Dimensions in ACA

March 19th, 2014

Dimensioning is simply the process of adding measurement annotation to a drawing.  Dimensions can be created for a variety of object types in many orientations.  The basic types of dimensioning are Linear, Radial, Angular, Ordinate, and Arc Length.  Linear dimensions can be horizontal, vertical, aligned, rotated, baseline or continued (chained). 

With more than 70 dimensioning-oriented settings in the Dimension Styles Manager, you can control nearly every aspect of the appearance of dimensions.  If you save your dimension styles in a drawing template (dwt) file, they will be available every time you start a new drawing.  To simplify drawing organization and dimension scaling, it is recommended that you create dimensions on layouts rather than in model space.

In addition to traditional AutoCAD dimensioning, AutoCAD® Architecture provides more intelligent and automated AEC Dimension objects.  Thoughtful creation of AEC dimension styles can greatly improve productivity during the construction documents phase of a project.  Another benefit of AEC dimension styles is that as AEC objects, they can be controlled with the AutoCAD Architecture display system and can be scale-dependent.  The same AEC dimension can be used for any number of scales in the drawing.

Dimensions can be associative, non-associative, or exploded.  Dimension associativity defines the relationship between geometric objects and the dimensions that give their distance and angles. There are three types of associativity between geometric objects and dimensions.

  • Associative dimensions automatically adjust their locations, orientations and measurement values when the geometric objects associated with them are modified.  These are created when the DIMASSOC system variable is set to 2.
  • Non-associative dimensions are selected and modified with the geometry they measure.  Non-associative dimensions do not change when the geometric objects they measure are modified.  These are created when the DIMASSOC system variable is set to 1.
  • Exploded dimensions contain a collection of separate objects, rather than a single dimension object.  These are created when the DIMASSOC system variable is set to 0.

A dimension is considered partially associative when only one end of the dimension is associated with a geometric object.  You can use the DIMREASSOCIATE command to reassociate non-associative dimensions.  Dimensions associated to model drawing views may lose their associativity if the drawing is opened and re-saved in a pre-2012 release of AutoCAD®.

Create a Dimension Style

A dimension style is a named collection of dimension settings that controls the appearance of dimensions, such as arrowhead style, text location, and lateral tolerances.  You can create dimension styles to specify the format of dimensions quickly and to ensure that dimensions conform to industry or project standards. 

When you create a dimension, it uses the settings of the current dimension style.  If you change a setting in a dimension style, all dimensions in the drawing that use the style update automatically.  You can create dimension substyles that use specified settings for different types of dimensions.  You can override a dimension style with dimension settings that deviate from the current dimension style.

To create a dimension style, begin by clicking the Home tab on the ribbon, Annotation panel, then select Dimension Style.  In the Dimension Style Manager, click New.  In the Create New Dimension Style dialog box, enter a name for the new dimension style and click Continue.  In the New Dimension Style dialog box (Figure 1), click each tab and make any changes for the new dimension style.  Click OK and then Close to exit the Dimension Style Manager.

Figure 1: New dimension style

Dynamic Dimensions

When you use grips to change the dimension or angle of an object, temporary dimension objects show you the changes you are making.  You can use Dynamic Input to enter a precise value instead of moving a grip.  This is active by default and selecting a grip displays a text box in which you can enter the desired value for the associated dimension or angle.  Click Dynamic Input on the application status bar to toggle this off.  Three types of dynamic dimensions display on grips:

  • Focal dimensions display highlighted in a white rectangular box.  If you type a value while a dynamic dimension is focused, the edit box is displayed at the dimension text location.
  • Editable dimensions display based on the drafting settings you specify.  If you press TAB while a dynamic dimension is focused, the dimension focus shifts forward to the next editable dimension.
  • Non-editable dimensions display in black text.  These dimensions typically display the current value of a property that you can modify with a grip.

You can apply different settings, such as the color of the dynamic dimension text box, on the Dynamic Input tab in the Drafting Settings dialog box (see Figure 2).  You can select the color of grips and the dynamic dimension linetype on the AEC Editor tab in Options.  It is important to note that when a dimension edit box is displayed, pressing Enter sets the value of the property that you are editing and ends the grip operation.  Pressing Tab sets the value, changes the focused dimension, and continues the same grip-editing operation.

Figure 2: Dynamic input appearance

AEC Dimensions

In AutoCAD Architecture, you can dimension object points specified in the AEC dimension style, points on objects picked in the drawing, or user-specified points in the drawing.  AEC dimensions associated with objects update when the object changes.  User-specified points are not associative and have to be changed manually if necessary.  An AEC dimension can contain both associative and non-associative points.  For example, you can create an AEC dimension that dimensions a wall, a multi-view block representing a floor drain, and user-specified points selected anywhere in the drawing.

When you select an AEC dimension, various grips are displayed.  You can use the grips to add and remove dimension points, move dimension chains, change the offset of extension lines and override wall component dimensions.  When dimensioning wall components, you have the option of using the center of the component or either side as the dimension point. You can also dimension wall components according to their structural function.  Grips for the individual component dimension points allow you to override style-defined dimension points on walls to accommodate special cases.  The dimension values in an AEC dimension are calculated from the actual current dimensions of associated objects.  You can override a value with a manually inserted value. 

The AEC dimension style defines objects to dimension in the AEC dimension and the display of the AEC dimension.  You can create and edit AEC dimension styles, import and export AEC dimension styles between drawings and purge AEC dimension styles that are not in use.  When you create, purge, import, export or edit styles, you access the Style Manager.  The Style Manager provides a central location in AutoCAD Architecture where you can work with styles from multiple drawings and templates.

