986 Part VI Customizing AutoCAD

Summary

In this chapter, you discovered how to create your own linetypes and hatch patterns. You read about the following:

Creating simple linetypes that contain only dashes, dots, and spaces

Making complex linetypes that include shapes and text

Constructing your own hatch patterns that are made up of a set of parallel lines In the next chapter, you read about how to create shapes and fonts.

988 Part VI Customizing AutoCAD

Figure 32-1: The Select Shape or Font File dialog box.

Using shape files

After you have a compiled a shape file, you must load it with the LOAD command before you can place it in a drawing. The Select Shape File dialog box opens. Choose the .shx file and click Open. Font files don’t have to be loaded because they’re automatically referenced by text styles that use the font files.

To insert a shape, use the SHAPE command prompts as follows:

Enter shape name or [?]: Type the name of the shape, or type ? to get a list of loaded shapes.

Specify insertion point: Pick a point on the screen. AutoCAD drags the shape as you move the cursor.

Specify height <1.0000>: This functions like a scale factor. For example, type .5 to insert the shape at one-half its original size.

Specify rotation angle <0>: Type a rotation angle.

Creating shape files

Shape files and font files are essentially the same. In this section, I explain how to create shapes. At the end of the chapter, I explain the few distinctions necessary to create a font file.

As with most customizable files, you use a text editor to create shape files. You can add comments by preceding them with a semicolon. A shape definition has the following syntax:

*shapenumber,#ofspecs,SHAPENAME spec1,spec2,...,0

The definition must start with an asterisk. Each line cannot contain more than 128 characters. Table 32-1 explains the parts of this shape definition.

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Table 32-1: The Parts of a Shape Definition

shapenumber You can use any number from 1 to 255. Each shape in a file must have a unique number.

#ofspecs This is the number of specifications in the second line of the definition, including the mandatory 0 at the end.

SHAPENAME You must use uppercase for the shape name. This is the name you use with the SHAPE command.

spec1... This is a code that defines the actual shape. Each specification code defines a part of the shape, such as a line segment or an arc. Together, all of the specifications draw the shape.

0The definition must end with a 0.

Using length and direction codes

You can use two sets of codes to define a shape. The first set, the length and direction codes, only allows you to draw straight line segments. You use this system to create specifications in the three-character hexadecimal format.

The first character is 0, which tells AutoCAD that the next two characters are hexadecimal values.

The second character is a length in units. The maximum is 15 units. The number values can range from 0 to 9. For values from 10 to 15, use A to F. Keep in mind that the length is measured along the nearest X or Y distance. Therefore, diagonal lengths are not true lengths.

The third character is a direction code. Figure 32-2 shows how this code works. Use the code that represents the desired direction of the line from the start point.

Figure 32-2: The direction codes.

Here is the code for the shape shown in Figure 32-3:

*2,4,PENNANT

044,02F,029,0

990 Part VI Customizing AutoCAD

Figure 32-3: The PENNANT shape.

Here’s how this shape works:

2 is the shape’s unique number.

4 is the number of bytes (specifications) on the second line of the definition.

PENNANT is the shape’s name.

044 draws the pole, a line that is 4 units in the vertical direction.

02F draws the top line of the pennant, a line that is approximately 2 units in the F direction. (See the following note.)

029 draws the bottom line of the pennant, a line that is approximately 2 units in the 9 direction. (See the following note.)

Using supplemental shape codes

The length and direction codes have a number of limitations:

You can draw in only 16 directions.

The maximum length of a line is 15 units.

You can draw only straight line segments.

The shape has to be continuous; you cannot lift the “pen” up and start in a new place.

The second set of codes, called the supplemental shape codes, brings additional flexibility (and complexity) to your shapes. Table 32-2 lists these codes, which can be in either hexadecimal or decimal format.

Table 32-2: Supplemental Shape Codes

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start_offset,end_offset,high_radius,radius,(-)0SC.

The start offset specifies how far past an octant the arc begins and is calculated as follows: (starting degrees – degrees of the last octant passed) * 256/45.

The end offset specifies how far past an octant the arc ends and is calculated as follows: (ending degrees – degrees of the last octant passed) * 256/45.

For both the start and the end of the arc, the last octant passed is specified in degrees, not the numbers in Figure 32-4, and is always a multiple of 45.

Continued

992 Part VI Customizing AutoCAD

Figure 32-4: The codes for octant arcs.

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The most common use for shapes is to create fonts. Here are a few examples:

*3,22,ALEF

010,07E,010,2,8,(–6,5),1,8,(–2,–4),01C,2,8,(5,2),1,8,(2,4),014,0

This is a squared-off alef, the first letter of the Hebrew alphabet, as shown in Figure 32-5. Displaying non-Roman fonts is a common use for shapes.

