AutoCAD

The AutoCAD 2000 Express Tools Part II (The Saga Continues)

1 Aug, 1999 By: Lynn Allen


Last month, we looked at the new Express Tools in AutoCAD 2000. As a quick recap, the Express Tools are just the beloved Bonus Tools with a new name. In addition to the disguised name, many new tools have been added to make them a delectable package indeed! Most of the tools added are samples of the tools available from the www.autodesk.com/expresstools Web site (for a fee) or free of charge to you VIP subscription holders. I've talked to many VIP members who didn't know these cool tools were on their CD. So, shake the dust off of those CDs, and take a look! Or, force your CAD manager to hand 'em over! Most of the tools described here are also available for Release 14.

The Express Tools don't load up from a typical install. So, if they're missing, you may need to grab your install CD and add them to your existing configuration. See last month's column for more details on how to proceed for proper setup. I am only covering the new or enhanced Express Tools in this series.

figure
Figure 1. The Selection tools option in the Express pulldown menu gives you many different Exclude choices.
Selection Set Tools
Last month, I stopped short of the new Selection Set Tools, so I'll pick up there, as shown in Figure 1. As a quick reminder, the Get Selection Set tool (GETSEL) is another method of quick-and-dirty filtering. I recommend trying this cool tool if you haven't already done so. The newbies in this pulldown are a group of selection set exclusions. For example, let's select all of the objects that are not in this crossing window. Simply preface the usual option with an EX to indicate you want to exclude the objects (rather then Include the objects). For example, EXC is an exclusionary Crossing window, EXF is an exclusionary Fence and so on.

To use these exclusions at the standard Select objects: prompt, preface it with an apostrophe (to use it transparently). That's kind of a drag, but I suspect there's no getting around it since it's not a part of the actual AutoCAD source code. You can also use the standard selection set methods on top of the exclusions to add or subtract from the selection set.

Command: MOVE
Select objects: 'exw
First corner ... Other corner: enclose object(s) you do not want moved
Select objects:

You can also use it directly from the command prompt to create an exclusionary selection set as long as the system variable pickfirst is set to 1. The exclusion options consist of:

EXF (Exclude Fence)
EXP (Exclude Previous)
EXW (Exclude Window)
EXC (Exclude Crossing)
EXWP (Exclude Window Polygon)
EXCP (Exclude Crossing Polygon)
Polyline Join

Let's move on to the new Modify Tools where you'll find one of my very favorite additions, Polyline Join (PLJOIN).

If you've ever tried to join two polylines or lines together with the PEDIT command only to find out you can't because they're not contiguous, you are absolutely going to love this command. Contiguous means that the endpoints meet exactly. This simple command always gets a round of applause when I show it in presentations, which just goes to show that it's not always the big ticket items that get users excited! PLJOIN will prove to be a godsend to some of you.

You can also use this command on as many different groups of polylines or lines as you want, so there's no need to enter it over and over. There are essentially two steps to PLJOIN: selecting the objects you want to join and then specifying a fuzz distance. The fuzz distance is the maximum distance two endpoints of individual polylines or lines can be separated by but still be joined. If this is still confusing to you, the Express Tools help menu has a couple of good diagrams that visually show you what a fuzz distance is.


Figure 2. A group of individual contiguous lines, such as these, cannot be joined using PEDIT; however, they can be joined using PLJOIN, as shown in Figure 3.

Figure 3. The PLJOIN command was able to join these individual lines, shown in Figure 2, to make the continuous polyline shown here.
Figure 2 shows a group of individual lines that could never be joined into one polyline using the standard AutoCAD PEDIT command. We'll use PLJOIN on it to get the results shown in Figure 3-one continuous polyline. Let's review the command in more detail:

Command: PLJOIN
Select objects: Specify
opposite corner: 12 found
Select objects: (Enter)
Join Type = Both (Fillet and Add)
Enter fuzz distance or [Jointype] <0.0000>: Specify second point:
Processing pline data... Done.

I manually drew the fuzz distance by picking two points on the screen. There is also an extra option that lets you specify a particular jointype. A jointype refers to the method used to join the endpoints of separated polylines. If I'd specified a J for jointype, I'd see the following additional prompt:

Enter join type [Fillet/Add/Both] <default>:

Fillet performs a 0-radius fillet between the two endpoints before joining the two lines. If the endpoints overlap, fillet trims off the additional ends to the intersection. Add inserts an additional segment between the two endpoints and then joins the two lines. Both first tries to use Fillet within the fuzz distance. If it's not possible, then Both uses Add mode. If the two lines are nearly parallel, a fillet might produce some goofy result. In this case, Add is a better option. If you just leave the default as is, you should live happily ever after in this command.

EXTRIM and CLIPIT
Both EXTRIM (Extended Trim) and the popular CLIPIT command (Extended Clip) now support the following additional object types as clipping boundaries: ellipses, text, mtext and attribute definitions. You'll also find that CLIPIT does a better job at handling geometry that extends outside the bounds of a selected image.

