# SetInfluence(int, ParticleSystemForceField)

> Assigns the Force Field at the given index in the influencers list.

## Definition

* **Type:** Method
* **Namespace:** [UnityEngine](/engine/6000.7/script-reference/unityengine.md)
* **Assembly:** UnityEngine.ParticleSystemModule

```csharp
public void SetInfluence(int index, ParticleSystemForceField field)
```

### Parameters

**** (\[int]\(https\://learn.microsoft.com/dotnet/api/system.int32)): Index to assign the Force Field.**** (\[ParticleSystemForceField]\(/engine/6000.7/script-reference/unityengine/particlesystemforcefield)): Force Field that to assign.

### Remarks

When [\_influenceFilter](/engine/6000.7/script-reference/unityengine/particlesystem/externalforcesmodule/influencefilter.md) is set to [ParticleSystemGameObjectFilter.List](/engine/6000.7/script-reference/unityengine/particlesystemgameobjectfilter/list.md) then only Force Fields in the influencers list affect the Particle System.

### Examples

```csharp
using UnityEngine;

public class Example : MonoBehaviour
{
    public ParticleSystem system;
    public ParticleSystemForceField field1;
    public ParticleSystemForceField field2;

    ParticleSystem.ExternalForcesModule m_ExternalForcesModule;

    void Start()
    {
        if (system == null)
        {
            Debug.LogError("Please assign a Particle System to `system`.");
            enabled = false;
            return;
        }

        if (field1 == null || field2 == null)
        {
            Debug.LogError("Please assign a ParticleSystemForceField to `field1` and `field2`.");
            enabled = false;
            return;
        }

        m_ExternalForcesModule = system.externalForces;
        m_ExternalForcesModule.enabled = true;
        m_ExternalForcesModule.influenceFilter = ParticleSystemGameObjectFilter.List;
        m_ExternalForcesModule.AddInfluence(field1);
    }

    void OnGUI()
    {
        Debug.Assert(m_ExternalForcesModule.influenceCount == 1);
        var currentForceField = m_ExternalForcesModule.GetInfluence(0);

        GUILayout.BeginHorizontal();
        GUILayout.Label("Influence: " + currentForceField.name);

        if (GUILayout.Button("Toggle"))
        {
            m_ExternalForcesModule.SetInfluence(0, currentForceField == field1 ? field2 : field1);
        }

        GUILayout.EndHorizontal();
    }
}
```