LT Unlimited

Defining Combinations of Object Snaps

In addition to a checkbox in the Drafting Settings dialog, an icon on the status bar, and a 3-letter keyboard shortcut, each Object Snap has its own unique numeric identifier.

• 0 - NONe
• 1 - ENDpoint
• 2 - MIDpoint
• 4 - CENter
• 8 - NODe
• 16 - QUAdrant
• 32 - INTersection
• 64 - INSertion
• 128 - PERpendicular
• 256 - TANgent
• 512 - NEArest
• 1024 - Clears all object snaps
• 2048 - APParent Intersection
• 4096 - EXTension
• 8192 - PARallel
• 16383 - All object snaps

When you turn on a running object snap, it gets added to the value of the OSMODE system variable. For example, if you had only Endpoints and Centers turned on, OSMODE would be 5. The way that the values are defined means that every possible combination yields a unique sum.

According to Help, the default is 4133, which corresponds to End, Center, Intersection, and Extension. Once you get your own preferred snaps, you can check the value of OSMODE and save it for future reference. You could just remember it, or you could assign different values to buttons on the ribbon to activate different combinations for different tasks.

My favorite OSMODE is 4223 -- what's yours?

Scale Objects in One Direction Only

Usually when you scale something, you want to apply the same scale factor to all your objects in all directions. For instance, two rectangles that were 4x6 and 5x7 might become 8x12 and 10x14 after scaling.

But what if you wanted the rectangles to become 4x12 and 5x14 -- so they were scaled in only one direction? Okay, you could use the stretch command, but you'd have to do it twice, since the change in the rectangles isn't the same.

Instead, you can make a temporary block consisting of the objects you want to scale, and change its properties so that it has non-uniform scales in the X and Y directions. Then, when you explode the block, you get your original objects back, but scaled in one direction only (or by different factors for each direction).

As usual, there are a couple things to keep in mind. You have to watch out for polylines with arc segments. Non-uniformly scaled arcs become elliptical arcs, and polylines don't support those. So when you explode your temporary block, any polylines with arcs will be exploded into their component lines and (elliptical) arcs.

Also, for the last few releases, you have been able to specify that blocks can only be scaled uniformly -- obviously you need to turn that off to use this tip. You can either do that when you create the block, or from the Properties palette inside the Block Editor with no objects selected.

Edit Multiple Polylines

An often-overlooked option in the Edit Polyline command is Multiple. The reason that it's overlooked is that it's the very first option to appear -- if you select an polyline right away, you won't see it again.

Select polyline or [Multiple]:

If you enter M before selecting anything, you can select multiple objects (polylines, lines, or arcs) to edit at once. The options you see next are just a little different from what you'd see selecting a single object:

Enter an option [Close/Open/Join/Width/Fit/Spline/Decurve/Ltypegen/Reverse/Undo]:

A single-object selection will show only Close or Open, not both, and also includes the Edit Vertex option.

All the options work the same whether you select one polyline or many, except for Join. That one's a little different for multiple polylines, and it's actually the main reason I use the Multiple option.

With the single-object PEDIT, the Join option only adds objects to the original polyline if their endpoints are the same. With multiple objects, though, you're given the object to set a fuzz distance and join type, in case the objects you'd like to join don't have matching endpoints.

Enter fuzz distance or [Jointype] <0.0000>:

The fuzz distance sets the maximum spacing for two object endpoints before they're joined together. A fuzz distance of 0 means that only coincident objects will be joined.

The join type determines how two endpoints within the specified fuzz distance are connected. You can choose between Extend (which lengthens the two segments until they connect), Add (which draws a new segment between the two endpoints), or Both (which extends when possible, and otherwise adds a segment).

Depending on your situation, you may find the precision of single-object joining to be better, or you might prefer to have the flexibility of the fuzz distance. Either way, it's nice to have options.

Object selected is not a polyline...Yeah, I know!

If you've ever tried to use the Edit Polyline (PEDIT) command on a line or arc, you're probably familiar with the following warning:

Object selected is not a polyline.
Do you want to turn it into one? <Y>

For me, 99% of the time, my answer is yes. If I'm selecting a non-polyline, it's because I needed to turn it into one so I could edit it in a way not supported by the original object type.

