LT Unlimited

Redefine a Block Insertion

Ever put some blocks in a drawing, either from a tool palette or DesignCenter, only to discover later that the source file has been changed? Fortunately, the two tools that made inserting the block easy in the first place can also help you redefine it.

All you need to do is navigate to the source file in DesignCenter or find the block on the tool palette, and right-click on the block.

In DesignCenter, your options are insert, insert & redefine, or redefine.

On a tool palette, you just have “redefine.”

Note that any “redefine” option is only available if the block already exists in that drawing. If it doesn’t, the redefine options will be grayed out.

By the way, I found the inspiration for this tip while browsing the latest edition of Michael's Corner over at CADTutor.net -- both excellent resources for all things AutoCAD.

Set Default List of Annotation Scales

Annotation Scaling – the ability to set the size of text, dimensions, blocks, and hatches based on the drawing scale – has been around since AutoCAD LT 2008.

It’s much too big a topic to cover in a single blog post – for a good run-down see these three classes from AU. (Although if there’s demand, I may consider a blog series.)

But I did want to point out a new feature that was added to Annotation Scaling in AutoCAD LT 2011: Default Scale Lists.

Since Annotation Scaling was introduced, you’ve always been able to add and remove scales from individual drawings with the Scale List dialog.

What’s changed is the behavior of the “Reset” button in the bottom left.

Before now, it simply restored the standard list of scales included with AutoCAD LT – which probably had more scales than you actually use, especially since it includes both imperial and metric scales.

In 2011, though, you can define your own default lists of scales – metric and imperial – from the User Preferences tab in the Options dialog.

Here, you can add, edit, and remove scales until you have only the ones you need. You can even change the order in which they appear. (In this dialog, “Reset” restores the original lists that are installed with the program.)

Once you have your lists defined, the Reset button in the Edit Drawing Scales dialog restores either or both of your default scale lists.

We know that drawings with lots of annotation scales can get cluttered (there’s even a Scale List Cleanup for AutoCAD LT 2009 and 2008), so this is just one more way to help you manage your scales.

Prevent a Block from Exploding

One of the biggest advantages of using blocks for repeated content in drawings is their “togetherness” – where one piece goes, the whole thing goes. That unity can disappear in a flash, though, if the block is exploded.

Depending on the type of block, this can either be necessary (say, for a detail from your library that you need to edit) or a disaster (anything with attributes).

Since the introduction of dynamic blocks (which are especially bad to explode), you’ve been able to prevent blocks from exploding at all. Instead, you’ll get a message telling you the block “could not be exploded.”

How do you apply this (wonderful) setting? Two ways.

First, when you go to create a new block, there’s a box to un-check in the Block Definition dialog.

(I’m also a fan of checking the box above it, to force the block to scale uniformly, but that’s a topic for another day.)

Second, for an existing block, there’s a setting in the Properties palette inside the Block Editor. With no objects selected, look for the Block section, and change “Allow exploding” to “No.”

Once you have this set for all the blocks that should never be exploded, you’ll be able to breathe easier—no more risk of inadvertent block breakdowns!

Editor for Multiline Attributes

Since AutoCAD LT 2008, you've been able to include multiline attributes in blocks, giving you more flexibility in entering & displaying information.

But when you go to edit the value of your multiline attribute, some things might appear to be missing:

Not a lot of options there. And sometimes, that might be okay. You don't always *need* fancy formatting in an attribute. But if you want the full power of mtext in your multiline attribute, simply set ATTIPE (as in ATTribute In-Place Editor) to 1.

ATTIPE is set to 0 by default to help maintain maximum compatibility with previous AutoCAD LT versions. But depending on who you're sending files to, there's nothing to stop you from turning the full editor on.

Block Placeholder Attributes

Regular fields can be used in text, mtext, or attributes to display object or drawing properties, like the area of a polyline or the date and time a drawing was last plotted. For most fields, it doesn't matter where you put them. Whether they're in a text, mtext, or attribute object, they'll behave the same way.

But there's a special category of fields, called "block placeholders", that can only be used inside attributes inside the block editor. The reason for this is that they're pulling properties from the block instance itself, and these properties can change as actions and parameters are adjusted.

All blocks can make use of the following properties:

• Block Unit
• Color
• Layer
• Linetype
• Linetype Scale
• Lineweight
• Material
• Name
• Object Name
• Plot Style
• Position
• Rotation
• Scale X
• Scale Y
• Scale Z
• Unit Factor

In addition, the dynamic properties unique to that block definition will also appear in that list. For example, here are the available block placeholder fields for a fluorescent light dynamic block:

And for a steel beam section:

(For my non-structural readers, those abbreviations are for Flange Width (FW), Flange Thickness (Tf), and Web Thickness (Tw).)

Let's say I decide to use the Size variable in my new attribute.

When I close the Block Editor and save changes, I can see the size of each beam next to the beam itself. (After running Synchronize Attributes, of course.)

Display grips in blocks

Normally, when you select a block or external reference, you only get one grip, at the insertion point. (You'll also get grips for unlocked attributes, but these days I hope they're the exception rather than the rule.)

If for some reason, though, you want more grips, set GRIPBLOCK to 1. Then you'll see all available grips, just as if they were regular objects in the drawing. You can't do anything with these grips, besides the standard "move" action, and if you have a lot of blocks (or a few complicated ones) they can clutter your display pretty quickly.

But knowledge is power, right? And now you know one more way to control grip display in AutoCAD LT.

