Access the particle system force over lifetime module.
using UnityEngine; using System.Collections;
public class ExampleClass : MonoBehaviour { void Start() { ParticleSystem ps = GetComponent<ParticleSystem>(); var fo = ps.forceOverLifetime; fo.enabled = true;
AnimationCurve curve = new AnimationCurve(); curve.AddKey( 0.0f, 0.1f ); curve.AddKey( 0.75f, 1.0f ); fo.x = new ParticleSystem.MinMaxCurve(1.5f, curve); } }