BaseGame with fixed timestep.

TODO.md

@@ -13,9 +13,9 @@
 - ~~Use GUIDs and string ID maps for fetching resources instead of string IDs alone.~~
 - Reimplement unloading.
 - Finalize ResourceManager and ResourceLoader APIs for 1.0.
+- Add async API for ResourceManager.
 - Virtual file system.
 - (stretch goal) Streamed resource loading.
-- (stretch goal) Add async API for ResourceManager.
 
 ## Serialization
 

TestGame/TestGame.cs

@@ -7,25 +7,14 @@ using System.Numerics;
 using System.Diagnostics.CodeAnalysis;
 using System.Diagnostics;
 
-public class TestGame : Game
+public class TestGame : BaseGame
 {
     public override string ResourceRoot => "Resources/";
 
-    public override void Initialize()
-    {
-        InitializeDefault();
-
-        _particleSystem = new ParticleSystem();
-
-        ResourceManager.AddResourceLoaderAssociation(new ParticleEmitterSettingsResourceLoader());
-
-        Input.AddInputMapping("reload", new InputAction[] { new KeyInputAction(KeyboardKey.R) });
-
-        _particleSimStopwatch = new Stopwatch();
-    }
-
     protected override void LoadResources()
     {
+        ResourceManager.AddResourceLoaderAssociation(new ParticleEmitterSettingsResourceLoader());
+
         if (!ResourceManager.TryLoad("fonts/Inter-Regular.ttf", out _font))
         {
 
@@ -41,12 +30,22 @@ public class TestGame : Game
 
     protected override void Ready()
     {
+        _particleSystem = new ParticleSystem();
+        Input.AddInputMapping("reload", new InputAction[] { new KeyInputAction(KeyboardKey.R) });
+        _particleSimStopwatch = new Stopwatch();
+
         _emitterId = _particleSystem.CreateEmitter(Renderer.WindowSize / 2, _fireEffect);
     }
 
-    protected override void Run()
+
+    protected override void Update(double deltaTime)
     {
-        while (Renderer.ShouldRun)
+        _particleSimStopwatch = Stopwatch.StartNew();
+        _particleSystem!.Update(deltaTime);
+        _particleSimStopwatch.Stop();
+    }
+
+    protected override void Render(double deltaTime)
     {
         if (Input.IsActionPressed("reload"))
         {
@@ -64,13 +63,6 @@ public class TestGame : Game
             _particleSystem.SetEmitterPosition(_emitterId, Input.GetMousePosition());
         }
 
-            _particleSimStopwatch = Stopwatch.StartNew();
-            _particleSystem!.Update(Renderer.FrameTime);
-            _particleSimStopwatch.Stop();
-
-            _renderStopwatch = Stopwatch.StartNew();
-
-            Renderer.BeginFrame();
         Renderer.ClearBackground(Color.Black);
         foreach (var emitter in _particleSystem!.Emitters)
         {
@@ -81,20 +73,10 @@ public class TestGame : Game
         Renderer.DrawText(_font, $"Particle Sim: {TimeSpan.FromTicks(_particleSimStopwatch.ElapsedTicks).TotalMilliseconds} ms", Color.White);
 
         Renderer.SetTransform(new Vector2(0.0f, 16.0f), Vector2.Zero);
-            Renderer.DrawText(_font, $"Render: {TimeSpan.FromTicks(_lastRenderTime).TotalMilliseconds} ms", Color.White);
+        Renderer.DrawText(_font, $"Render: {RenderFrameTime.TotalMilliseconds:F1} ms", Color.White);
 
-            Renderer.EndFrame();
-
-            _lastRenderTime = _renderStopwatch.ElapsedTicks;
-
-            _renderStopwatch.Restart();
-            _particleSimStopwatch.Restart();
-        }
-    }
-
-    public override void Shutdown()
-    {
-        ShutdownDefault();
+        Renderer.SetTransform(new Vector2(0.0f, 32.0f), Vector2.Zero);
+        Renderer.DrawText(_font, $"Update: {UpdateTimeStep * 1000:F1} ms", Color.White);
     }
 
     private void DrawEmitter(ParticleEmitter emitter)
@@ -118,8 +100,7 @@ public class TestGame : Game
 
     [NotNull] private ParticleSystem _particleSystem;
 
-    private Stopwatch _particleSimStopwatch, _renderStopwatch;
-    private long _lastRenderTime;
+    private Stopwatch _particleSimStopwatch;
     private int _emitterId;
     private ResourceRef<ParticleEmitterSettingsResource> _fireEffect;
     private ResourceRef<Font> _font;

Voile/Source/Game.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics;
 using Voile.Input;
 using Voile.Rendering;
 using Voile.Resources;
@@ -83,7 +84,6 @@ namespace Voile
             }
 
             Initialize();
-            LoadResources();
             Ready();
             Run();
             Shutdown();
@@ -116,10 +116,6 @@ namespace Voile
         /// </summary>
         public abstract void Initialize();
         /// <summary>
-        /// Called when it's time to load the game's resources, such as images or sounds.
-        /// </summary>
-        protected abstract void LoadResources();
-        /// <summary>
         /// Called when it's safe to manipulate the resources or/and systems.
         /// You can safely create game objects, scenes, etc. in this method.
         /// </summary>
@@ -143,4 +139,63 @@ namespace Voile
             Renderer.Start(RendererSettings.Default);
         }
     }
+
+    public abstract class BaseGame : Game
+    {
+        public double UpdateTimeStep { get; set; } = 1.0 / 60.0;
+        public TimeSpan UpdateFrameTime { get; private set; }
+        public TimeSpan RenderFrameTime { get; private set; }
+        public override void Initialize()
+        {
+            LoadResources();
+            InitializeDefault();
+        }
+
+        public override void Shutdown() => ShutdownDefault();
+
+        /// <summary>
+        /// Called when it's time to load the game's resources, such as images or sounds.
+        /// </summary>
+        protected abstract void LoadResources();
+
+        protected override void Run()
+        {
+            Stopwatch stopwatch = Stopwatch.StartNew();
+            double previousTime = stopwatch.Elapsed.TotalSeconds;
+
+            while (Renderer.ShouldRun)
+            {
+                double currentTime = stopwatch.Elapsed.TotalSeconds;
+                double elapsedTime = currentTime - previousTime;
+                previousTime = currentTime;
+
+                _accumulator += elapsedTime;
+
+                while (_accumulator >= UpdateTimeStep)
+                {
+                    Update(UpdateTimeStep);
+                    _accumulator -= UpdateTimeStep;
+                }
+
+                Renderer.BeginFrame();
+                Render(Renderer.FrameTime);
+                Renderer.EndFrame();
+
+                RenderFrameTime = TimeSpan.FromSeconds(Renderer.FrameTime);
+            }
+        }
+
+        /// <summary>
+        /// Triggered on each fixed timestep. Update your game's state here.
+        /// </summary>
+        /// <param name="deltaTime"></param>
+        protected abstract void Update(double deltaTime);
+        /// <summary>
+        /// Triggered when the renderer is ready to render the next frame.
+        /// </summary>
+        /// <param name="deltaTime"></param>
+        protected abstract void Render(double deltaTime);
+
+        private double _accumulator;
+    }
 }