FuelGauge.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

namespace NWH.VehiclePhysics
{
    public class FuelGauge : MonoBehaviour
    {
        /// <summary>
        /// Value at the end of needle travel, at the end angle.
        /// </summary>
        [Tooltip("Value at the end of needle travel, at the end angle.")]
        public float maxValue;

        /// <summary>
        /// Angle of the needle at the lowest value. You can use lock at start option to adjust this value while in play mode.
        /// </summary>
        [Tooltip("Angle of the needle at the lowest value. You can use lock at start option to adjust this value while in play mode.")]
        public float startAngle = 90f;

        /// <summary>
        /// Angle of the needle at the highest value. You can use lock at end option to adjust this value while in play mode.
        /// </summary>
        [Tooltip("Angle of the needle at the highest value. You can use lock at end option to adjust this value while in play mode.")]
        public float endAngle = 0f;

        /// <summary>
        /// Smooths the travel of the needle making it more inert, as if actually had some mass and resistance.
        /// </summary>
        [Tooltip("Smooths the travel of the needle making it more inert, as if actually had some mass and resistance.")]
        [Range(0, 1)]
        public float needleSmoothing;

        /// <summary>
        /// Locks the needle position at the start angle.
        /// </summary>
        [Tooltip("Locks the needle position at the start angle.")]
        public bool lockAtStart = false;

        /// <summary>
        /// Locks the needle position at the end angle.
        /// </summary>
        [Tooltip("Locks the needle position at the end angle.")]
        public bool lockAtEnd = false;

        private GameObject needle;
        private float currentValue;
        private float angle;
        private float prevAngle;
        private float percent;

        public float Value
        {
            get
            {
                return currentValue;
            }
            set
            {
                currentValue = Mathf.Clamp(value, 0, maxValue);
            }
        }

        private void Awake()
        {
            needle = transform.Find("Needle").gameObject;
        }

        private void Start()
        {
            angle = startAngle;
        }

        void Update()
        {
            percent = Mathf.Clamp01(currentValue / maxValue);
            prevAngle = angle;
            angle = Mathf.Lerp(startAngle + (endAngle - startAngle) * percent, prevAngle, needleSmoothing);

            if (lockAtEnd) angle = endAngle;
            if (lockAtStart) angle = startAngle;

            needle.transform.eulerAngles = new Vector3(needle.transform.eulerAngles.x, needle.transform.eulerAngles.y, angle);
        }
    }
}