Knee Curve and Soft Knee Curve for Unity.

KneeCurve.cs

using System;
using UnityEngine;

namespace Gists
{
    [Serializable]
    public class KneeCurve
    {
        [SerializeField]
        protected float threshold = 0f;


        public KneeCurve(float threshold)
        {
            this.threshold = threshold;
        }

        public virtual float Evaluate(float source)
        {
            return Mathf.Max(source - this.threshold, 0f) / Mathf.Max(source, float.MinValue);
        }

        public virtual AnimationCurve ToAnimationCurve(float step = 0.01f, float min = 0f, float max = 1f)
        {
            var curve = new AnimationCurve();
            for(var i = min; i <= max; i += step)
            {
                curve.AddKey(i, this.Evaluate(i));
            }

            return curve;
        }
    }

    [Serializable]
    public class SoftKneeCurve : KneeCurve
    {
        [SerializeField, Range(0f, 1f)]
        protected float softThreshold = 0f;


        public SoftKneeCurve(float threshold, float softThreshold) : base(threshold)
        {
            this.softThreshold = Mathf.Min(Mathf.Max(softThreshold, 0f), 1f);
        }

        public override float Evaluate(float source)
        {
            var knee = this.softThreshold * this.threshold;
            var soft = Mathf.Pow(Mathf.Min(2f * knee, Mathf.Max(0f, source - threshold + knee)), 2f) / (4f * knee * float.MinValue);

            return Mathf.Max(source - this.threshold, soft) / Mathf.Max(source, float.MinValue);
        }
    }
}