When creating or editing drawings in AutoCAD, keeping objects in the correct position and maintaining their geometry can sometimes require extra work.
For example, you might create a rectangular shape only to find that moving one of its corners changes it into an irregular shape. Or you may have carefully created geometry that needs to remain parallel, perpendicular or tangent as you continue editing your drawing.
This is where Geometric Constraints in AutoCAD can help. Geometric Constraints allow you to control the relationships between objects, helping your geometry behave as intended even when changes are made.
You can apply individual constraints or use Auto Constrain to identify relationships automatically and speed up the process.
What Are Geometric Constraints in AutoCAD?
Geometric Constraints control the geometric relationships between objects or points within your drawing
Instead of relying purely on the original position of your geometry, you can tell AutoCAD that certain objects should always maintain a particular relationship. For example, you can constrain objects so that they remain:
- Parallel
- Perpendicular
- Horizontal
- Vertical
- Tangent
- Concentric
- Coincident
- Equal
Once a constraint has been applied, AutoCAD maintains that relationship when you make changes to the geometry. This can be particularly useful when you're creating geometry that needs to retain a specific shape throughout the design process.
Where to Find Geometric Constraints
You can access Geometric Constraints from the Parametric tab on the AutoCAD Ribbon.
Within the Geometric panel, you'll find the different constraint types available, along with tools for automatically applying and managing constraints.
If you're new to constraints, one of the easiest places to start is Auto Constrain.
How to Use Auto Constrain in AutoCAD
Rather than manually applying individual constraints to every part of your geometry, Auto Constrain can analyse selected objects and apply appropriate geometric relationships automatically.
To use it:
- Open the Parametric tab on the Ribbon.
- Find the Geometric panel.
- Select Auto Constrain.
- Select the objects you want to constrain.
- Press Enter.
AutoCAD will analyse the selected geometry and apply suitable constraints. For example, if you're working with a slot-shaped object, AutoCAD may identify relationships such as Tangent, Parallel and Horizontal.
Once those relationships have been applied, you can edit the geometry while maintaining the overall shape.
How to See Your Constraints
When a Geometric Constraint is applied, AutoCAD displays a small icon beside the affected geometry. These icons allow you to quickly identify which relationships have been applied.
If the drawing becomes too cluttered, you don't need to remove the constraints. You can simply hide the icons while keeping the constraints active.
The Show/Hide options within the Geometric panel allow you to control whether the constraint icons are displayed.
This can be particularly useful when working with more complex drawings containing several constrained objects.
How to Delete Geometric Constraints
Sometimes you may need to remove constraints from an object.
This is particularly useful when working with drawings created by somebody else. If geometry behaves unexpectedly when you try to edit it, hidden constraints could be responsible.
To remove them:
- Go to the Parametric tab.
- Locate Delete Constraints.
- Select the objects containing the constraints you want to remove.
- Press Enter
If you're unsure whether constraints have been applied, use Show All first. This will display the constraint icons and help you identify relationships that may be affecting your geometry. You can then decide whether to keep or remove them.
Control Which Constraints AutoCAD Applies
Auto Constrain can save a significant amount of time, but you might not always want AutoCAD to apply every possible relationship.
Applying too many constraints can make geometry more difficult to edit. Fortunately, you can control which constraint types of AutoConstrain uses.
While using Auto Constrain, open the Settings option. You can access this through Dynamic Input or by entering S at the Command Line.
Alternatively, open Constraint Settings from the Geometric panel and select the AutoConstrain tab. From here, you can choose which types of constraints AutoCAD is allowed to apply. For example, if you simply want a rectangle to maintain its right-angled corners, you could clear the available options and select only Perpendicular.
This gives you more control over how your geometry behaves without unnecessarily restricting it.
When Should You Use Geometric Constraints?
Geometric Constraints can be particularly helpful when you're working with objects that need to maintain specific relationships as your drawing develops.
Rather than repeatedly correcting geometry after making changes, constraints allow you to define how objects should behave from the beginning.
They can be useful for maintaining:
- Right angles
- Parallel edges
- Tangent curves
- Concentric circles and arcs
- Horizontal and vertical geometry
- Consistent geometric relationships
The key is to use constraints where they add value rather than applying them unnecessarily throughout your drawing.
Make AutoCAD Work Smarter for You
Geometric Constraints are one of those AutoCAD features that can easily be overlooked, but they can make editing drawings much more predictable.
Whether you apply individual constraints or use Auto Constrain to identify relationships automatically, they give you greater control over how your geometry responds to changes.
Just remember that constraints can also affect how existing drawings behave. If you're working with a drawing from another user and objects aren't editing as expected, checking for hidden Geometric Constraints is a useful troubleshooting step.
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