TrailRenderer.widthCurve

Description

Set the curve describing the width of the trail at various points along its length.

This property is multiplied by TrailRenderer.widthMultiplier to get the final width of the trail.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    public float width = 1.0f;
    public bool useCurve = true;
    private TrailRenderer tr;

    void Start()
    {
        tr = GetComponent<TrailRenderer>();
        tr.material = new Material(Shader.Find("Sprites/Default"));
    }

    void Update()
    {
        AnimationCurve curve = new AnimationCurve();
        if (useCurve)
        {
            curve.AddKey(0.0f, 0.0f);
            curve.AddKey(1.0f, 1.0f);
        }
        else
        {
            curve.AddKey(0.0f, 1.0f);
            curve.AddKey(1.0f, 1.0f);
        }

        tr.widthCurve = curve;
        tr.widthMultiplier = width;
        tr.transform.position = new Vector3(Mathf.Sin(Time.time * 1.51f) * 7.0f, Mathf.Cos(Time.time * 1.27f) * 4.0f, 0.0f);
    }

    void OnGUI()
    {
        GUI.Label(new Rect(25, 20, 200, 30), "Width");
        width = GUI.HorizontalSlider(new Rect(125, 25, 200, 30), width, 0.1f, 1.0f);
        useCurve = GUI.Toggle(new Rect(25, 65, 200, 30), useCurve, "Use Curve");
    }
}