Add ParticleSystem, fix incorrect Argb conversion in Color, remove byte casting in LerpColor, update TestGame to demostrate particle system.

Voile/Source/SceneGraph/Entities/Particles2d.cs

@@ -1,162 +0,0 @@
-using System.Drawing;
-using System.Numerics;
-using Voile.Rendering;
-
-namespace Voile.SceneGraph
-{
-    // TODO: add oneshot parameter.
-    public class Particles2d : Drawable2d
-    {
-        public int MaxParticles => _maxParticles;
-        public ParticleSettings Settings => _settings;
-
-        public Particles2d(ParticleSettings settings)
-        {
-            _settings = settings;
-            _maxParticles = _settings.MaxParticles;
-            _particleIndex = _maxParticles - 1;
-
-            _particles = new Particle[_maxParticles];
-        }
-
-        public void Restart()
-        {
-            CleanupParticles();
-
-            // Allocate a new particle array if max particles property got changed.
-            if (_maxParticles != _settings.MaxParticles)
-            {
-                _particles = new Particle[_maxParticles];
-            }
-        }
-
-        public override void OnDraw(RenderSystem renderer)
-        {
-            foreach (var particle in _particles)
-            {
-                if (!particle.Alive) continue;
-
-                var t = particle.LifeTimeRemaining / particle.LifeTime;
-                var scale = MathUtils.Lerp(_settings.ScaleEnd, _settings.ScaleBegin, t);
-                var color = MathUtils.LerpColor(_settings.ColorEnd, _settings.ColorBegin, t);
-
-                renderer.SetTransform(particle.Position, Vector2.Zero, particle.Rotation);
-                renderer.DrawRectangle(Vector2.One * scale, color);
-            }
-        }
-        protected override void OnStart()
-        {
-            base.OnStart();
-            // Emit();
-        }
-        protected override void OnUpdate(double dt)
-        {
-            base.OnUpdate(dt);
-
-            var rate = (int)MathUtils.Lerp(1, _maxParticles, _settings.Explosiveness);
-            for (int i = 0; i < rate; i++)
-            {
-                Emit();
-            }
-
-            for (int i = 0; i < _maxParticles; i++)
-            {
-                var particle = _particles[i];
-                if (!particle.Alive) continue;
-
-                if (particle.LifeTimeRemaining <= 0.0f)
-                {
-                    particle.Alive = false;
-                    continue;
-                }
-
-                particle.LifeTimeRemaining -= (float)dt;
-                particle.Velocity += _settings.Gravity * (float)dt;
-                particle.Position += particle.Velocity * (float)dt;
-                particle.Rotation += particle.AngularVelocity * (float)dt;
-
-                particle.Velocity -= particle.Velocity * _settings.Damping * (float)dt;
-
-                _particles[i] = particle;
-            }
-        }
-
-        private void Emit()
-        {
-            Particle particle = _particles[_particleIndex];
-            if (!(particle.LifeTimeRemaining <= 0)) return;
-            particle.Alive = true;
-            particle.Position = GetEmitPosition();
-            particle.Velocity = _settings.Direction * _settings.LinearVelocity;
-
-            particle.Velocity += Vector2.One * _settings.LinearVelocityRandom * ((float)_random.NextDouble() - 0.5f);
-
-            particle.AngularVelocity = _settings.AngularVelocity;
-            particle.AngularVelocity += 1f * _settings.AngularVelocityRandom * ((float)_random.NextDouble() - 0.5f);
-
-            particle.LifeTime = _settings.LifeTime;
-            particle.LifeTimeRemaining = particle.LifeTime;
-
-            _particles[_particleIndex] = particle;
-            _particleIndex = --_particleIndex <= 0 ? _maxParticles - 1 : --_particleIndex;
-        }
-
-        private void CleanupParticles() => Array.Clear(_particles);
-        private Vector2 GetEmitPosition()
-        {
-            // https://gamedev.stackexchange.com/questions/26713/calculate-random-points-pixel-within-a-circle-image
-            var angle = _random.NextDouble() * Math.PI * 2;
-            float radius = (float)Math.Sqrt(_random.NextDouble()) * _settings.EmitRadius;
-
-            float x = Position.X + radius * (float)Math.Cos(angle);
-            float y = Position.Y + radius * (float)Math.Sin(angle);
-
-            return new Vector2(x, y);
-        }
-
-        private ParticleSettings _settings;
-        private int _maxParticles;
-        private Particle[] _particles;
-        private int _particleIndex;
-
-        // TODO: replace a random function for better distribution and performance.
-        private LehmerRandom _random = new LehmerRandom();
-    }
-
-    public struct ParticleSettings
-    {
-        public ParticleSettings()
-        {
-        }
-        public float EmitRadius;
-        public float LifeTime;
-        public float Explosiveness;
-        public int MaxParticles;
-        public Vector2 Direction;
-        public float LinearVelocity;
-        public float AngularVelocity = 0.0f;
-        public float AngularVelocityRandom;
-        public float LinearVelocityRandom;
-        public Vector2 Gravity;
-        public float ScaleBegin = 16f;
-        public float ScaleEnd = 0.0f;
-        public Color ColorBegin = Color.White;
-        public Color ColorEnd = Color.Black;
-        public float Damping = 0.0f;
-    }
-
-    public struct Particle
-    {
-        public Particle()
-        {
-        }
-        public Vector2 Position;
-        public Vector2 Velocity;
-        public float AngularVelocity;
-        public float LifeTime;
-        public float LifeTimeRemaining;
-        public float Scale;
-        public float Rotation;
-        public bool Alive = true;
-    }
-}

