AutoCAD

Add a new dimension to your AutoCAD text

1 May, 2000 By: Bill Fane


Several readers inquired about the possibilities and procedures for making 3D text in AutoCAD. Usually they are designing a casting or an injection molding, and the casting needs some lettering built into it. You can turn regular text objects into 3D objects in several different ways. Let’s start by looking at the one that is totally useless for our purposes. Figure 1 shows a bit of text that uses AutoCAD’s standard Txt font. Besides looking crude and angular, it has only two dimensions. If you give the text thickness and look at it from a suitable 3D viewing angle, it appears to have a third dimension. As figure 2 indicates, however, the text is not really 3D. It’s 2.5D in that it is composed of a series of straight-line segments with vertical thickness. In effect, these segments are very thin walls. A series of short, straight segments form curves. The lines have no width and the text is not a solid, so you can’t add or subtract it from a solid part.

 
Figure 1. Standard 2D text. Figure 2. You can assign thickness to standard text so it appears to be 3D, but it’s not really solid.

Figure 3 shows the result of changing to the Romant font. The segments of the characters now appear to have width, but in fact still comprise a series of thin, flat wall segments.

 
Figure 3. Some fonts appear to include characters whose segments have width, but they are really just multiple thin lines. Figure 4. Segments of the characters in True Type fonts have width and can be exploded and used for 3D work.

The basic problem is using the standard SHX font files supplied with AutoCAD. The good news is that AutoCAD supports standard Windows TrueType fonts. Their definition files use the extension TTF, and a directory listing shows a standard TT icon beside their names.

Each segment of a TrueType character does indeed have 2D width, as shown in figure 4. Unfortunately, the segments don’t support thickness, so you can’t make them 3D.

I wouldn’t create a problem without already knowing the solution. Just explode the text characters into a series of polylines. You can then extrude the polylines into solids.

I tried to explode text, but AutoCAD won’t let me.

It will under the right conditions. Conditions vary depending on your AutoCAD release.

Release 2000
Release 2000 provides a simple way to turn text characters into polylines. If you were smart enough to install the optional Express Tools, the Txtexp command is available. If not, dig out your AutoCAD installation CDROM and install them now.

Txtexp explodes text into a series of polyline loops that you can directly extrude into solids that you then add to or subtract from the base part.

For best results, you probably want to do some editing first. Many of the more complex characters produce multiple loops. The center of an a or e seems to need an extra loop, but AutoCAD does it differently. You’d expect p, for example, to comprise an outer profile and inner "eye" profile. Close examination reveals that p is actually built up from three separate loops, as shown in figure 5. You can always extrude each loop separately, but it’s usually worth the few extra minutes to fix things up so you can produce each character as a single solid.

All you need to do is explode the polyline loops, then erase the extra lines, as indicated in red in figure 6. Note that two coincident lines exist at each location, one from each profile.

 
Figure 5. Many characters explode into multiple segment loops. Figure 6. You can obtain better results if you explode the polylines, erase the red dividers, then use Pedit to turn things back into a single polyline loop.

Now start the Pedit command. Pick a line segment within a character. AutoCAD tells you it is not a polyline and asks if you want to turn it into one. Reply Yes. Next, enter a J to join more segments to it and select the rest of the character. This turns the profile into a single closed polyline.

Repeat this process for each character, and for each eye within those characters that have them.

Now extrude the profiles into solid characters and subtract the eyes from characters that have them. You end up with solid characters as shown in figure 7.

figure
Figure 7. Here we are! Solid 3D characters.
figure
Figure 8. You can add or subtract solid characters from an existing solid part.

You can now add or subtract the solid characters to or from your main part to produce the effect shown in figure 8. If you look very closely you realize that this is not an optical illusion—it just looks like one. The upper characters do indeed project outward, and the lower ones are cut in.

Release 14
The basic technique for Release 14 is a bit different than for AutoCAD 2000.

For starters, you don’t have to install the Express tools to get the Txtexp command. You install the Bonus tools.

The Txtexp function in Release 14 has one other difference. Instead of producing a few polyline loops as it does in AutoCAD 2000, it produces hundreds of short, straight-line segments, as shown in figure 9. Your assignment is to erase all of the diagonal connecting lines, leaving only the line segments that form the main profiles. Note that the line segments travel in pairs, so you must erase two at every location.

Figure 9. AutoCAD Release 14 produces individual lines when you explode text.

You also need to zoom in closely at the near-horizontal regions of curved sections to make sure you get the right lines. You end up with something like figure 6, but without the red lines.

As with AutoCAD 2000, you can now use Pedit to turn the line segments into polylines. Extrude the lines into solid characters, then add them to or subtract them from the existing part to produce figure 8.

Release 13
As far as I know, Release 13 has no equivalent to the Txtexp command. You can use a manual workaround, how ever. Set the TEXTFILL variable to zero, then issue the Wmfout command to create a Windows Metafile. Now use Wmfin to bring the Metafile back in, and explode it. You get the outline profile of figure 6, minus the red lines. They are already polylines, so all you have to do is extrude them.

Gnarly bits
If you use Mechanical Desktop, make sure you go to Part Preferences and turn off Apply Constraint Rules before you select the profile polylines. If you don’t, Mechanical Desktop distorts the character profiles as it attempts to clean up your "messy" sketch.

Note that Txtexp produces all its objects on layer 0 (zero), with the color of each object set separately to match the color of the layer on which the text resided, regardless of any other color or layer settings that may be in effect.

One final caution: solid models that include solid text get very large very quickly. The drawing file for figure 8 runs about 1.4MB.

And now for something completely different
Inflatable boats are made using two different materials, depending on the brand. Hence there are two different patching procedures. Zodiac and several others use a single-component glue, whereas Avon uses a mixed two-component glue. If you use the wrong one, the patch falls off after a short time. Now you’re sunk.


AutoCAD Tips!

Lynn Allen

Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's free Tips & Tools Weekly e-newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!
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