SuperHatch
Moving down to the Draw options, you'll find the new SuperHatch tool. I could dedicate an entire column just to this one. If you've ever tried to create your own hatch pattern, you've known frustration at its finest. Unfortunately it's not simply a matter of drawing a pattern and then telling AutoCAD to use it as a hatch pattern. You must explain to AutoCAD how to create the pattern using pen down, pen up and direction codes (very painful). SuperHatch to the rescue! SuperHatch permits you to use raster images, blocks, external references or Wipeouts to hatch AutoCAD objects. Let's peruse it in detail.


Figure 4. In the SuperHatch dialog box is the Curve error tolerance option that lets you control the accuracy of arc or curved clipping paths.
SuperHatch launches the dialog shown in Figure 4. You'll see the four options mentioned above along with one for selecting an existing image, block, xref or Wipeout for a hatch pattern. You'll also see an option for specifying the Curve error tolerance. I pulled in the big guns to explain this option.

According to the Express Tools Programmer, Randy Kintzley, who wrote SuperHatch, "AutoCAD does not support arc or curved clipping of images and blocks, so SuperHatch approximates curved boundaries by drawing a series of short, straight segments along the curve. The Curve error tolerance setting allows you to control the accuracy of this approximation. The curve error tolerance is the maximum amount that a straight segment can stray from the true curve. Simply put, a small error tolerance results in many short segments and smooth looking arcs. Conversely, a large error tolerance results in fewer straight segments along arcs but may cause curves along the hatch boundary to look bumpy.

"You can probably guess that the trade-offs here are quality versus performance. A low error tolerance gives higher quality but comes at a performance cost in hatching and regen time; a high error tolerance value gives faster performance but a less accurate representation of the true boundary." I turned to Randy when I came across this profound statement in the Express Tools Help file, "Curve error tolerance specifies error tolerance for curves." Well, it's all clear to me now! The Help function for the Express Tools is pretty darn good, but I'd be remiss if I didn't make fun of this one entry. However, there are some nice visual examples of Curve error tolerances later in the HELP file.

In a nutshell, the smaller the Curve error tolerance value, the closer the hatching hugs any curves you are using as a boundary and the slower you go; the larger the Curve error tolerance value, the faster you go, but the hatching won't hug curves as nicely. Got it?

Let's use an example that consists of selecting an Image. The following prompts appear after selecting an image file from the standard file dialog box.

Command: superhatch
Insertion point <0,0>:
Base image size: Width: 1.000000, Height: 0.511719, Unitless
Specify scale factor <1>: pick two points on the screen
Is the placement of this IMAGE acceptable? [Yes/No] <Yes>: enter if you like
Selecting visible objects for boundary detection...Done.
Specify an option [Advanced options] <Internal point>: pick a point
Specify an option [Advanced options] <Internal point>:
\Preparing hatch objects for display...
Done.

Use TFRAMES to toggle object frames on and off.

The prompts ask you to select the scale factor of the image on the screen by inputting a number or visually indicating it by picking two points defining a rectangle. Pick a place on the screen where you can get a good look at it (not too many objects in the way). After doing so, you'll also be asked to verify that you like the results.

This is followed by the typical BHATCH method of selecting an internal point. AutoCAD automatically finds the boundaries as you select the internal points. The


Figure 5. This image consists completely of images used in SuperHatch.
final [Enter] places the SuperHatch on the drawing (after a few processing seconds). The awesome picture shown in Figure 5 consists completely of images used in SuperHatch.

You'll also notice the TFRAMES comment in the above command sequence. TFRAMES is used to toggle image and wipeout frames on and off. If you need to select a SuperHatch object, turn on the frame to do so.

This command is filled with endless possibilities. You can now create a hatch pattern on-the-fly by drawing the hatch pattern you'd like and making a block out of it. Use the block to hatch your objects. You can also use different colors and linetypes in blocks. You don't see that with standard crosshatching! Also, there's absolutely nothing to keep you from using it on 3D surfaces. You must all promise me you'll try this cool tool and share with me some of the clever things you find you can do with it!

Some Miscellaneous Changes
Wipeout now allows you to create Wipeout objects by specifying points rather than just selecting an existing polyline (nice addition).

Revcloud (Revision Cloud) sports several new additions. It is now smart enough to store the last used arc length as a multiple of the Dimscale factor. This is very helpful when it is used with drawings with varying scale factors. In addition to


Figure 6. Using the Revcloud Options, you can select Arc Style and set Arc Chord Length.

this, two styles of Cloud Arc segments are now supported: normal and calligraphy. You can set the style for your Cloud Arc segments by selecting O for Options where you'll find the dialog box shown in Figure 6. Try the new calligraphy option. It looks really nice! You'll also find that a simple <Enter> or space bar now ends the Revcloud command.

I didn't quite make it through all of the Express Tools, so the topic will spill over into next month. At the time of this writing, it's getting close to Autodesk University (depending on which of the four you attend). I look forward to meeting many of my readers at these events-be sure to come on up and introduce yourself (I don't bite!).


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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