If you're the same way, you probably get tired of pressing Enter every time to turn your objects into polylines. Fortunately, there's a system variable that eliminates this question once and for all.

Just set PEDITACCEPT to 1, and that prompt will disappear forever...or at least until you set it back to 0.

If you're the type who only ever needs to use PEDIT on actual polylines, though, keeping PEDITACCEPT at 0 may make sense for you. That way, if you accidentally select a line or arc, you can just enter N to get back to the Select polyline prompt.

Move, Scale, and Rotate with ALIGN

The last two posts had videos showing you the reference options in the Scale and Reference commands. Today's will show you how to combine them (and the Move command) into one quick and easy command called ALIGN.

ALIGN is new to LT 2010.

As usual, if you can't get to YouTube, the video is available here.

Scale with Reference option

In the last post, I showed you how to use the Reference option with the Rotate command to match objects' angles without knowing anything about them.

Today, it's the Scale command's turn.

If you can't get to YouTube, you can download the video here. (2 MB)

Rotate with Reference option

Last week, I had the opportunity to talk to several customers, and I was really surprised at the number of them who didn't know about the Reference option in the Rotate and Scale commands. This is something that I use all the time, and everyone I showed it to couldn't wait to take it back to their office and show their colleagues.

So, to continue my campaign to raise awareness of the Reference option, I'm dedicating this week's series of blog posts to the topic. (Maybe I should make ribbons instead.)

It's another in my series of video posts -- actions speak louder than words, right?

If you can't see YouTube videos, you can download the MP4 file instead (2 MB).

Convert Spline to Polyline

Splines can be useful objects in a drawing, but sometimes you need to edit them with tools that apply to polylines instead. AutoCAD LT 2010 includes a function to enable you to convert a spline into a polyline so you can edit away.

You can find this function in two places: the Edit Spline command and the Edit Polyline command. It doesn't matter which one you choose; Edit Polyline just adds an extra prompt at the beginning to confirm that you want to make the conversion.

So here's the original spline:

When I start the Convert function, I'm prompted for a precision. This number can be anywhere from 0 to 99, with a higher number generating more fit points. As you'll see, low numbers tend to work pretty well.

Here's the spline after being converted with a precision of 10:

Pretty close, right? But this polyline only consists of straight-line segments. You can get an even better fit with an even lower precision value if you choose to create a poyline consisting of arc segments instead. This is controlled by the PLINECONVERTMODE variable -- 0 means straight lines and 1 means arcs.

Here's the spline again, after being converted with PLINECONVERTMODE set to 1 and a precision of 2:

You'll probably want to play around with different combinations of precisions and conversion modes to see what will work best for your own splines.

P.S. I promise there are differences between the last two images and the first! I know it's hard to spot here, but I wanted to show how well the conversion works. Try converting a spline with PLINECONVERTMODE = 0 and a precision of 0 and you'll see the "least accurate" version.

Reverse Line Direction

Another of the tiny-yet-amazingly-helpful new commands in AutoCAD LT 2010 is Reverse. Available either as a stand-alone command (on the Modify panel of the Home tab) or as an option inside the Polyline Edit and Spline Edit commands, Reverse was added to help you control the display of linetypes that contain text or symbols.

For most linetypes (Hidden, Dashdot, etc.), it doesn't matter whether they go up or down, backwards or forwards -- they'll still look the same. For linetypes that contain text or symbols, though, the direction makes a big difference in readability. If objects with these linetypes are drawn left-to-right, the text comes in right-side up. But if they're drawn right-to-left, the text shows upside down.

In this screenshot, the "Gas" line is clearly upside down -- it would be much more readable if the text were right-side up.

No problem. Just start the Reverse command, select the line, and it gets flipped so that the text is readable.

Objects that can be reversed include lines, polylines, and splines. There's no "global" option -- you have to specify which objects to reverse -- but it sure beats swapping endpoints one object at a time!

Stretch Multiple

A recent improvement (introduced sometime after version 2004) to the STRETCH command means that you no longer need to get exactly what you meant to stretch with the first crossing window. It now accepts multiple window selections, so if you either miss the first time, or have objects in different areas that can’t be selected with a single window, you don’t have to start the command over again.