DIMASSOC: Keep Dimensions Dynamic

Dimensions can be both the most convenient or most bothersome aspect of CAD annotations.  Today, lets look at an AutoCAD variable setting that should help DIMinish your anxieties.

Guilty by Association?

First, it is worth noting that dimensions in AutoCAD can be placed as intelligent, dynamic objects that react to changes in your drawing, or can be nothing more than an arrangement of lines and text that gives the appearance of a 'normal' dimension.

The AutoCAD variable that controls the behaviour of dimensions is DIMASSOC.  The value of DIMASSOC at the moment a dimension is created sets the property for the dimension.

DIMASSOC can have a value of either 0, 1, or 2.

DIMASSOC is a drawing variable, which means it's value is set separately in each drawing; it is not stored in any dimension style.

A setting of DIMASSOC of 0 means that created dimensions are exploded to lines, solids and text.  This is rarely a desired output, since it is not dynamic.  DIMASSOC of 1 means that created dims behave as one object, and will update as the positions of the dimension are adjusted, but does not update if the OBJECT it is dimensioning is modified.  DIMASSOC of 2 creates dimensions as single objects that will automatically follow modifications to the object it is dimensioned. 

Let's observe the difference in the following example:

The figure below shows two linear dimensions, each appearing the same as the other.  The dimension above the line has DIMASSOC=1, and the dimension below has DIMASSOC=2.

Both dimensions will update if the dimension grips are picked and the dim is grip edited. 

In the next figure, the bold line has been stretched 25 units to the right.  Note the upper dimension, with DIMASSOC=1 has not changed, but the bottom dimension with DIMASSOC=2 has automatically followed the object.

Setting DIMASSOC 2 makes your drawings and dimensions 'smarter!"

DIM EXTRA:

If you happen to have a dimension that is not associated to the object it describes, you can associate it with the AutoCAD command DIMREASSOCIATE.  This neat command will prompt for dim objects to re-associate, then prompt for the locations on the objects.  AutoCAD will then re-associate the dimensions.  FANTASTIC!

What's your DIMASSOC set at? Share your thoughts and  experiences.

AutoCAD Text Tips

Let's take a quick look at a few handy tips and tricks with AutoCAD text: Edit multiple MTEXT strings, TJUST command, and AUTOCAPS.

Edit multiple MTEXT strings

You can select multiple MTEXT strings, either by selecting them, or by Windowing them.  The Properties Palette will list the text Contents as *VARIES*.  Click on it, and an ellipsis (3 small dots) will appear.  Click that, and AutoCAD will cycle through the selected MTEXT boxes for editing.  

Click anywhere outside the editing area for AutoCAD to move to the next MTEXT string.

Justify DTEXT (TJUST)

AutoCAD has several options for changing the justification of DTEXT and MTEXT.

Users can select the text object(s) and in the properties palette select a different justification.  AutoCAD will change the justification, but it will change it based on the text insertion point.  This means that left justified text changed to right justified text will MOVE (the insert point stays the same).

DTEXT left justified.

 

DTEXT changed to right justification using the Properties Palette.

If you want to change the justification without repositioning the text, use the Express Tool TJUST. TJUST will modify the justification without changing the position of the text!  Works great when you open an old drawing and all the notes are single line text with center justification! 

 DTEXT left justified.

 

 

DTEXT changed to right justification using TJUST.

Always have uppercase MTEXT

You can always have uppercase text in your MTEXT box, even without the Caps Lock button set. Simply right-click in the text edit window to get the context menu. Left click AutoCAPS, a checkbox will appear beside it.  Now all your text will be uppercase. To create lowercase text while AutoCAPS is on, simply hold the shift button while typing.

There you go, I hope these tips help improve your AutoCAD experience!

A look at XREFs

 XREF is a great way to quickly and easily connect information from drawing to drawing.  Many users find it daunting, cumbersome, or just simply confusing.  Let's take a closer look.

An XREF (eXternal REFerence) is an external CAD file, image, or PDF that is linked to your current drawing.  AutoCAD loads the file into the current drawing and displays it, and even notifies you if a referenced file has been modified, and prompts you to reload the reference.  You can think of XREFs as blocks from another drawing. 

 

XREFs have several benefits:

• Multiple drawings can reference the same file, so updating is easy, and more than one user can access the same data.
• Layer settings for XREF drawings can be easily manipulated.
• Since all that is tracked is the insertion, rotation and scale factor, XREFs do not add much to the size of a file.
• An XREF is like a block, if you freeze the layer it is inserted on, the entire XREF is frozen.
• When the reference file is modified, all the drawings that have it are updated.
• 5 types can be XREFed: DWG, DXF, DGN (yes, Microstation files!), PDF (yes, PDF files too!), and image files (JPG, GIF, TIF, PNG, .

Types of XREFs

There are 2 types of XREF: Attachment and Overlay, which you specify in the XREF attach dialog.

Attachment means the file AND all of its XREFs get attached to when XREFed into another drawing.

Overlay means only the selected file gets referenced when XREFed to another drawing; AutoCAD ignores the XREFs that the file may have (no nested references).

To change from one to the other, toggle it in the Details area of the XREF Palette. 

Example: You have a drawing of a site, with a pipeline XREF as Overlay. If the site drawing gets XREFed into another drawing, the pipeline will not display, since overlays do not nest.

Visretain controls the appearance of XREF layers in your  drawing.  If set to 1, any changes to XREF layer properties, visibility, colour, etc is saved in the host file. When visretain is set to 0, all layer settings get reset from the XREF each time the file is loaded or reloaded.

Path and Status

An XREF can have one of several status: loaded, unloaded, orphaned, not found, unreferenced.

Loaded:            The reference is loaded into the current drawing

Unloaded:         The reference is not loaded, but AutoCAD still has the info, and can easily reload it.

Orphaned:         The reference is nested in another reference that has been unloaded. Orphaned references do not display.

Not Found:         AutoCAD cannot locate the reference file.

Unreferenced:   The XREF has been erased from the drawing file, but not detached as an XREF. AutoCAD knows where to find the XREF, but not where it is inserted.

 

The XREF path can be set as either relative, full, or none.  AutoCAD saves either the full path (drive name, directory structure, file name), relative path (the location of the XREF relative to the host drawing, file name), or none (just the file name). 

TIP#1:   If you want to know what layer, linetype, etc, an object on an XREF is, use the command XLIST: it returns object information without opening the XREF file!

TIP #2:  NCOPY allows copying of selected objects in an XREF directly into your drawing!