BHATCH Command

Fills an enclosed area with an associative hatch pattern

	Draw toolbar:
	Draw menu: Hatch
	Command line: bhatch

The Boundary Hatch dialog box is displayed.

If you enter -bhatch at the Command prompt, AutoCAD LT presents options on the command line.

BHATCH computes a polyline boundary from objects that make up an enclosed area. You can then fill the boundary with an associative hatch, a hatch that updates when its boundaries are modified. Hatches are stored as single hatch objects, which can reduce the amount of disk space a drawing occupies and also can reduce regen times.

The hatch entity limit is set by the MaxHatch environment setting, which is stored in the AutoCAD LT General section of the aclt.ini file. The MaxHatch environment setting is changed through the GETENV and SETENV commands. Its default value is 10000; however, if you must create very dense hatches, you can edit the MaxHatch=10000 line, assigning any value from 100 to 10000000 (10 million). A number specified outside this range is replaced by the default value (10000).

Boundary Hatch Dialog Box

Pattern Type

Specifies a pattern type:

• Pattern. Opens the Hatch Pattern Palette dialog box, which displays the pattern images. Fourteen hatch patterns conform to International Standards Organization (ISO) standards. These patterns are at the end of the pattern list in the Hatch Pattern Palette dialog box. When you select an ISO pattern, you can specify a pen width, which determines the line weight in the pattern.
• Predefined. Specifies a pattern from those defined in the aclt.pat or acltiso.pat file.
• User-Defined. Defines a pattern of lines using the current linetype.
• Custom. Specifies a custom pattern in a .pat file other than the aclt.pat or acltiso.pat file.

Pattern Properties

Sets properties for the chosen pattern:

• ISO Pen Width. Scales an ISO-related pattern based on the selected pen width. This option is available only if a predefined ISO hatch pattern is selected.
• Pattern. Specifies a predefined pattern name. AutoCAD LT stores the pattern name in the HPNAME system variable. This option is not available if User-defined or Custom is selected under Pattern Type.
• Custom Pattern. Specifies a custom pattern name. AutoCAD LT stores the pattern name in the HPNAME system variable. This option is available only if Custom is selected under Pattern Type.
• Scale. Expands or contracts a predefined or custom hatch pattern. AutoCAD LT stores the scale in the HPSCALE system variable. This option is not available if User-defined is selected under Pattern Type.
• Angle. Specifies an angle for the hatch pattern relative to the X axis of the current UCS. AutoCAD LT stores the angle in the HPANG system variable.
• Spacing. Specifies the spacing of lines in a user-defined hatch pattern. AutoCAD LT stores the spacing in the HPSPACE system variable. This option is available only if User-defined is selected under Pattern Type.
• Double. Specifies a second set of lines to be drawn at 90 degrees to the original lines in a user-defined hatch pattern. AutoCAD LT stores this information in the HPDOUBLE system variable. This option is available only if User-defined is selected under Pattern Type.

Boundary

Defines a boundary:

• Pick Points. Determines a boundary from existing objects that form an enclosed area. If Island Detection is selected in the Advanced Options dialog box, AutoCAD LT detects objects within the outermost boundary as islands that are hatched or not hatched as specified by the hatch style. The Boundary Hatch dialog box closes, and AutoCAD LT prompts for point specification.

Select internal point: Specify a point, enter u, or press ENTER to end point specification

To undo the last selection, enter u or undo.



• Select Objects. Specifies specific objects for hatching. The Boundary Hatch dialog box closes and AutoCAD LT prompts for object selection.



When you use the Select Objects option, AutoCAD LT does not detect interior objects automatically. You must select the objects within the selected boundary to ensure that those objects are hatched according to the current hatch style.



Each time you choose Select Objects, AutoCAD LT clears the previous selection set.

• Remove Islands. Removes from the boundary objects defined as islands by the Pick Points option. You cannot remove the outer boundary.



• View Selections Displays the currently defined boundary set. This option is not available when no selection or boundary has been made.
• Advanced. Displays the Advanced Options dialog box. In large drawings, the default method of defining a boundary may be slow, because AutoCAD LT examines everything visible in the current viewport. To improve the speed of hatching, redefine the boundary set in the Advanced Options dialog box.
• Preview Hatch Displays the hatching before applying it. The dialog box closes and the selected area is hatched. After viewing the hatch, click Continue to redisplay the Boundary Hatch dialog box. This option is not available if you do not select an area.
• Inherit Properties Applies the properties of an existing hatch to the current Pattern Type and Pattern Properties options. The Boundary Hatch dialog box closes, and you are prompted to select an object.

