feat: add MathUtility.SmoothStep (#60)

CHANGELOG.md

@@ -13,11 +13,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added new library X10D.Hosting.
 - 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)`.
+- X10D: Added `MathUtility.Bias(float, float)` and `MathUtility.Bias(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)`
 - X10D:
+- X10D: Added `MathUtility.SmoothStep(float, float, float)` and `MathUtility.SmoothStep(double, double, double)`.
   Added `Circle`, `CircleF`, `Cuboid`, `Ellipse`, `EllipseF`, `Line3D`, `Line`, `LineF`, `Polygon`, `PolygonF`, `Polyhedron`,
   and `Sphere`, to complement System.Drawing structs such as `Point` and `Rectangle`
 - X10D: Added `Color.Deconstruct()` - with optional alpha parameter.

X10D.Tests/src/Math/MathUtilityTests.cs

@@ -150,4 +150,25 @@ public class MathUtilityTests
         float result = MathUtility.ScaleRange(0.5f, 0.0f, 1.0f, 5.0f, 10.0f);
         Assert.AreEqual(7.5f, result);
     }
+
+    [TestMethod]
+    public void SmoothStep_ShouldReturnHigher_GivenAlpha1()
+    {
+        Assert.AreEqual(20.0f, MathUtility.SmoothStep(10.0f, 20.0f, 1.0f));
+        Assert.AreEqual(20.0, MathUtility.SmoothStep(10.0, 20.0, 1.0));
+    }
+
+    [TestMethod]
+    public void SmoothStep_ShouldReturnLower_GivenAlpha0()
+    {
+        Assert.AreEqual(10.0f, MathUtility.SmoothStep(10.0f, 20.0f, 0.0f));
+        Assert.AreEqual(10.0, MathUtility.SmoothStep(10.0, 20.0, 0.0));
+    }
+
+    [TestMethod]
+    public void SmoothStep_ShouldReturnMidPoint_GivenAlphaPoint5()
+    {
+        Assert.AreEqual(15.0f, MathUtility.SmoothStep(10.0f, 20.0f, 0.5f));
+        Assert.AreEqual(15.0, MathUtility.SmoothStep(10.0, 20.0, 0.5));
+    }
 }

X10D/src/Math/MathUtility.cs

@@ -308,4 +308,32 @@ public static class MathUtility
         double alpha = (value - oldMin) / oldRange;
         return (alpha * newRange) + newMin;
     }
+
+    /// <summary>
+    ///     Performs smooth Hermite interpolation from one value to a target using a specified alpha.
+    /// </summary>
+    /// <param name="value">The interpolation source.</param>
+    /// <param name="target">The interpolation target.</param>
+    /// <param name="alpha">The interpolation alpha.</param>
+    /// <returns>The interpolation result.</returns>
+    public static float SmoothStep(float value, float target, float alpha)
+    {
+        alpha = System.Math.Clamp(alpha, 0.0f, 1.0f);
+        alpha = -2.0f * alpha * alpha * alpha + 3.0f * alpha * alpha;
+        return target * alpha + value * (1.0f - alpha);
+    }
+
+    /// <summary>
+    ///     Performs smooth Hermite interpolation from one value to a target using a specified alpha.
+    /// </summary>
+    /// <param name="value">The interpolation source.</param>
+    /// <param name="target">The interpolation target.</param>
+    /// <param name="alpha">The interpolation alpha.</param>
+    /// <returns>The interpolation result.</returns>
+    public static double SmoothStep(double value, double target, double alpha)
+    {
+        alpha = System.Math.Clamp(alpha, 0.0, 1.0);
+        alpha = -2.0 * alpha * alpha * alpha + 3.0 * alpha * alpha;
+        return target * alpha + value * (1.0 - alpha);
+    }
 }