When you select a closed polyline to fill with a groundcover or site hatch, you are unable to "trim" out an island or exclude an area. You select a large polyline with interior islands and select Multiple and go to select the outer boundary, click it, and it hatches the entire polyline, including all islands.
The most common cause of this issue is that AutoCAD is unable to convert the inner polyline selection to a Region object.
In order to validate the inner boundaries, the system converts each object selected to a Region object. If this operation fails, the system just hatches the entire outer boundary.
You can test for this issue by typing REGION in the Command line and then selecting a copy of the polyline. Note whether the polyline converts to a Region, or whether this action results in an error message – typically that the polyline intersects itself.
To create a polyline that the REGION command will accept, you can either:
- redraw the polyline, or (even easier) ...
- type BOUNDARY in the Command line to redraw the polyline.
If you think the area should be able to allow for a pickpoint for the interior, try using the FLATTEN command on your linework.
If the FLATTEN command prompts you to Remove hidden lines? type N for No. (Removing hidden lines might delete many lines you're actually using. Instead, just have those hidden lines flatten and then use the OVERKILL command if needed).
Want to see which areas are causing the problem? Set the HPGAPTOL system variable to 0. (Type HPGAPTOL in the Command line and then type 0 when prompted to Enter a value.) Then try placing a hatch.