How to Use the Limit Distance Constraint in Blender

The Limit Distance constraint in Blender restricts the distance between an object (or bone) and a target object, keeping them within a specified radius. This article provides a straightforward guide on how to add this constraint, configure its primary distance modes, and apply it effectively in 3D modeling and animation workflows.

Step-by-Step Guide to Applying the Constraint

  1. Select the Object: In the 3D Viewport, click on the object or bone you want to restrict.
  2. Open Constraints: Go to the Properties Editor on the right side of the screen and click the Object Constraints tab (a blue icon with two connected links). If you are using an Armature in Pose Mode, select the Bone Constraints tab instead.
  3. Add Constraint: Click Add Object Constraint (or Add Bone Constraint) and select Limit Distance from the tracking section.
  4. Assign a Target: Click the Target field inside the constraint panel and select the object you want to measure the distance against.

Configuring Constraint Settings

Once the target is assigned, adjust the primary settings to control how the object behaves:

  • Distance: Defines the radius threshold (in Blender Units/meters) between the owner object and the target.
  • Limit Mode: Determines how the restriction is enforced:
    • Inside: The object can move freely within the distance radius but cannot move beyond it.
    • Outside: The object is kept out of the radius and cannot move closer than the defined distance.
    • Surface: The object is locked exactly onto the spherical boundary of the target at the specified distance.
  • Space: Sets the coordinate system (World Space, Local Space, etc.) used to evaluate the distance. In most standard setups, leaving this set to World Space works best.
  • Affect Transform: Enable this button if you want the constraint to directly update the owner's transform coordinates rather than just visually limiting its position in the viewport.

Testing the Constraint

Grab the restricted object by pressing G and move it around. Depending on your chosen Limit Mode, the object will either stop at the boundary, stay locked outside the perimeter, or slide along the spherical boundary centered on the target object.