometry. Due to aggregation of geometry on FME features read by the Civil3D Reader, the following Feature attributes may be stored either as an attribute on a Feature, or as traits on a geometry.