In ObjectLand boundaries of area and image features are always polygons, that is, they are made up of segments of straight lines. For approximate display of a curved boundary a polygon with sufficiently large number of vertices can be used.
A circle is the most widespread type of curved boundaries. To facilitate the process of building polygons describing a circle approximately the operation of transforming a boundary to a circle can be used.
It should be emphasized that actually as a result of the transformation not a “real” circle will appear, but a polygon which displays the circle approximately.
This operation can be performed in the mode Edit, and it is required that one area or image feature was selected.
If the selected feature has inner boundaries a question arises which of its boundaries should be transformed. To determine it one should switch on the submode Editing vertices and select one of the vertices of the necessary boundary.
Then the context menu command Transform+Boundary to Circle should be performed. A dialog box “Transforming boundary to circle” shown at figure 18-14 will be opened.
Figure 18-14. Dialog box “Transforming boundary to circle”
In the fields of this dialog box automatically calculated parameter values of the polygon modeling the circle are displayed by the system. By default, a polygon with 36 vertices is used. Circle center is determined as an arithmetic average of all vertices of the original polygon, circle radius – as an arithmetic average of distances of all vertices from the calculated center.
The user can change quantity of points, center coordinates and the value of circle radius. After the button Perform is pushed the system performs transformation of the boundary.
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