added RcMath.Lerp()

src/DotRecast.Core/RcMath.cs

@@ -29,5 +29,11 @@ namespace DotRecast.Core
         {
             return f * f;
         }
+        
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Lerp(float value1, float value2, float amount)
+        {
+            return (value1 * (1.0f - amount)) + (value2 * amount);
+        }
     }
 }

test/DotRecast.Core.Test/RcMathTest.cs

@@ -0,0 +1,38 @@
+using System;
+using NUnit.Framework;
+
+namespace DotRecast.Core.Test;
+
+public class RcMathTest
+{
+    [Test]
+    public void TestSqr()
+    {
+        Assert.That(RcMath.Sqr(0), Is.EqualTo(0));
+        Assert.That(RcMath.Sqr(5), Is.EqualTo(25));
+        Assert.That(RcMath.Sqr(-5), Is.EqualTo(25));
+        Assert.That(RcMath.Sqr(float.PositiveInfinity), Is.EqualTo(float.PositiveInfinity));
+        Assert.That(RcMath.Sqr(float.NegativeInfinity), Is.EqualTo(float.PositiveInfinity));
+        Assert.That(RcMath.Sqr(float.NaN), Is.EqualTo(float.NaN));
+    }
+
+    [Test]
+    public void TestLerp()
+    {
+        //
+        Assert.That(RcMath.Lerp(-10, 10, 2f), Is.EqualTo(30));
+        Assert.That(RcMath.Lerp(-10, 10, 1f), Is.EqualTo(10));
+        Assert.That(RcMath.Lerp(-10, 10, 0.5f), Is.EqualTo(0));
+        Assert.That(RcMath.Lerp(-10, 10, 0.25f), Is.EqualTo(-5));
+        Assert.That(RcMath.Lerp(-10, 10, 0), Is.EqualTo(-10));
+        Assert.That(RcMath.Lerp(-10, 10, -0.5f), Is.EqualTo(-20));
+        Assert.That(RcMath.Lerp(-10, 10, -1f), Is.EqualTo(-30));
+
+        //
+        Assert.That(RcMath.Lerp(10, 10, 0.5f), Is.EqualTo(10));
+        Assert.That(RcMath.Lerp(10, 10, 0.8f), Is.EqualTo(10));
+
+        //
+        Assert.That(RcMath.Lerp(10, -10, 0.75f), Is.EqualTo(-5));
+    }
+}