ParticleSystem.TrailModule.minVertexDistance

Description

Set the minimum distance each trail can travel before a new vertex is added to it.

Smaller values with give smoother trails, consisting of more vertices, but costing more performance.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    public float hSliderValueDistance = 0.2f;

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

        var main = ps.main;
        main.startColor = new ParticleSystem.MinMaxGradient(Color.red, Color.yellow);
        main.startSize = 0.1f;
        main.startLifetime = 2.5f;
        main.gravityModifier = 0.35f;

        var trails = ps.trails;
        trails.enabled = true;

        var psr = GetComponent<ParticleSystemRenderer>();
        psr.trailMaterial = new Material(Shader.Find("Sprites/Default"));
    }

    void Update()
    {
        var trails = ps.trails;
        trails.minVertexDistance = hSliderValueDistance;
    }

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

        hSliderValueDistance = GUI.HorizontalSlider(new Rect(125, 45, 100, 30), hSliderValueDistance, 0.01f, 1.0f);
    }
}