  Select hatch object: Select a hatch block

After you select an object, the Boundary Hatch dialog box is displayed with the hatch pattern properties updated to match the hatch pattern settings you selected.

Attributes

The following two options define whether the hatch is associative or exploded.

• Associative. Controls associative hatching. If you select this option, the new hatch is associative and is updated automatically when its boundaries are modified.
• Exploded. Specifies that the hatch pattern be created from individual line segments rather than as a hatch block. AutoCAD LT stores this information by preceding the pattern name with an asterisk in the HPNAME system variable. You can also use the EXPLODE command to split hatch blocks into individual line objects.

Apply

Applies the specified hatching to the drawing. The Apply option is not available when no selection or boundary is made.

Advanced Options Dialog Box

Define Boundary Set

Defines the set of objects analyzed when AutoCAD LT defines a boundary from a specified pick point.

Specifying a boundary set can produce the boundary faster because AutoCAD LT examines fewer objects. When there's no existing boundary set, the From Existing Boundary Set option is not available.Select an option:

• Make New Boundary Set. Selects a set of objects. When you choose Make New Boundary Set, all dialog boxes close to allow object selection. AutoCAD LT includes only the hatchable objects you select when it constructs the new boundary set. If there's already a boundary set, it's discarded and replaced by the new one. If you do not select any hatchable objects, AutoCAD LT retains any current set. Until you exit BHATCH or define a new boundary set, AutoCAD LT uses only the objects you have selected to construct boundaries.
• From Everything on Screen. Creates a boundary set from everything visible on the screen. Selecting this option when there's a current boundary set discards the current set and uses everything visible in the current viewport.
• From Existing Boundary Set. Selects the current boundary set.
• Island Detection. Specifies whether objects within the outermost boundary are used as boundary objects. These internal objects are known as islands.

Boundary Style

• Style Specifies the method used to hatch objects within the outermost hatch boundary: Normal, Outer, or Ignore. If there are no internal objects selected, specifying a hatching style has no effect. Because you can define a precise set of boundaries, it's often best to use the Normal style.
• Normal. Hatches inward from the area boundary. If AutoCAD LT encounters an internal intersection, it turns off hatching until it encounters another intersection. Thus, areas separated from the outside of the hatched area by an odd number of intersections are hatched, and areas separated by an even number of intersections are not.

  

• Outer. Hatches inward from the area boundary. AutoCAD LT turns hatching off if it encounters an internal intersection and doesn't turn it back on. Because this process starts from both ends of each hatch line, only the outermost level of the structure is hatched, and the internal structure is left blank.




• Ignore. Ignores all internal objects and hatches through them.






Note: Hatching concave curves with the Outer and Ignore styles can cause hatching discrepancies.

The image tile above the Style list shows an example of the selected hatching style, a group of four nested objects: text within a triangle within a square within a circle. For these image tile examples, assume that all these objects are boundary objects.

Boundary Options

• Retain Boundaries. Specifies whether the temporary boundary objects will be added to the drawing.

BHATCH (Command Line)

If you enter -bhatch at the Command prompt, AutoCAD LT presents options on the command line.

Properties / Select / Remove islands / Advanced / <Internal point> : Specify a point or enter an option

Properties (-BHATCH)

Specifies new hatch pattern properties. For more information, see the HATCH command.

Pattern (? or name / U, style) <current> : Enter a predefined pattern name, enter u, enter ?, or press ENTER

Pattern Name (Predefined)

Specifies a predefined pattern or a custom pattern name. Enter the pattern name followed by an optional hatch style code. Precede the pattern name with an asterisk (*) to fill the area with individual lines instead of a hatch block.

Scale for pattern <current> : Specify a scale or press ENTER
Angle for pattern <current> : Specify an angle or press ENTER

U (User-Defined Pattern Name)

Specifies a user-defined pattern. Enter u, followed by an optional hatch style code. Precede the u with an asterisk (*) to fill the area with individual lines instead of a hatch block.

Angle for crosshatch lines <current> : Specify an angle for the pattern or press ENTER
Spacing between lines <current> : Specify the distance between pattern lines or press ENTER
Double hatch area? <current> : Enter y to specify a second set of lines to be drawn at 90 degrees to the original lines, or press ENTER

Select (-BHATCH)

Selects specific objects for hatching.

Select objects: Use an object selection method

Remove Islands (-BHATCH)

Removes from the boundary set objects defined as islands by the Internal Point option.

