Polygon objects have four or more vertices. The last vertex is always at the same location as the first vertex, so a polygon with four vertices is a triangle. To create a polygon object, the user does the following:

1.The user either selects Object|Create|Polygon or clicks on the Create polygon object button .

2.The user continues adding vertices as described with Polylines.

3.When the polygon is complete, a final vertex will be added at the location of the first vertex to close the polygon. The polygon may be completed by double-clicking with mouse to add the last vertex of the polygon, single-clicking at the location of the first polygon or pressing the Enter key on the keyboard. Pressing the escape or delete key while creating an object deletes the last created vertex of that object. As with points, the Object Properties dialog box is used to specify the properties of the object.

If the Shift button is held down when the mouse button is clicked and there is a vertex on another visible object within 3 pixels of the cursor, the new vertex will be at the same location as the vertex on the other object.

Typical uses for polygons are to define zones with differing media properties or boundary conditions such as lakes.