Root motion in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable root motion on the Animator component.

Unity

Animator animator = GetComponent<Animator>();
animator.[1] = true;

Drag options to blanks, or click blank then click option'

AapplyRootMotionEnabled

BapplyRootMotion

CapplyRootMotionFlag

DapplyRootMotionTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent property name.

Trying to set root motion on the wrong component.

The correct property to enable root motion is applyRootMotion.

2fill in blank

medium

Complete the code to override root motion in the Animator by implementing the correct method.

Unity

void [1]() {
    // Custom root motion handling
}

Drag options to blanks, or click blank then click option'

AOnRootMotionApply

BOnRootMotionUpdate

COnAnimatorRoot

DOnAnimatorMove

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist in Unity's Animator callbacks.

Trying to override root motion in Update() instead.

The method OnAnimatorMove is called when root motion is applied and can be overridden for custom handling.

3fill in blank

hard

Fix the error in the code to correctly apply root motion delta to the transform.

Unity

void OnAnimatorMove() {
    transform.position += [1];
    transform.rotation *= animator.deltaRotation;
}

Drag options to blanks, or click blank then click option'

Aanimator.deltaPosition

Banimator.rootPosition

Canimator.positionDelta

Danimator.motionDelta

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent property like rootPosition or motionDelta.

Confusing deltaPosition with transform.position.

The correct property to get the root motion position change is animator.deltaPosition.

4fill in blank

hard

Fill both blanks to create a dictionary that maps animation clip names to their root motion curves.

Unity

Dictionary<string, AnimationCurve> rootMotionCurves = new Dictionary<string, AnimationCurve>() {
    { [1], [2] }
};

Drag options to blanks, or click blank then click option'

A"Run"

BrunCurve

C"Jump"

DjumpCurve

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names instead of strings for keys.

Swapping the key and value positions.

The key should be the animation clip name as a string, and the value should be the corresponding AnimationCurve variable.

5fill in blank

hard

Fill all three blanks to correctly update the Animator's root motion position and rotation in OnAnimatorMove.

Unity

void OnAnimatorMove() {
    Vector3 rootPos = transform.position + [1];
    Quaternion rootRot = transform.rotation * [2];
    transform.SetPositionAndRotation(rootPos, [3]);
}

Drag options to blanks, or click blank then click option'

Aanimator.deltaPosition

Banimator.deltaRotation

CrootRot

Dtransform.rotation

Attempts:

3 left

💡 Hint

Common Mistakes

Using transform.rotation instead of the combined rootRot.

Not adding deltaPosition to current position.

The root motion delta position and rotation are added to the current transform, then applied using SetPositionAndRotation.

Practice

1. What does enabling applyRootMotion on an Animator component do in Unity?

easy

A. It resets the character's position to the origin every frame.

B. It lets the animation control the character's movement automatically.

C. It makes the character move only by script, ignoring animations.

D. It disables all animations on the character.

Solution

1. Step 1: Understand the role of applyRootMotion

   Setting applyRootMotion to true allows the animation's movement data to move the character automatically.

2. Step 2: Compare with other options

   Other options describe disabling animations or ignoring root motion, which is incorrect.

3. Final Answer:

   It lets the animation control the character's movement automatically. -> Option B

4. Quick Check:

   applyRootMotion true = animation controls movement [OK]

Hint: Remember: applyRootMotion true means animation moves character [OK]

Common Mistakes:

• Thinking applyRootMotion disables animations
• Confusing root motion with scripted movement
• Assuming it resets position every frame

2. Which of the following is the correct way to enable root motion in a Unity Animator component via script?

easy

A. animator.applyRootMotion = true;

B. animator.rootMotion = true;

C. animator.enableRootMotion(true);

D. animator.setRootMotion(true);

Solution

1. Step 1: Recall the correct property name

   The Animator component uses the property applyRootMotion to enable root motion.

2. Step 2: Check syntax correctness

   Only animator.applyRootMotion = true; is valid C# syntax and correct property usage.

