Mathf.cs

// Unity C# reference source
// Copyright (c) Unity Technologies. For terms of use, see
// https://unity3d.com/legal/licenses/Unity_Reference_Only_License

using System;
//using System.Threading;
using System.Runtime.CompilerServices;
using System.Numerics;
using System.Collections.Generic;
using System.Linq;

namespace Mola
{
    // A collection of common math functions.
    public partial struct Mathf
    {
        public static float Remap(float value, float input1, float input2, float output1, float output2)
        {
            return (output2 - output1) * value / (input2 - input1) + output1;
        }
        
        /// <summary>
        /// Maps the values of a list from a minimum value to a maximum value.
        /// </summary>
        /// <param name="value"></param>
        /// <param name="toMin"></param>
        /// <param name="toMax"></param>
        /// <returns></returns>
        public static List<float> MapList(List<float> value, float toMin = 0, float toMax = 1)
        {
            float minValue = value.Min();
            float maxValue = value.Max();
            float delta = maxValue - minValue;
            float deltaTarget = toMax - toMin;
            List<float> toValue = value.Select(x => toMin + deltaTarget * (x - minValue) / delta).ToList();
            return toValue;
        }
        /// <summary>
        /// Maps a value from one range to another.
        /// </summary>
        /// <returns></returns>
        public static float Map(float value, float fromMin, float fromMax, float toMin, float toMax)
        {
            float delta = fromMax - fromMin;
            if (Math.Abs(delta) < 1.23E-7) return 0;
            return toMin + ((toMax - toMin) / delta) * (value - fromMin);
        }
        // Returns the sine of angle /f/ in radians.
        public static float Sin(float f) { return (float)Math.Sin(f); }

        // Returns the cosine of angle /f/ in radians.
        public static float Cos(float f) { return (float)Math.Cos(f); }

        // Returns the tangent of angle /f/ in radians.
        public static float Tan(float f) { return (float)Math.Tan(f); }

        // Returns the arc-sine of /f/ - the angle in radians whose sine is /f/.
        public static float Asin(float f) { return (float)Math.Asin(f); }

        // Returns the arc-cosine of /f/ - the angle in radians whose cosine is /f/.
        public static float Acos(float f) { return (float)Math.Acos(f); }

        // Returns the arc-tangent of /f/ - the angle in radians whose tangent is /f/.
        public static float Atan(float f) { return (float)Math.Atan(f); }

        // Returns the angle in radians whose ::ref::Tan is @@y/x@@.
        public static float Atan2(float y, float x) { return (float)Math.Atan2(y, x); }

        // Returns square root of /f/.
        public static float Sqrt(float f) { return (float)Math.Sqrt(f); }

        // Returns the absolute value of /f/.
        public static float Abs(float f) { return Math.Abs(f); }

        // Returns the absolute value of /value/.
        public static int Abs(int value) { return Math.Abs(value); }

        /// *listonly*
        public static float Min(float a, float b) { return a < b ? a : b; }
        // Returns the smallest of two or more values.
        public static float Min(params float[] values)
        {
            int len = values.Length;
            if (len == 0)
                return 0;
            float m = values[0];
            for (int i = 1; i < len; i++)
            {
                if (values[i] < m)
                    m = values[i];
            }
            return m;
        }

        /// *listonly*
        public static int Min(int a, int b) { return a < b ? a : b; }
        // Returns the smallest of two or more values.
        public static int Min(params int[] values)
        {
            int len = values.Length;
            if (len == 0)
                return 0;
            int m = values[0];
            for (int i = 1; i < len; i++)
            {
                if (values[i] < m)
                    m = values[i];
            }
            return m;
        }

        /// *listonly*
        public static float Max(float a, float b) { return a > b ? a : b; }
        // Returns largest of two or more values.
        public static float Max(params float[] values)
        {
            int len = values.Length;
            if (len == 0)
                return 0;
            float m = values[0];
            for (int i = 1; i < len; i++)
            {
                if (values[i] > m)
                    m = values[i];
            }
            return m;
        }

        /// *listonly*
        public static int Max(int a, int b) { return a > b ? a : b; }
        // Returns the largest of two or more values.
        public static int Max(params int[] values)
        {
            int len = values.Length;
            if (len == 0)
                return 0;
            int m = values[0];
            for (int i = 1; i < len; i++)
            {
                if (values[i] > m)
                    m = values[i];
            }
            return m;
        }

        // Returns /f/ raised to power /p/.
        public static float Pow(float f, float p) { return (float)Math.Pow(f, p); }

        // Returns e raised to the specified power.
        public static float Exp(float power) { return (float)Math.Exp(power); }

