Fix: Unity Cinemachine Impulse Listener Not Shaking

Here is how to fix Cinemachine Impulse Listener not shaking when the source generates a signal. You set up an Impulse Source on an explosion prefab, attach a CinemachineImpulseListener to your virtual camera, and call GenerateImpulse. Nothing happens. The console shows no errors, the source thinks it fired, but the camera holds perfectly still. Almost always, the channel mask, the signal asset, or the listener gain is the culprit.

The Symptom

An CinemachineImpulseSource calls GenerateImpulse on a hit event. The callback runs, no exceptions are thrown, the impulse profiler shows a signal was generated — but the active virtual camera does not move. Other camera shake systems (like Cinemachine Basic Multi Channel Perlin) work correctly, so the camera setup itself is fine.

What Causes This

Channel mismatch. Each impulse source broadcasts on a channel; each listener subscribes to a channel mask. If your source is on channel 4 but your listener listens only to channel 1, the signal is filtered out. Channel masks are bitwise, so subscribing to multiple channels requires combining flags.

No Raw Signal asset. The Impulse Source has a Raw Signal field that points to an ImpulseSignal asset (a curve over time). If this is empty, the source generates a zero-amplitude signal. Cinemachine ships with several presets like 6D Shake and Recoil.

Listener Gain is zero. The listener has a Gain multiplier applied to incoming signals. If it is set to 0, every signal is multiplied to nothing.

Source out of range. Impulse signals decay with distance. If the source is far from the camera and the source’s Impact Radius and Dissipation Distance are small, the camera receives an attenuated signal that is too weak to see.

The Fix

Step 1: Verify channel match. Open the Impulse Source and the Impulse Listener inspectors side by side. The source has a Channel dropdown. The listener has a Channel Mask. Both should include at least one common channel.

Step 2: Assign a Raw Signal. On the Impulse Source, drag a signal asset into the Raw Signal field. Use the Cinemachine’s built-in 6D Shake as a starting point.

Step 3: Generate the impulse with explicit force.

using UnityEngine;
using Unity.Cinemachine;

[RequireComponent(typeof(CinemachineImpulseSource))]
public class ExplosionShake : MonoBehaviour
{
    private CinemachineImpulseSource source;

    void Awake() { source = GetComponent<CinemachineImpulseSource>(); }

    public void Boom(float magnitude = 1f)
    {
        // Pass a velocity vector for directional shake
        Vector3 velocity = Random.insideUnitSphere * magnitude;
        source.GenerateImpulseWithVelocity(velocity);
    }
}

Step 4: Confirm listener Gain. On the CinemachineImpulseListener, set Gain to 1.0 for a baseline. Also confirm Use 2D Distance matches your project (enable for top-down 2D games so depth differences do not attenuate the signal).

Step 5: Tune dissipation.

// In the source inspector or via code:
source.ImpulseDefinition.ImpactRadius = 5f;
source.ImpulseDefinition.DissipationDistance = 100f;
source.ImpulseDefinition.DissipationRate = 0.25f;

A small radius means the camera must be very close to feel the full force. A large dissipation distance means the signal travels far before decaying. For first-person games where the source and camera are usually nearby, set Impact Radius to roughly the player’s effective range.

Verifying the Pipeline

Drop a quick debug log on each end:

// Subscribe to listener events
void OnEnable()
{
    listener.RegisterCallback((Vector3 pos, Quaternion rot) => {
        if (pos.sqrMagnitude > 0.0001f) Debug.Log($"Got impulse: {pos}");
    });
}

If you see logs but no visible motion, the signal is too small — raise gain. If you see no logs at all, the channel or signal asset is wrong.

“Channels match, signal assigned, gain non-zero, source within dissipation range. Four checks, in order, every time.”

Related Issues

For other Cinemachine motion problems, see Cinemachine Camera Jitter and Cinemachine Camera Shaking.

Channels are silent when they mismatch. Check both ends.