feat: add fly-camera with view/projection matrices

VoxelEngine.Tests/CameraTests.cs

@@ -0,0 +1,43 @@
+using OpenTK.Mathematics;
+using VoxelEngine.Rendering;
+using Xunit;
+
+namespace VoxelEngine.Tests;
+
+public class CameraTests
+{
+    [Fact]
+    public void DefaultFront_PointsTowardNegativeZ()
+    {
+        var camera = new Camera(Vector3.Zero, 16f / 9f);
+
+        Assert.Equal(0f, camera.Front.X, 3);
+        Assert.Equal(0f, camera.Front.Y, 3);
+        Assert.Equal(-1f, camera.Front.Z, 3);
+    }
+
+    [Fact]
+    public void Move_TranslatesPosition()
+    {
+        var camera = new Camera(Vector3.Zero, 1f);
+        camera.Move(new Vector3(1f, 2f, 3f));
+        Assert.Equal(new Vector3(1f, 2f, 3f), camera.Position);
+    }
+
+    [Fact]
+    public void AddRotation_ClampsPitchTo89Degrees()
+    {
+        var camera = new Camera(Vector3.Zero, 1f);
+        camera.AddRotation(0f, 200f); // try to over-rotate up
+        Assert.True(camera.Pitch <= 89.0001f);
+        camera.AddRotation(0f, -400f);
+        Assert.True(camera.Pitch >= -89.0001f);
+    }
+
+    [Fact]
+    public void ProjectionMatrix_IsNotIdentity()
+    {
+        var camera = new Camera(Vector3.Zero, 1.5f);
+        Assert.NotEqual(Matrix4.Identity, camera.GetProjectionMatrix());
+    }
+}