AutoCAD Boundary and surface domain

The concept of 6.2.1 boundary and the creation command

The so-called boundary (boundary) is the contour of a closed area, using a boundary command to automatically analyze the contour of the region according to any point in the enclosed area, and can be preserved by means of a multi-line line (polyline) or a surface field (Region). As shown in Figure 6-2.

The command is invoked in the following way:

Menu: "Draw (Drawing)" → "Boundary ... (border) "

Command line: Boundary (or alias Bo)

After the command is invoked, the system pops up the Boundary Creation dialog box, as shown in Figure 6-3.

This dialog box is part of the boundary Hatch (bounding Pattern Fill) dialog box, see the next section for boundary padding. Several options that are available in the Boundary Creation dialog box are specified below:

(1) "Object Type": The Drop-down list box includes "Polyline" and "Region (field)" Two options that specify the form of the boundary to be saved.

(2) "Boundary set": This option specifies the scope for boundary analysis, with the default entry "current Viewport", where the AutoCAD analyzes all objects visible in the current viewport when defining boundaries.

The user can also click the button to return to the plot area and select the object you want to analyze to construct a new set of boundaries. In this case, AutoCAD discards all existing boundary sets and replaces it with a new set of boundaries.

(3) "Island detection method (Island detection)": An island (Island) refers to the internal object of a closed area. The island detection method is used to specify whether internal objects are included as boundary objects. AutoCAD provides two kinds of methods for testing

① "Flood (padding)": The island is included as a boundary object.

② "Ray casting": Draw a line from the specified point to the nearest object, and then depict the boundary in a counter-clockwise direction, thus excluding the island from the boundary object.

Using different island detection methods will produce different boundaries, as shown in Figure 6-4.

When the user completes the above settings, you can click the button to select one of the enclosed areas in the plot area, and the system will automatically parse the boundary of the area and generate a multi-line or surface field to hold the boundary. If the user chooses a range that is not closed, the system pops up the "Boundary definition error (boundary definition Errors)" dialog box shown in Figure 6-5 to prompt the user to make a selection again.

Description the "boundary" command has a command-line form of "-boundary".