ParticleSystemRenderer.velocityScale

Description

How much are the particles stretched depending on "how fast they move".

Use this to make particles get longer as their speed increases.

no example available in JavaScript

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {

    private ParticleSystem ps;
    private ParticleSystemRenderer psr;
    public ParticleSystemRenderMode renderMode = ParticleSystemRenderMode.Billboard;
    public float cameraScale = 0.0f;
    public float lengthScale = 0.0f;
    public float velocityScale = 1.0f;

    void Start() {

        ps = GetComponent<ParticleSystem>();
        psr = GetComponent<ParticleSystemRenderer>();

        psr.mesh = Resources.GetBuiltinResource<Mesh>("Capsule.fbx");

        var main = ps.main;
        main.startSpeed = new ParticleSystem.MinMaxCurve(0.5f, 1.5f);
        main.startSize = new ParticleSystem.MinMaxCurve(0.1f, 0.8f);
    }

    void Update() {
        psr.renderMode = renderMode;
        psr.cameraVelocityScale = cameraScale;
        psr.lengthScale = lengthScale;
        psr.velocityScale = velocityScale;

        if (renderMode == ParticleSystemRenderMode.Stretch)
            Camera.main.transform.position = new Vector3(Mathf.Sin(Time.time) * 4.0f, 0.0f, -10.0f);    // move the camera so we can see the effect on stretch camera velocity
    }

    void OnGUI() {
        renderMode = (ParticleSystemRenderMode)GUI.SelectionGrid(new Rect(25, 25, 900, 30), (int)renderMode, new GUIContent[] { new GUIContent("Billboard"), new GUIContent("Stretch"), new GUIContent("HorizontalBillboard"), new GUIContent("VerticalBillboard"), new GUIContent("Mesh"), new GUIContent("None") }, 6);

        if (renderMode == ParticleSystemRenderMode.Stretch) {

            GUI.Label(new Rect(25, 80, 100, 30), "Camera Scale");
            GUI.Label(new Rect(25, 120, 100, 30), "Length Scale");
            GUI.Label(new Rect(25, 160, 100, 30), "Velocity Scale");

            cameraScale = GUI.HorizontalSlider(new Rect(125, 85, 100, 30), cameraScale, 0.0f, 10.0f);
            lengthScale = GUI.HorizontalSlider(new Rect(125, 125, 100, 30), lengthScale, 0.0f, 10.0f);
            velocityScale = GUI.HorizontalSlider(new Rect(125, 165, 100, 30), velocityScale, 0.0f, 10.0f);
        }
    }
}