3. Final Answer:

   animator.applyRootMotion = true; -> Option A

4. Quick Check:

   Correct property = applyRootMotion [OK]

Hint: Use applyRootMotion property exactly as named [OK]

Common Mistakes:

• Using incorrect property names like rootMotion
• Trying to call methods instead of setting properties
• Syntax errors like missing semicolons

3. Given this code snippet in a Unity script attached to a character:

void OnAnimatorMove() {
    Vector3 rootPos = animator.rootPosition;
    rootPos.y = transform.position.y;
    transform.position = rootPos;
}

What is the effect of this code on the character's movement?

medium

A. The character moves only vertically according to the animation.

B. The character moves exactly as the animation's root motion in all directions.

C. The character ignores root motion and stays still.

D. The character moves following the animation's horizontal root motion but keeps its original vertical position.

Solution

1. Step 1: Analyze the code's position adjustment

   The code sets the character's position to the animation's root position but keeps the original Y (vertical) position.

2. Step 2: Understand the movement effect

   This means horizontal movement (X and Z) follows animation, but vertical movement stays unchanged.

3. Final Answer:

   The character moves following the animation's horizontal root motion but keeps its original vertical position. -> Option D

4. Quick Check:

   Y position unchanged, horizontal moves with root motion [OK]

Hint: Check which axes are changed in root motion code [OK]

Common Mistakes:

• Assuming full 3D root motion is applied
• Ignoring the line that keeps Y position fixed
• Thinking character stays still

4. You wrote this code to apply root motion in Unity:

void OnAnimatorMove() {
    transform.position = animator.rootPosition;
    transform.rotation = animator.rootRotation;
}

But the character does not move as expected. What is the likely problem?

medium

A. The Animator's applyRootMotion property is not enabled.

B. OnAnimatorMove should not be used for root motion.

C. You must call base.OnAnimatorMove() inside the method.

D. The transform cannot be set inside OnAnimatorMove.

Solution

1. Step 1: Check root motion enabling

   Root motion only works if applyRootMotion is true on the Animator component.

2. Step 2: Understand OnAnimatorMove usage

   Using OnAnimatorMove to override root motion is valid, but it requires applyRootMotion enabled.

3. Final Answer:

   The Animator's applyRootMotion property is not enabled. -> Option A

4. Quick Check:

   applyRootMotion must be true for root motion [OK]

Hint: Always enable applyRootMotion to use root motion overrides [OK]

Common Mistakes:

• Forgetting to enable applyRootMotion
• Thinking base.OnAnimatorMove() is required
• Believing transform can't be set in OnAnimatorMove

5. You want your character to move with root motion but only apply horizontal movement from the animation, while controlling vertical movement via physics (gravity). How should you modify OnAnimatorMove to achieve this?

hard

A. Set transform.position to animator.rootPosition but keep transform.position.y unchanged.

B. Set transform.position to animator.rootPosition and ignore vertical velocity.

C. Set transform.position to animator.rootPosition and add vertical velocity manually.

D. Do not override OnAnimatorMove; use applyRootMotion only.

Solution

1. Step 1: Understand the goal

   You want horizontal movement from root motion but vertical movement controlled by physics (like gravity velocity).

2. Step 2: Combine root motion with vertical velocity

   Override OnAnimatorMove to set horizontal position from root motion and add vertical velocity manually to Y position.

3. Step 3: Choose the correct approach

   Set transform.position to animator.rootPosition and add vertical velocity manually. describes adding vertical velocity manually, which matches the goal.

4. Final Answer:

   Set transform.position to animator.rootPosition and add vertical velocity manually. -> Option C

5. Quick Check:

   Combine root motion horizontal + manual vertical velocity [OK]

Hint: Add vertical velocity manually when overriding root motion [OK]

Common Mistakes:

• Keeping Y position unchanged ignores physics
• Ignoring vertical velocity causes unnatural movement
• Not overriding OnAnimatorMove loses control