ParticleSystemRenderer.normalDirection

Description

Specifies how much a billboard particle orients its normals towards the Camera.

Set this to 0 to spherize billboard normals. Set this to 1 to points normals towards the Camera.

using UnityEngine;
using UnityEditor;
using System.Collections;

public class ExampleClass : MonoBehaviour {

    private ParticleSystem ps;
    private ParticleSystemRenderer psr;
    public float normalDirection = 1.0f;

    void Start() {

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

        psr.material = AssetDatabase.GetBuiltinExtraResource<Material>("Default-Diffuse.mat");
    }

    void Update() {

        psr.normalDirection = normalDirection;
    }

    void OnGUI() {

        normalDirection = GUI.HorizontalSlider(new Rect(25, 25, 100, 30), normalDirection, 0.0f, 1.0f);
    }
}