public float speedModifierMultiplier ;

Changing this property is more efficient than accessing the entire curve, if you only want to change the overall speed multiplier.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { private ParticleSystem ps; public float hSliderValueSpeed = 1.0f;

void Start() { ps = GetComponent<ParticleSystem>();

var velocityOverLifetime = ps.velocityOverLifetime; velocityOverLifetime.enabled = true; velocityOverLifetime.space = ParticleSystemSimulationSpace.World;

AnimationCurve curve = new AnimationCurve(); curve.AddKey(0.0f, 0.0f); curve.AddKey(1.0f, 1.0f);

ParticleSystem.MinMaxCurve minMaxCurve = new ParticleSystem.MinMaxCurve(1.0f, curve);

velocityOverLifetime.speedModifier = minMaxCurve; }

void Update() { var velocityOverLifetime = ps.velocityOverLifetime; velocityOverLifetime.speedModifierMultiplier = hSliderValueSpeed; }

void OnGUI() { GUI.Label(new Rect(25, 40, 100, 30), "Speed");

hSliderValueSpeed = GUI.HorizontalSlider(new Rect(55, 45, 100, 30), hSliderValueSpeed, -50.0f, 50.0f); } }