Select island to remove: Select an island

Advanced (-BHATCH)

Refines the method AutoCAD LT uses to create the hatch boundary.

Boundary set / Retain boundary / Island detection / Associativity / Style / <eXit>: Enter an option or press ENTER

Boundary Set

Defines the set of objects analyzed when AutoCAD LT defines a boundary from a specified point.

New / <Everything> : Enter an option or press ENTER

Everything

Creates a boundary set from everything visible on the screen or in the current viewport. Selecting this option when there's a current boundary set discards the current set and uses everything visible on the screen or in the current viewport.

New

Creates a boundary from a selection set you define. Selecting this option when there's a current boundary set discards the current set and uses everything visible in the current viewport.

Select objects: Use an object selection method

Retain Boundary

Specifies whether or not the derived (temporary) boundary objects will be added to the drawing after hatching is completed.

Retain derived boundaries? <current> : Enter y or n, or press ENTER

Island Detection

Specifies whether objects within the outermost boundary are used as boundary objects.

Do you want island detection? <current> : Enter y or n, or press ENTER

Specifying no island detection prompts for the ray casting method.

Specify ray: Nearest / +X / -X / +Y / -Y / Angle <current> : Enter an option or press ENTER

• Nearest. Runs a line from the point you specify to the nearest object and then traces the boundary in a counterclockwise direction.



• +X. Runs a line in the positive X direction from the point you specify to the first object encountered and then traces the boundary in a counterclockwise direction.The illustration indicates that the valid internal points for positive X direction ray casting are nearest the right-hand edges of the circle. The X indicates the area that causes a boundary definition error.
• -X. Runs a line in the negative X direction from the point you specify to the first object encountered and then traces the boundary in a counterclockwise direction.



The illustration indicates that the valid internal points for negative X direction ray casting are nearest the left-hand edges of the circle. The X indicates the area that causes a boundary definition error.

• +Y. Runs a line in the positive Y direction from the point you specify to the first object encountered and then traces the boundary in a counterclockwise direction.



The illustration indicates that the valid internal points for positive Y direction ray casting are nearest the upper edges of the circle. The X indicates the area that causes a boundary definition error.

• -Y. Runs a line in the negative Y direction from the point you specify to the first object encountered and then traces the boundary in a counterclockwise direction.



The illustration indicates that the valid internal points for negative Y direction ray casting are nearest the lower edges of the circle. The X indicates the area that causes a boundary definition error.

Angle

Runs a line at the specified angle from the point you specify to the first object encountered and then traces the boundary in a counterclockwise direction.

Ray casting angle: Specify an angle

Style

Ignore / Outer / <Normal>: Enter an option or press ENTER

Specifies the method used to hatch objects within the outermost hatch boundary. If there are no internal objects selected, specifying a hatching style has no effect. Because you can define a precise set of boundaries, it's often best to use the Normal style.

• Ignore. Ignores all internal objects and hatches through them. AutoCAD stores the Ignore style code by adding ,I to the pattern name in the HPNAME system variable.





• Outer. Hatches inward from the area boundary. AutoCAD turns hatching off if it encounters an internal intersection and doesn't turn it back on. Because this process starts from both ends of each hatch line, only the outermost level of the structure is hatched, and the internal structure is left blank. AutoCAD stores the Outer style code by adding ,O to the pattern name in the HPNAME system variable.





• Normal. Ignores all internal objects and hatches through them. AutoCAD stores the Ignore style code by adding ,I to the pattern name in the HPNAME system variable.

Associativity

Specifies that the new hatch pattern updates when its boundaries are modified. Hatching created with BHATCH is, by default, associative.

Do you want associativity? <current> : Enter y or n, or press ENTER

eXit

Returns to the initial prompt of the -BHATCH command.

Internal Point (-BHATCH)

Determines a boundary from existing objects that form an enclosed area. If Island Detection is turned on, AutoCAD LT detects objects within the outermost boundary as islands and hatches them or not, depending on the current hatch style. Hatching applied is associative.

Related Commands: HATCH fills selected objects with a nonassociative hatch pattern. HATCHEDIT modifies an existing associative hatch block. BOUNDARY creates a polyline from an enclosed area.
System Variables: HPANG sets the hatching angle. HPDOUBLE specifies whether a user-defined hatch is double hatched. HPNAME sets the hatch pattern name. HPSCALE sets the hatch pattern scale. HPSPACE sets the spacing of a user-defined hatch pattern. SNAPBASE specifies the starting point for the hatch pattern.