        // Returns the logarithm of a specified number in a specified base.
        public static float Log(float f, float p) { return (float)Math.Log(f, p); }

        // Returns the natural (base e) logarithm of a specified number.
        public static float Log(float f) { return (float)Math.Log(f); }

        // Returns the base 10 logarithm of a specified number.
        public static float Log10(float f) { return (float)Math.Log10(f); }

        // Returns the smallest integer greater to or equal to /f/.
        public static float Ceil(float f) { return (float)Math.Ceiling(f); }

        // Returns the largest integer smaller to or equal to /f/.
        public static float Floor(float f) { return (float)Math.Floor(f); }

        // Returns /f/ rounded to the nearest integer.
        public static float Round(float f) { return (float)Math.Round(f); }

        // Returns the smallest integer greater to or equal to /f/.
        public static int CeilToInt(float f) { return (int)Math.Ceiling(f); }

        // Returns the largest integer smaller to or equal to /f/.
        public static int FloorToInt(float f) { return (int)Math.Floor(f); }

        // Returns /f/ rounded to the nearest integer.
        public static int RoundToInt(float f) { return (int)Math.Round(f); }

        // Returns the sign of /f/.
        public static float Sign(float f) { return f >= 0F ? 1F : -1F; }

        // The infamous ''3.14159265358979...'' value (RO).
        public const float PI = (float)Math.PI;

        // A representation of positive infinity (RO).
        public const float Infinity = Single.PositiveInfinity;

        // A representation of negative infinity (RO).
        public const float NegativeInfinity = Single.NegativeInfinity;

        // Degrees-to-radians conversion constant (RO).
        public const float Deg2Rad = PI * 2F / 360F;

        // Radians-to-degrees conversion constant (RO).
        public const float Rad2Deg = 1F / Deg2Rad;

        // We cannot round to more decimals than 15 according to docs for System.Math.Round.
        internal const int kMaxDecimals = 15;

        // A tiny floating point value (RO).
        public static readonly float Epsilon = (float)double.Epsilon;

        // Clamps a value between a minimum float and maximum float value.
        public static float Clamp(float value, float min, float max)
        {
            if (value < min)
                value = min;
            else if (value > max)
                value = max;
            return value;
        }

        // Clamps value between min and max and returns value.
        // Set the position of the transform to be that of the time
        // but never less than 1 or more than 3
        //
        public static int Clamp(int value, int min, int max)
        {
            if (value < min)
                value = min;
            else if (value > max)
                value = max;
            return value;
        }

        // Clamps value between 0 and 1 and returns value
        public static float Clamp01(float value)
        {
            if (value < 0F)
                return 0F;
            else if (value > 1F)
                return 1F;
            else
                return value;
        }

        // Interpolates between /a/ and /b/ by /t/. /t/ is clamped between 0 and 1.
        public static float Lerp(float a, float b, float t)
        {
            return a + (b - a) * Clamp01(t);
        }

        // Interpolates between /a/ and /b/ by /t/ without clamping the interpolant.
        public static float LerpUnclamped(float a, float b, float t)
        {
            return a + (b - a) * t;
        }

        // Same as ::ref::Lerp but makes sure the values interpolate correctly when they wrap around 360 degrees.
        public static float LerpAngle(float a, float b, float t)
        {
            float delta = Repeat((b - a), 360);
            if (delta > 180)
                delta -= 360;
            return a + delta * Clamp01(t);
        }

        // Moves a value /current/ towards /target/.
        static public float MoveTowards(float current, float target, float maxDelta)
        {
            if (Mathf.Abs(target - current) <= maxDelta)
                return target;
            return current + Mathf.Sign(target - current) * maxDelta;
        }

        // Same as ::ref::MoveTowards but makes sure the values interpolate correctly when they wrap around 360 degrees.
        static public float MoveTowardsAngle(float current, float target, float maxDelta)
        {
            float deltaAngle = DeltaAngle(current, target);
            if (-maxDelta < deltaAngle && deltaAngle < maxDelta)
                return target;
            target = current + deltaAngle;
            return MoveTowards(current, target, maxDelta);
        }

        // Interpolates between /min/ and /max/ with smoothing at the limits.
        public static float SmoothStep(float from, float to, float t)
        {
            t = Mathf.Clamp01(t);
            t = -2.0F * t * t * t + 3.0F * t * t;
            return to * t + from * (1F - t);
        }

        //*undocumented
        public static float Gamma(float value, float absmax, float gamma)
        {
            bool negative = value < 0F;
            float absval = Abs(value);
            if (absval > absmax)
                return negative ? -absval : absval;

            float result = Pow(absval / absmax, gamma) * absmax;
            return negative ? -result : result;
        }