Lock Attribute Position in Blocks

First off, thank you to everyone who attended yesterday's webcast on Block Attributes. We had well over 200 attendees -- an excellent turnout! If you missed it, we'll be posting it to the AutoCAD LT Training page soon.

One of the things I talked about yesterday is what it means to lock an attribute's position in a block. The image below shows a block with 3 attributes. Two are locked, one is unlocked. Can you tell which is which?
The "View Title" and "Sheet Number" (a.k.a. 1) are locked, but the "Scale" is not.

When and attribute's position is locked, the only way to relocate the attribute is to use a dynamic parameter/action combo.

When it's unlocked, the attribute's grips are displayed when you select the block, and you can use them to reposition the attribute. You can't include unlocked attribute in a dynamic action's selection set.

Personally, I prefer to lock my attributes. It's cleaner, visually, and enables me to really control the behavior and location of the attribute.

You can set an attribute to be locked or unlocked when you create it, or you can change it later from the Properties Palette.

Breakline Dynamic Block -- Part 4

It's time to wrap up our tour through the process of creating a dynamic block breakline. In the last three, posts, I walked you through the steps for adding a variety of parameters and actions to create stretch and rotation options.

Before I post the video, I want to add a few little clean-up notes:

1. In Part 3, I initially forgot to say that you need to include the linear parameters in the rotation action's selection set. Do NOT include the stretch actions -- just the parameters. If you don't, when you rotate the block, the stretch grips get left behind. (Oops.) If you include the stretch actions in the rotation action's selection set, weird things will happen when you try to use the block. A good rule of thumb is that if something odd is happening to your block the first thing you should check is whether you've included actions in selection sets.
2. You can (and probably should) also add a Base Point parameter to your block to define its insertion point. With Base Point parameters, you don't have to worry about creating your block at any particular coordinate location. They don't have any actions; just plop one in at your desired insertion point.

Okay, here you go:

If you can't get to YouTube, you can download the video here. (MP4 format, 3 MB)

Breakline Dynamic Block -- Part 3

Today's post continues the creation process for a breakline dynamic block. Here's where we left off last time, with independent stretch actions on the left and right ends of the breakline:

The last thing I want to do is add a rotation action. Sure, you could use the regular rotate command, or grip-edit the block, but having an action to rotate the breakline seems faster to me, since you've already got the block selected to change its end points. If you don't want to rotate your breakline with an action, you certainly don't have to.

As usual, I'll start by adding the rotation parameter. I'll pick the center, the radius, and the default rotation angle. Since our breakline starts out horizontal, that default angle is 0. Non-zero default angles come in handy when your default state is not horizontal. Then, any rotation can be done incrementally, instead of having to do the math back to zero. Anyway, here's what it looks like:

For a rotation parameter, the grip location is fairly arbitrary. Just put it somewhere where it'll be obvious what it affects. And there's that exclamation point again -- I'll double click on it to create the rotate action.

After double-clicking, the first prompt is to select objects. That's because, unlike linear parameters, rotation parameters can have only one action type. So there's no need to prompt you with a choice.

I select the polyline and the two distance parameters (so that the stretch grips rotate with the line), and I'm done.

Now I have a dynamic block with 3 possible actions -- stretch the left end, stretch the right end, and rotate.

On Monday, I'll post a video showing the creation process start-to-finish.

Breakline Dynamic Block -- Part 2

In the last post, I started the process of creating a dynamic block breakline, beginning with stretching the right end of the line. Here's where we left off:

Now let's go get the other side.

I prefer to have the left and right sides of the breakline stretch independently. Sometimes, things just aren't symmetrical. So to stretch the left side, I'll just repeat the process from last time.

1. Create a linear parameter from the center of the breakline to the left end.
2. Double-click the exclamation point and choose Stretch.
3. Select the left-hand grip as the associated parameter point.
4. Draw the stretch window around the left end of the breakline.
5. Select the polyline as the object to stretch.
6. Select the parameter and use the Properties palette to set the number of grips to 1.

And here's what I get:

If you like shortcuts (and who doesn't?), there's a "Linear Stretch" item on the "Parameter Sets" tab of the Block Authoring Palette. It does steps 2, 3, and 6 for you.

Maybe in your world, though, your breaklines are always symmetrical. In that case, there's no need for a second parameter. Here are two ways you can create symmetric stretching with one parameter and two actions.

1. Use a stretch action on the Distance 1 parameter with either a distance multiplier of -1 or an angle offset of 180 degrees.

This method uses the same parameter and associated point as the first stretch action, but the stretch window is on the other end.

The other difference is in the action's properties. When the right end moves right, the left end needs to move left (and vice versa). To make this happen, you can either give the action a distance multiple of -1, or an angle offset of 180 degrees. It doesn't matter which one you use.

Now we have a block with one grip that moves both ends.

2. Adjust the Distance1 parameter to have 2 grips and a base location of "midpoint", and use the action from method 1.

Until now, we've been stretching linear parameters from what's called the "startpoint", or the first defined point of the parameter. But you can also have linear parameters that stretch symmetrically from their midpoint.

First, I'll adjust the location and properties of the Distance1 parameter.


Notice that the exclamation point is back, and that the blue "x" is still in the center of the polyline. (Before, it was attached to one end of the Distance1 parameter.)

Next, I'll create the stretch action for the left side of the breakline, making sure that the "associated point" is the left end of the parameter.

I don't have to do anything special to the action -- it automatically moves the correct way.

In this configuration, moving either grip also adjusts the other side, so that the breakline once again stays symmetric.

In the next post, I'll show you how to add the optional rotation action and parameter.