feat: add seeded NoiseSource over FastNoiseLite

VoxelEngine.Tests/WorldGen/NoiseSourceTests.cs

@@ -0,0 +1,29 @@
+using VoxelEngine.World.WorldGen;
+using Xunit;
+
+namespace VoxelEngine.Tests.WorldGen;
+
+public class NoiseSourceTests
+{
+    [Fact]
+    public void SameSeed_SameCoord_IsDeterministic()
+    {
+        var a = new NoiseSource(42);
+        var b = new NoiseSource(42);
+        Assert.Equal(a.Continent(10f, 20f), b.Continent(10f, 20f));
+        Assert.Equal(a.Temperature(10f, 20f), b.Temperature(10f, 20f));
+    }
+
+    [Fact]
+    public void Output_InMinusOneToOneRange()
+    {
+        var n = new NoiseSource(7);
+        for (int i = 0; i < 200; i++)
+        {
+            float c = n.Continent(i * 3.1f, i * 1.7f);
+            float t = n.Temperature(i * 2.3f, i * 0.9f);
+            Assert.InRange(c, -1.001f, 1.001f);
+            Assert.InRange(t, -1.001f, 1.001f);
+        }
+    }
+}