        // Compares two floating point values if they are similar.
        public static bool Approximately(float a, float b)
        {
            // If a or b is zero, compare that the other is less or equal to epsilon.
            // If neither a or b are 0, then find an epsilon that is good for
            // comparing numbers at the maximum magnitude of a and b.
            // Floating points have about 7 significant digits, so
            // 1.000001f can be represented while 1.0000001f is rounded to zero,
            // thus we could use an epsilon of 0.000001f for comparing values close to 1.
            // We multiply this epsilon by the biggest magnitude of a and b.
            return Abs(b - a) < Max(0.000001f * Max(Abs(a), Abs(b)), Epsilon * 8);
        }

       

        

        // Loops the value t, so that it is never larger than length and never smaller than 0.
        public static float Repeat(float t, float length)
        {
            return Clamp(t - Mathf.Floor(t / length) * length, 0.0f, length);
        }

        // PingPongs the value t, so that it is never larger than length and never smaller than 0.
        public static float PingPong(float t, float length)
        {
            t = Repeat(t, length * 2F);
            return length - Mathf.Abs(t - length);
        }

        // Calculates the ::ref::Lerp parameter between of two values.
        public static float InverseLerp(float a, float b, float value)
        {
            if (a != b)
                return Clamp01((value - a) / (b - a));
            else
                return 0.0f;
        }

        // Calculates the shortest difference between two given angles.
        public static float DeltaAngle(float current, float target)
        {
            float delta = Mathf.Repeat((target - current), 360.0F);
            if (delta > 180.0F)
                delta -= 360.0F;
            return delta;
        }


        static internal long RandomToLong(System.Random r)
        {
            var buffer = new byte[8];
            r.NextBytes(buffer);
            return (long)(System.BitConverter.ToUInt64(buffer, 0) & System.Int64.MaxValue);
        }

        internal static float ClampToFloat(double value)
        {
            if (double.IsPositiveInfinity(value))
                return float.PositiveInfinity;

            if (double.IsNegativeInfinity(value))
                return float.NegativeInfinity;

            if (value < float.MinValue)
                return float.MinValue;

            if (value > float.MaxValue)
                return float.MaxValue;

            return (float)value;
        }

        internal static int ClampToInt(long value)
        {
            if (value < int.MinValue)
                return int.MinValue;

            if (value > int.MaxValue)
                return int.MaxValue;

            return (int)value;
        }

        internal static float RoundToMultipleOf(float value, float roundingValue)
        {
            if (roundingValue == 0)
                return value;
            return Mathf.Round(value / roundingValue) * roundingValue;
        }

        internal static float GetClosestPowerOfTen(float positiveNumber)
        {
            if (positiveNumber <= 0)
                return 1;
            return Mathf.Pow(10, Mathf.RoundToInt(Mathf.Log10(positiveNumber)));
        }

        internal static int GetNumberOfDecimalsForMinimumDifference(float minDifference)
        {
            return Mathf.Clamp(-Mathf.FloorToInt(Mathf.Log10(Mathf.Abs(minDifference))), 0, kMaxDecimals);
        }

        internal static int GetNumberOfDecimalsForMinimumDifference(double minDifference)
        {
            return (int)System.Math.Max(0.0, -System.Math.Floor(System.Math.Log10(System.Math.Abs(minDifference))));
        }

        internal static float RoundBasedOnMinimumDifference(float valueToRound, float minDifference)
        {
            if (minDifference == 0)
                return DiscardLeastSignificantDecimal(valueToRound);
            return (float)System.Math.Round(valueToRound, GetNumberOfDecimalsForMinimumDifference(minDifference),
                System.MidpointRounding.AwayFromZero);
        }

        internal static double RoundBasedOnMinimumDifference(double valueToRound, double minDifference)
        {
            if (minDifference == 0)
                return DiscardLeastSignificantDecimal(valueToRound);
            return System.Math.Round(valueToRound, GetNumberOfDecimalsForMinimumDifference(minDifference),
                System.MidpointRounding.AwayFromZero);
        }

        internal static float DiscardLeastSignificantDecimal(float v)
        {
            int decimals = Mathf.Clamp((int)(5 - Mathf.Log10(Mathf.Abs(v))), 0, kMaxDecimals);
            return (float)System.Math.Round(v, decimals, System.MidpointRounding.AwayFromZero);
        }

        internal static double DiscardLeastSignificantDecimal(double v)
        {
            int decimals = System.Math.Max(0, (int)(5 - System.Math.Log10(System.Math.Abs(v))));
            try
            {
                return System.Math.Round(v, decimals);
            }
            catch (System.ArgumentOutOfRangeException)
            {
                // This can happen for very small numbers.
                return 0;
            }
        }
    }
}