You can create an AEC dimension tool from any AEC dimension style.  You can drag the style from the Style Manager onto a tool palette.  You can then specify default settings for any AEC dimensions created from the tool.  To create an AEC dimension, begin by clicking the Annotate tab on the ribbon, Dimensions panel (see Figure 3), and select one of the available dimension tools there.  Select the objects or points you want to dimension and press Enter.  Click where you want to insert the AEC dimension.

There are a few best practices for AEC Dimension Styles to keep in mind.

  • Make your dimension styles scale dependent where possible by using different AutoCAD dimension styles with different settings for “Overall Scale.” By changing display configurations, you can use a different display representation for dimension styles that adjusts to different scales and detail levels.
  • It is not necessary to store AEC Dimension styles or the AutoCAD dimension styles on which they are dependent for display in the template drawing.  Instead, you can use the tool properties to import them as needed from a style library. 
  • If you have configured the “Dimension” and “Type” parameters of your wall style components, you should take advantage of this in the AEC Dimension’s “Content” settings for the “Wall Width” dimension parameters by specifying “From Style” or “Structural from Style.”

Figure 3: Dimension panel

Dimensioning a Project

In the documentation phase of a project, you create detailed dimensions of objects.  AEC dimensions can be attached to objects in a drawing or to objects in an external reference.  You can dimension objects in source drawings such as elements or constructs, or you can dimension them in higher-level drawings such as views or sheets.

Begin by opening the project drawing in which to add a dimension.  This may not be the drawing in which the object to be dimensioned is located.  It may be a drawing that references the object.  Open the tool palette that you want to use and select an AEC dimension tool.  On the Properties palette, expand Basic General and select a style.  In the drawing area, select the objects to dimension and press Enter.  Specify the position of the new dimension.

  • If you want to insert the dimension group parallel to or perpendicular to the dimensioned object, then drag the cursor in the desired direction and click in the drawing at the desired insertion point.
  • If you want to insert the dimension group at a specified rotation, then enter “r” (Rotation) on the command line and press Enter.  Then enter a rotation angle, press enter and click in the drawing at the desired insertion point.
  • If you want to insert the dimension group aligned parallel to an object other than the dimensioned object, enter “a” (Align) on the command line and press Enter.  Then select the object in which to align the dimension group.  Press Enter and click in the drawing at the desired insertion point.

Converting AutoCAD Dimension to an AEC Dimension

For each AutoCAD dimension point, a non-associative AEC dimension point is created.  The resulting AEC dimension has the properties of the AEC dimension tool you select.  You can edit these properties after creating the AEC dimension. 
To do this, open the tool palette you want to use, right-click an AEC dimension tool, and click Apply Tool Properties to, then select AutoCAD Dimension (see Figure 4).  Select the AutoCAD dimensions and press Enter.  Specify the position of the AEC dimension by clicking the desired position in the drawing.  The AEC dimension can be placed above or below the object.   Drag the mouse to set the direction of the dimension.  The extension lines are drawn into the opposite direction. 

It is important to note that the angle you specify here is calculated in relation to the UCS and not to the dimensioned object.  When prompted to erase the original AutoCAD dimension, press Enter to keep the AutoCAD dimension or enter y (Yes) to erase it.  If you selected only one AutoCAD dimension, then the new AEC dimension is inserted at the same position as the AutoCAD dimension.  If you selected more than one AutoCAD dimension, then the new AEC dimension is inserted according to your specifications.

Figure 4: Convert to AEC dimension

Modifying Dimension Text

After you create a dimension, you can move, rotate, or replace the dimension text.  You can move the text to a new location or back to its home position, which is the position defined by the current dimension style.  You can move dimension text to the left, right, or center along the dimension line or to any position inside or outside the extension lines.  A quick and simple way to do this is by using grips.  If you move text up or down, the current vertical alignment of the text relative to the dimension line is not changed, so the dimension and extension lines are modified accordingly.

Hover over a dimension text grip to quickly access the following functionality:

  • Stretch – This is the default grip behavior.  If the text is positioned on the dimension line, Stretch moves the dimension line farther away or closer to the object being dimensioned.  If the text is positioned away from the dimension line, with or without a leader, Stretch moves the text without moving the dimension line.
  • Move with Dim Line – Positions text on the dimension line and moves the dimension line farther away or closer to the object being dimensioned.
  • Move Text Only – Positions the dimension text without moving the dimension line.
  • Move with Leader – Positions the dimension text with a leader line to the dimension line.
  • Above Dim Line – Positions the dimension text above the dimension line (left of the dimension line for vertical dimensions).
  • Center Vertically – Positions the dimension text so the dimension line cuts through the vertical center of the text.
  • Reset Text Position – Positions the dimension text back to its default position based on the active dimension style.

Clicking on an AEC dimension brings up the AEC Dimension tab on the ribbon, which allows for many editing capabilities (see Figure 5).  If you wish to return the dimension text back to its original location, select the dimension text, hover over the text grip, and click Reset Text Position.

Figure 5: Modify dimension

Conclusion

Dimensioning in AutoCAD Architecture contains many capabilities to ensure quality, accurate measurements within your drawing.  There is a lot you can do with dimensions, so take a few minutes to sit down and explore all the capabilities.  You may be surprised at all you can do!

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About the Authors

Melinda Heavrin

Melinda Heavrin

Melinda Heavrin is a CAD Coordinator & Facility Planner for Norton Healthcare in Louisville, Kentucky.  She has been using AutoCAD Architecture since release 2000.  Melinda can be reached for comments and questions at melinda.heavrin@nortonhealthcare.org.

 

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