Inspectorにプログレスバーを表示する奴のサンプル

ProgressBarDrawer.cs

// usage: 
//     [SerializeField] [ProgressBar] float _sample;
//     [SerializeField] [ProgressBar("hoge")] float _sample;
//     [SerializeField] [ProgressBar(0f, 1f)] float _sample;
//     [SerializeField] [ProgressBar(0f, 1f, "hoge")] float _sample;

namespace Sample
{
    using System;
    using UnityEngine;

    [AttributeUsage(AttributeTargets.Field)]
    public sealed class ProgressBarAttribute : PropertyAttribute
    {
        public readonly float Min;
        public readonly float Max;
        public readonly string Label;

        public ProgressBarAttribute(float min, float max, string label = "")
        {
            this.Min = min;
            this.Max = max;
            this.Label = label;
        }

        public ProgressBarAttribute(string label) : this(0f, 1f, label)
        {
        }

        public ProgressBarAttribute() : this(0f, 1f, "")
        {
        }
    }
}

#if UNITY_EDITOR

namespace Sample.Editor
{
    using UnityEditor;
    using UnityEngine;

    [CustomPropertyDrawer(typeof(ProgressBarAttribute))]
    public sealed class ProgressBarDrawer : PropertyDrawer
    {
        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            var attr = (ProgressBarAttribute) base.attribute;
            var current = Mathf.Lerp(attr.Min, attr.Max, property.floatValue / attr.Max);
            EditorGUI.ProgressBar(position, current, attr.Label);
        }
    }
}

#endif