How To Add Bone Constraints In Blender

Learning how to animate characters or mechanical rigs often means learning how to add bone constraints in Blender. This step-by-step guide will walk you through the entire process, from the basics to practical examples, so you can control your rigs with precision and ease.

Constraints are like rules for your bones. They automate movements, saving you from manually keyframing every single motion. Whether you want a character’s eyes to always face a target or a piston to slide along a specific axis, constraints are the tool you need. Let’s get started.

Before we jump into the steps, it’s important to understand the two main ways to add a constraint. The method is the same whether you’re working on an armature in Object Mode or in Pose Mode, but the result can be different. We’ll focus on Pose Mode, as that’s where most animation happens.

What Are Bone Constraints?

Think of a bone constraint as a set of instructions. You tell a bone (the “constrained” bone) to behave in a certain way based on the location, rotation, or scale of another object or bone (the “target”). This creates predictable, reusable relationships in your animation rig.

Constrained Bone: The bone that receives and follows the constraint’s rules.
Target: The object or bone that influences the constrained bone’s behavior.
Influence: A slider (from 0.0 to 1.0) that controls how strong the constraint’s effect is. This can be animated!

Step-by-Step: Adding Your First Constraint

Let’s go through the universal process. We’ll use a simple “Damped Track” constraint as our first example, which makes a bone always point at a target.

Open your Blender project with an armature. Enter Pose Mode by selecting the armature and choosing it from the mode menu.
Select the bone you want to constrain. This is your “constrained bone.”
Go to the Properties Editor and click on the Bone Constraint tab. It looks like a little chain link icon.
Click the “Add Bone Constraint” dropdown menu. You’ll see a long list of constraint types organized by category.
Select “Damped Track” from the “Tracking” category. A new constraint panel will appear.
In the constraint panel, find the “Target” field. Click on the eyedropper icon and then click on another object in your scene, or click the object field to select an object from a list.
Set the Track Axis. This defines which axis of the bone should point toward the target. You might need to try X, Y, or -Z depending on your bone’s rotation.
You should now see the constrained bone instantly rotate to point at the target object. Move the target around to see the bone follow it.

Essential Constraint Types and Their Uses

Blender has many constraints. Here are some of the most essential ones you’ll use regularly.

Copy Location / Rotation / Scale

These are perhaps the most straightforward. They copy the transform properties of a target.

Use Case: Making a character’s hand perfectly grip a sword object. You’d use Copy Location and Copy Rotation on the hand bone, targeting the sword.
Tip: You can use the “Offset” checkbox to make the copy relative to the bone’s original rest position.

Inverse Kinematics (IK) Constraint

This is a powerhouse for character animation. It lets you position an entire chain of bones (like an arm or leg) by moving just the last bone in the chain (the “IK target”).

Select the bone at the end of the chain (e.g., the wrist bone).
Add an “Inverse Kinematics” constraint.
Set the Chain Length to the number of bones in the chain (e.g., 2 for an upper arm and forearm).
Now, when you move the wrist bone, the elbow and shoulder will rotate automatically to follow.

Track To (or Locked Track)

Similar to Damped Track, but offers more control. It locks one axis of the bone while allowing another axis to track the target. This is perfect for making eyes or camera rigs.

Child Of Constraint

Extremely powerful. It makes one bone the temporary “child” of another bone or object, but you can turn the influence on and off. This is ideal for having a character pick up and put down objects.

Stretch To Constraint

This makes a bone stretch its length to reach a target. Great for tentacles, tails, or cartoonish stretching limbs.

You can control the volume preservation and the axis of stretch.

A Practical Example: Rigging a Simple Robot Arm

Let’s apply what we’ve learned. We’ll rig a 3-bone robot arm (Base, Arm, Grabber) with constraints for clear movement.

Setup: Create three bones in a chain. Name them “Base”, “Arm”, and “Grabber”.
Base Rotation (Copy Rotation): Select the “Base” bone. Add a Copy Rotation constraint. For the target, create an empty object (like a Plain Axis) and place it above the base. Now, rotating the Empty will rotate the entire arm structure.
Arm Piston (Limit Distance): We want the “Arm” bone to slide out only so far. Select the “Arm” bone. Add a Limit Distance constraint. Target the “Base” bone. Set the distance limit. Choose “Limit Mode” to “Limit on Inside” or “Outside” depending on your need. This creates a piston-like range of motion.
Grabber Tracking (Damped Track): Select the “Grabber” bone. Add a Damped Track constraint. Create a new target object (like a sphere) for it to point at. Move the sphere around; the grabber should always point at it.
Final Polish (Transforms): You can now animate the Empty (to rotate the base), the Arm bone’s location (to extend the piston), and the target sphere (to aim the grabber). All movements are clean and controlled by constraints.