Voile/Source/Systems/ISystem.cs

@@ -2,6 +2,9 @@ namespace Voile;
 
 public interface IStartableSystem
 {
+    /// <summary>
+    /// Starts this system.
+    /// </summary>
     void Start();
 }
 

Voile/Source/Systems/ParticleSystem.cs

@@ -0,0 +1,205 @@
+using System.Numerics;
+using Voile.Rendering;
+using Voile.Utils;
+
+namespace Voile.Systems;
+
+public struct Particle
+{
+    public Particle()
+    {
+    }
+
+    public int EmitterIndex { get; set; }
+    public int ColorArgb { get; set; }
+    public Vector2 Position { get; set; }
+    public Vector2 Velocity { get; set; }
+    public float AngularVelocity { get; set; }
+    public float LifeTime { get; set; } = 1.0f;
+    public float LifeTimeRemaining { get; set; }
+    public float Scale { get; set; }
+    public float Rotation { get; set; }
+    public bool Alive { get; set; } = true;
+}
+
+public class ParticleEmitterSettings
+{
+    public int MaxParticles { get; set; } = 16;
+    public float EmitRadius { get; set; }
+    public float LifeTime { get; set; } = 1.0f;
+    public float Explosiveness { get; set; }
+    public Vector2 Direction { get; set; } = -Vector2.UnitY;
+    public float LinearVelocity { get; set; } = 980.0f;
+    public float AngularVelocity { get; set; }
+    public float AngularVelocityRandom { get; set; }
+    public float LinearVelocityRandom { get; set; } = 0.5f;
+    public Vector2 Gravity { get; set; } = Vector2.UnitY * 980f;
+    public float ScaleBegin { get; set; } = 1.0f;
+    public float ScaleEnd { get; set; } = 0.0f;
+    public Color ColorBegin { get; set; } = Color.White;
+    public Color ColorEnd { get; set; } = Color.Black;
+    public float Damping { get; set; } = 1.0f;
+}
+
+public class ParticleEmitter : IUpdatableSystem
+{
+    public ReadOnlySpan<Particle> Particles => _particles.AsSpan();
+    public Vector2 OriginPosition => _originPosition;
+    public ParticleEmitterSettings Settings => _settings;
+
+    public ParticleEmitter(Vector2 originPosition, ParticleEmitterSettings settings, ArraySegment<Particle> particles)
+    {
+        _originPosition = originPosition;
+
+        _settings = settings;
+        _maxParticles = _settings.MaxParticles;
+        _particleIndex = _maxParticles - 1;
+
+        _particles = particles;
+
+        _random = new LehmerRandom();
+    }
+
+    public void Update(double deltaTime)
+    {
+        var rate = (int)MathUtils.Lerp(1, _maxParticles, _settings.Explosiveness);
+        for (int i = 0; i < rate; i++)
+        {
+            Emit();
+        }
+
+        for (int i = 0; i < _maxParticles; i++)
+        {
+            var particle = _particles[i];
+            if (!particle.Alive) continue;
+
+            if (particle.LifeTimeRemaining <= 0.0f)
+            {
+                particle.Alive = false;
+                continue;
+            }
+
+            particle.LifeTimeRemaining = Math.Clamp(particle.LifeTimeRemaining - (float)deltaTime, 0.0f, particle.LifeTime);
+
+            var t = particle.LifeTimeRemaining / particle.LifeTime;
+
+            particle.Velocity += _settings.Gravity * (float)deltaTime;
+            particle.Position += particle.Velocity * (float)deltaTime;
+            particle.Rotation += particle.AngularVelocity * (float)deltaTime;
+            particle.Scale = MathUtils.Lerp(Settings.ScaleEnd, Settings.ScaleBegin, t);
+
+            var color = MathUtils.LerpColor(Settings.ColorEnd, Settings.ColorBegin, t);
+            particle.ColorArgb = color.Argb;
+
+            particle.Velocity -= particle.Velocity * _settings.Damping * (float)deltaTime;
+
+            _particles[i] = particle;
+        }
+    }
+
+    private void Emit()
+    {