Figure 32-5: A squared-off alef.

Planning in advance is almost essential. A common technique is to draw the shape in a drawing on a grid set to 1-unit spacing. You can use only integers in your shape codes, so you must often scale the shape up so that the smallest line segment is 1 unit.

Here’s how the code for the alef works:

The shape starts at the top left. The code 010 is a hexadecimal length and direction code that specifies a line with a length of 1 unit and a direction of 0 degrees.

The second code, 07E, is also a hexadecimal length and direction code. It specifies a line with a length of 7 units in the E direction (315 degrees). Although the line is not actually 7 units long, its X (and in this case Y) distance is 7.

The third code, 010, is the same as the first code and ends the first set of line segments.

The fourth code, 2, lifts up the pen so that you can move to the start of the next line.

The fifth code, 8, indicates that the following two codes will be an X,Y displacement.

The sixth and seventh codes (-6,5) are placed in parentheses for readability. They move the pen (while it is up) –6 units in the X direction and +5 units in the Y direction from the end of the last line to the start of the next line. (Count the grid dots to find it.)

The eighth code, 1, puts the pen down so that you can draw.

The ninth code, 8, is the same as the fifth code.

The tenth and eleventh codes (-2,-4) draw the first segment of the second line so that the endpoint is –2 units in the X direction and –4 units in the Y direction from the start point.

994 Part VI Customizing AutoCAD

The twelfth code, 01C, is a hexadecimal code and finishes the second line with a 1-unit line segment in the C direction (270 degrees).

The thirteenth code, 2, lifts up the pen again.

The fourteenth code, 8, is the same as the fifth code.

The fifteenth and sixteenth codes (5,2) move the pen (which is up) +5 units in the X direction and +2 units in the Y direction.

The seventeenth code, 1, puts the pen down again.

The eighteenth code, 8, is the same as the fifth code.

The nineteenth and twentieth codes (2,4) draw a line whose endpoint is 2 units in the X direction and 4 units in the Y direction from its start point.

The twenty-first code, 014, is a hexadecimal length and vector code that draws a 1-unit line in the 4 (90-degree) direction.

The twenty-second code, 0, ends the shape definition.

Here’s another example, a script alef, which is shown in Figure 32-6:

*4,10,S-ALEF 06C,2,8,(6,5),1,10,(3,016),0

Figure 32-6: A script alef.

Here’s the explanation of the code for the script alef:

The first code, 06C, creates the line on the left, starting at the top and making it 6 units long.

The second code, 2, lifts up the pen.

The third code, 8, specifies an X,Y displacement, with the pen up.

The fourth and fifth codes (6,5) move the pen 6 units to the right and 5 units up, to the start of the arc.

The sixth code, 10, introduces an octant arc.

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STEPS: Creating a Shape

1.Open ab32-a.dwg from the CD-ROM.

2.Save the file as ab32-01.dwg in your AutoCAD Bible folder. This drawing shows an uppercase P, with dashed lines to indicate space before and after the letter, as shown in Figure 32-7. This is the type of drawing that you might use as a basis for creating a shape definition.

Figure 32-7: An uppercase P.

3.Type notepad on the command line and press Enter at the File to edit: prompt to open a new file.

4.Type the following in Notepad:

*80,15,UCP

2,030,1,0E4,020,12,(0,–8,–127),028,2,8,(9,–6),0

5.Press Enter at the end of the last line. Choose File Save in Notepad and save the file in your AutoCAD Bible folder as ab32-01.shp. Close Notepad.

996 Part VI Customizing AutoCAD

6.In AutoCAD, type compile . Double-click ab32-01.shp. AutoCAD compiles the .shp file. AutoCAD confirms on the command line that the compilation succeeded. (Press F2 to open the Text Window if necessary.)

7.Type load and choose ab32-01.shx. Click Open. Type shape . To insert the shape, follow the prompts:

Enter shape name or [?]: ucp

Specify insertion point: Pick any point. Specify height <1.0000>:

Specify rotation angle <0>:

8.Save your drawing. It should look like Figure 32-8.

Figure 32-8: The picture and shape of the letter P.

Editing shape files

You don’t often get a shape right the first time, and you don’t see the result until after you’ve compiled, loaded, and inserted the shape. Editing shape files involves the following steps:

1.Erase all copies of the shape.

2.Purge the .shx file by using the PURGE command and choosing Shapes in the dialog box. (You may sometimes need to purge more than once.) If you forget this step, when you try to insert the corrected shape, AutoCAD uses the old definition!

3.Edit the .shp file. Don’t forget to change the #ofspecs value in the first line if necessary. Save the file.

4.Recompile the .shp file.

5.Reload the .shx file.

6.Reinsert the shape using the SHAPE command.