Common Problems and How to Fix Them

Constraints can sometimes act strangely. Here are quick fixes for common issues.

Constraint Appears Broken or Has No Effect

Check your mode: Are you in Pose Mode? Constraints only visibly affect bones in Pose Mode.
Check the Influence: Is the Influence slider set to 1.0? If it’s at 0, the constraint is off.
Check the Target: Is the target field correctly set to the intended object or bone? The name should be there.

Bone Moves in the Wrong Direction

This is almost always an axis issue. Constraints use local bone axes.

In Edit Mode, select the bone and look at its axes. The yellow arrow is the bone’s “head” direction.
In the constraint panel, try different settings for the Axis (like -X instead of X, or switch to the Y axis).

Multiple Constraints Fighting Each Other

The order of constraints in the stack matters. Blender applies them from top to bottom.

In the bone’s constraint tab, you’ll see a list of all its constraints.
Use the up and down arrows on the right side of each constraint panel to reorder them.
Generally, IK constraints should be near the bottom, and Copy Transforms near the top, but it depends on your goal.

Animating Constraint Influence

The “Influence” slider is your key to dynamic rigs. You can keyframe it to turn constraints on and off over time.

With your bone selected in Pose Mode, find the constraint you want to animate.
At frame 1, with Influence at 0, hover your mouse over the Influence slider and press I to insert a keyframe.
Move to a later frame (e.g., frame 30). Change the Influence slider to 1.0. Press I over the slider again to set a second keyframe.
Now, between frames 1 and 30, the constraint will gradually become active. This is perfect for a character locking onto a target or releasing an object.

Advanced Tips: Using Space Switching

“Space” refers to the coordinate system a constraint uses. You can set a constraint to work in World Space, Local Space, or relative to another object’s space. This is a advanced but crucial concept for clean rigs.

World Space: The constraint uses the global scene coordinates.
Local Space (Owner): The constraint uses the constrained bone’s own local coordinates.
Local Space (Target): The constraint uses the target object’s local coordinates.
Example: A Copy Location constraint set to “Local Space (Target)” will make the bone follow the target’s location, but relative to the target’s own rotation and scale. This is often more predictable than World Space.

FAQ Section

How do you add constraints to bones in Blender?

Select a bone in Pose Mode, go to the Bone Constraints tab in the Properties editor (chain link icon), and click “Add Bone Constraint.” Then choose the type of constraint you need from the list.

What is the shortcut for adding constraints in Blender?

There isn’t a universal default shortcut. The fastest way is to select your bone, press F3 to open the search menu, and type the name of the constraint (like “Copy Location”). This will add it directly.

Why are my Blender bone constraints not working?

The top three reasons are: 1) You’re not in Pose Mode, 2) The Influence is set to 0, or 3) The Target field is empty or pointing to the wrong object. Also, check the constraint order if you have multiple constraints on one bone.

Can I copy a constraint from one bone to another?

Yes! In the Bone Constraints tab, each constraint panel has a “Copy to Selected” button (two squares icon). Select the bone with the constraint, then shift-select other bones, and click this button to copy it to all selected bones.

What’s the difference between a constraint and a driver?

A constraint typically links a bone’s transform to another object’s transform. A driver uses a custom property, a bone’s transform, or other data to control any numerical value in Blender, like an influence slider or a bone property. They are often used together for complex rigs.

Final Thoughts on Blender Bone Constraints

Mastering how to add bone constraints in Blender is a fundamental skill for any rigger or animator. They move you beyond simple keyframing into the realm of procedural, controlled, and efficient animation. Start with the basic Copy and Track constraints, then experiment with IK and the Child Of constraint. Don’t be afraid to stack them and animate their influence—this is where truly lifelike and responsive rigs come to life. Remember, the constraint stack order is important, and always test your rig thoroughly before starting a long animation. With practice, you’ll find constraints to be an indispensable part of your Blender workflow.