A standard library of hatch patterns is provided with the product that can be used as they are or modified to suit your needs. You can also create your own custom hatch patterns.
The standard hatch patterns that come with the product are stored in two different library files, the names of those files is dependent on which product or products have been installed:
- AutoCAD and AutoCAD-based products - acad.pat and acadiso.pat
- AutoCAD LT product - acadlt.pat and acadltiso.pat
Hatch Pattern Definitions
Hatch patterns are defined in one or more definition files that have a .pat file extension. You can use the hatch patterns as they are, modify them, or create your own custom hatch patterns.
Regardless of where a definition is stored, hatch patterns have the same structure. They have a header line with a name, which begins with an asterisk and is no more than 31 characters long, and an optional description.
*pattern-name, description
A pattern definition also has one or more descriptor lines in the following format:
angle, x-origin,y-origin, delta-x,delta-y,dash-1,dash-2, …
For example, the standard hatch pattern ANSI31 looks like:
and is defined as follows:
*ANSI31, ANSI Iron, Brick, Stone masonry 45, 0,0, 0,.125
The pattern name on the first line, *ANSI31, is followed by the description ANSI Iron, Brick, Stone masonry. This simple pattern definition specifies a line drawn at an angle of 45 degrees, the first line of the family of hatch lines is to pass through the drawing origin (0,0), and that the spacing between hatch lines of the family is to be 0.125 drawing units.
Hatch pattern definitions follow these rules:
- Each line in a pattern definition can contain up to 80 characters. You can include letters, numbers, and the special characters underline (_), hyphen (-), and dollar sign ($). However, you must begin a pattern definition with a letter or number, not a special character.
- Blank lines and text to the right of a semicolon are ignored.
- Each pattern line is considered to be the first member of a line family, created by applying the delta offsets in both directions to generate an infinite family of parallel lines.
- The delta-x value indicates the displacement between members of the family in the direction of the line. It is used only for dashed lines.
- The delta-y value indicates the spacing between members of the family; that is, it is measured perpendicular to the lines.
- A line is considered to be of infinite length. A dash pattern is superimposed on the line.
The process of hatching consists of expanding each line in the pattern definition to its infinite family of parallel lines. All selected objects are checked for intersections with any of these lines; any intersections cause the hatch lines to be turned on and off as governed by the hatching style. Each family of hatch lines is generated parallel to an initial line with an absolute origin to guarantee proper alignment.
Display of Dense Hatch Patterns
If you create a very dense hatch pattern, the program may reject the hatch and display a message indicating that the hatch scale is too small or its dash length too short. Change the maximum number of hatch lines by setting the HPMAXLINES system variable to a whole number between 0 and 10000000 (ten million), in AutoCAD 2008-based products and later.
- In AutoCAD LT, use SETENV and enter a valid number.
- In non-LT products, use the AutoLISP expression (setenv "MaxHatch" "n") where n is a valid number.