diff --git a/CHANGELOG.md b/CHANGELOG.md index 9fc730b..32229ec 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 - Added .NET 7 target. - X10D: Added `IntrinsicExtensions` and `IntrinsicUtility` which offer methods for vectors in `System.Runtime.Instrinsics`. (#70) - X10D: Added `MathUtility.Bias(float, float)` and `MathUtility.Bias(double, double)`. +- X10D: Added `MathUtility.ExponentialDecay(float, float, float)` and `MathUtility.ExponentialDecay(double, double, double)`. - X10D: Added `MathUtility.InverseLerp(float, float, float)` and `MathUtility.InverseLerp(double, double, double)` - X10D: Added `MathUtility.ScaleRange(float, float, float, float, float)` and `MathUtility.ScaleRange(double, double, double, double, double)` diff --git a/X10D.Tests/src/Math/MathUtilityTests.cs b/X10D.Tests/src/Math/MathUtilityTests.cs index b230986..2834643 100644 --- a/X10D.Tests/src/Math/MathUtilityTests.cs +++ b/X10D.Tests/src/Math/MathUtilityTests.cs @@ -39,6 +39,32 @@ public class MathUtilityTests Assert.AreEqual(0.8f, floatResult, 1e-4f); } + [TestMethod] + public void ExponentialDecay_ShouldReturnCorrectValue_GivenDouble() + { + const double value = 100.0; + const double alpha = 0.5; + const double decay = 0.1; + + const double expected = 95.122942; + double actual = MathUtility.ExponentialDecay(value, alpha, decay); + + Assert.AreEqual(expected, actual, 1e-6); + } + + [TestMethod] + public void ExponentialDecay_ShouldReturnCorrectValue_GivenSingle() + { + const float value = 100.0f; + const float alpha = 0.5f; + const float decay = 0.1f; + + const float expected = 95.12295f; + float actual = MathUtility.ExponentialDecay(value, alpha, decay); + + Assert.AreEqual(expected, actual, 1e-6f); + } + [TestMethod] public void GammaToLinear_ShouldReturnQuarter_GivenQuarterAndGamma1() { diff --git a/X10D/src/Math/MathUtility.cs b/X10D/src/Math/MathUtility.cs index d76b03a..a3549a0 100644 --- a/X10D/src/Math/MathUtility.cs +++ b/X10D/src/Math/MathUtility.cs @@ -39,6 +39,30 @@ public static class MathUtility return value / ((1.0 / bias - 2.0) * (1.0 - value) + 1.0); } + /// + /// Calculates exponential decay for a value. + /// + /// The value to decay. + /// A factor by which to scale the decay. + /// The decay amount. + /// The exponentially decayed value. + public static float ExponentialDecay(float value, float alpha, float decay) + { + return value * MathF.Exp(-decay * alpha); + } + + /// + /// Calculates exponential decay for a value. + /// + /// The value to decay. + /// A factor by which to scale the decay. + /// The decay amount. + /// The exponentially decayed value. + public static double ExponentialDecay(double value, double alpha, double decay) + { + return value * System.Math.Exp(-decay * alpha); + } + /// /// Converts a gamma-encoded value to a linear value using a gamma value of 2.2. ///