Root motion in Unity - Step-by-Step Execution

Concept Flow - Root motion

Animator plays animation clip

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Animation contains root motion data

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Extract root motion delta position & rotation

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Apply root motion to GameObject transform

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GameObject moves/rotates in scene

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Next frame

Root motion means the animation moves the character by changing its position and rotation, not just playing visuals.

Execution Sample

Unity

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

This code applies the root motion delta from the animation to the GameObject's position and rotation each frame.

Execution Table

Step	Animator deltaPosition	Animator deltaRotation	Transform.position before	Transform.rotation before	Action	Transform.position after	Transform.rotation after
1	(0.1, 0, 0)	Quaternion.Euler(0, 5, 0)	(0, 0, 0)	Quaternion.Euler(0, 0, 0)	Apply deltaPosition and deltaRotation	(0.1, 0, 0)	Quaternion.Euler(0, 5, 0)
2	(0.2, 0, 0)	Quaternion.Euler(0, 10, 0)	(0.1, 0, 0)	Quaternion.Euler(0, 5, 0)	Apply deltaPosition and deltaRotation	(0.3, 0, 0)	Quaternion.Euler(0, 15, 0)
3	(0, 0, 0)	Quaternion.identity	(0.3, 0, 0)	Quaternion.Euler(0, 15, 0)	No movement in animation	(0.3, 0, 0)	Quaternion.Euler(0, 15, 0)
4	(0.15, 0, 0)	Quaternion.Euler(0, -5, 0)	(0.3, 0, 0)	Quaternion.Euler(0, 15, 0)	Apply deltaPosition and deltaRotation	(0.45, 0, 0)	Quaternion.Euler(0, 10, 0)
5	(0, 0, 0)	Quaternion.identity	(0.45, 0, 0)	Quaternion.Euler(0, 10, 0)	No movement in animation	(0.45, 0, 0)	Quaternion.Euler(0, 10, 0)

💡 Animation frames end or no more root motion data to apply

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5
transform.position	(0, 0, 0)	(0.1, 0, 0)	(0.3, 0, 0)	(0.3, 0, 0)	(0.45, 0, 0)	(0.45, 0, 0)
transform.rotation	Quaternion.Euler(0, 0, 0)	Quaternion.Euler(0, 5, 0)	Quaternion.Euler(0, 15, 0)	Quaternion.Euler(0, 15, 0)	Quaternion.Euler(0, 10, 0)	Quaternion.Euler(0, 10, 0)
animator.deltaPosition	(0, 0, 0)	(0.1, 0, 0)	(0.2, 0, 0)	(0, 0, 0)	(0.15, 0, 0)	(0, 0, 0)
animator.deltaRotation	Quaternion.identity	Quaternion.Euler(0, 5, 0)	Quaternion.Euler(0, 10, 0)	Quaternion.identity	Quaternion.Euler(0, -5, 0)	Quaternion.identity

Key Moments - 3 Insights

Why does the GameObject move even though we only play an animation?

Because the animation contains root motion data that changes position and rotation, which we apply to the GameObject's transform as shown in the execution_table steps.

What happens if animator.deltaPosition is zero but deltaRotation is not?

The GameObject will rotate but not move in position.

Why do we multiply transform.rotation by deltaRotation instead of adding?

Rotations are combined by multiplication of quaternions to keep correct orientation, as shown in the execution_table rotation updates.

Visual Quiz - 3 Questions

Look at the execution_table, what is transform.position after step 2?

A (0.2, 0, 0)

B (0.3, 0, 0)

C (0.1, 0, 0)

D (0, 0, 0)

💡 Hint

Check the 'Transform.position after' column in row for step 2.

At which step does the animator.deltaPosition have no movement?

A Step 3

B Step 1

C Step 4

D Step 2

💡 Hint

Look at the 'Animator deltaPosition' column for zero vector.

If we skip applying animator.deltaRotation, what happens to transform.rotation after step 1?

A It becomes Quaternion.identity

B It becomes Quaternion.Euler(0, 5, 0)

C It stays at Quaternion.Euler(0, 0, 0)

D It becomes Quaternion.Euler(0, 10, 0)

💡 Hint

Refer to how transform.rotation changes by multiplying deltaRotation in execution_table.

Concept Snapshot

Root motion means the animation moves the character's position and rotation.
Use OnAnimatorMove() to apply animator.deltaPosition and animator.deltaRotation.
Apply deltaPosition by adding to transform.position.
Apply deltaRotation by multiplying transform.rotation.
This makes the GameObject move naturally with the animation.

Full Transcript

Root motion in Unity means the animation clip contains movement data that changes the GameObject's position and rotation. Instead of just playing visuals, the animation moves the character in the scene. The key method is OnAnimatorMove(), where we take the animator's deltaPosition and deltaRotation and apply them to the GameObject's transform. This is done by adding deltaPosition to transform.position and multiplying deltaRotation with transform.rotation. The execution table shows step-by-step how these values change each frame, moving and rotating the GameObject. Beginners often wonder why the object moves without explicit code; it's because of root motion data in the animation. Also, rotations combine by multiplication, not addition, to keep orientation correct. Understanding this helps create smooth, realistic character movement driven by animations.