You must create centroids for mpolygons and closed polylines before building a topology with them.
A closed polyline is a polygon produced by the POLYGON command.
Creating Centroids SamplesCreating Centroids Namespace
Use the CreateCentroids() (twoforms) functions in the AcMapUtilities namespace to create centroids.
For centroid-creation source-code samples, see Creating Centroids Samples.
Other Information Sources
- For more information about creating centroids in AutoCAD Map 3D, choose Help > Autodesk Map Help > Contents tab (or press F1), and then navigate to Using AutoCAD Map 3D (by feature) > Topology (Spatial Analysis) > Editing Topologies > Creating Centroids for Polygons.
Creating Centroids Samples
To view code samples of centroid-creation functions, open the Samples folder in your AutoCAD Map 3D ObjectARX installation and navigate to Map Samples\CreateCentroid.