+        Particle particle = _particles[_particleIndex];
+        if (!(particle.LifeTimeRemaining <= 0)) return;
+        particle.Alive = true;
+        particle.Position = GetEmitPosition();
+        particle.Velocity = _settings.Direction * _settings.LinearVelocity;
+
+        particle.Velocity += Vector2.One * _settings.LinearVelocityRandom * ((float)_random.NextDouble() - 0.5f);
+
+        particle.AngularVelocity = _settings.AngularVelocity;
+        particle.AngularVelocity += 1f * _settings.AngularVelocityRandom * ((float)_random.NextDouble() - 0.5f);
+
+        particle.LifeTime = _settings.LifeTime;
+        particle.LifeTimeRemaining = particle.LifeTime;
+
+        _particles[_particleIndex] = particle;
+        _particleIndex = --_particleIndex <= 0 ? _maxParticles - 1 : --_particleIndex;
+    }
+
+    private Vector2 GetEmitPosition()
+    {
+        // https://gamedev.stackexchange.com/questions/26713/calculate-random-points-pixel-within-a-circle-image
+        var angle = _random.NextDouble() * Math.PI * 2;
+        float radius = (float)Math.Sqrt(_random.NextDouble()) * _settings.EmitRadius;
+
+        float x = radius * (float)Math.Cos(angle);
+        float y = radius * (float)Math.Sin(angle);
+
+        return new Vector2(x, y);
+    }
+
+    private LehmerRandom _random;
+    private int _maxParticles;
+    private int _particleIndex;
+    private Vector2 _originPosition = Vector2.Zero;
+    private ArraySegment<Particle> _particles;
+    private ParticleEmitterSettings _settings;
+}
+
+public class ParticleSystem : IUpdatableSystem, IDisposable
+{
+    /// <summary>
+    /// Maximum amount of particles emittable by the system.
+    /// </summary>
+    public int ParticleLimit { get; set; } = 8192;
+
+    public IReadOnlyList<ParticleEmitter> Emitters => _emitters;
+
+    public ParticleSystem()
+    {
+        _particleIndex = ParticleLimit - 1;
+        _particles = new Particle[ParticleLimit];
+    }
+
+    public void CreateEmitter(Vector2 originPosition, ParticleEmitterSettings settings)
+    {
+        if (_emitterSliceOffset + settings.MaxParticles >= ParticleLimit - 1)
+        {
+            _logger.Error("Cannot create an emitter! Reached particle limit.");
+            return;
+        }
+
+        var particles = new ArraySegment<Particle>(_particles, _emitterSliceOffset, settings.MaxParticles);
+
+        // foreach (var particle in particles)
+        // {
+        //     particle.LifeTime = settings.LifeTime;
+        // }
+
+        for (int i = 0; i < particles.Count; i++)
+        {
+            var particle = particles[i];
+            particle.LifeTime = settings.LifeTime;
+        }
+
+        var emitter = new ParticleEmitter(originPosition, settings, particles);
+
+        _emitters.Add(emitter);
+
+        _emitterSliceOffset += settings.MaxParticles;
+    }
+
+    public void Update(double deltaTime)
+    {
+        foreach (var emitter in _emitters)
+        {
+            emitter.Update(deltaTime);
+        }
+    }
+
+    public void Dispose()
+    {
+        CleanupParticles();
+    }
+
+    private void CleanupParticles() => Array.Clear(_particles);
+    private Particle[] _particles;
+    private int _particleIndex;
+
+    private int _emitterSliceOffset;
+
+    private List<ParticleEmitter> _emitters = new();
+
+    private Logger _logger = new(nameof(ParticleSystem));
+}

Voile/Source/Utils/Color.cs

@@ -37,21 +37,18 @@ namespace Voile
         public float R { get; set; }
         public float G { get; set; }
         public float B { get; set; }
-        public float A { get; set; }
+        public float A { get; set; } = 1.0f;
 
         public int Argb
         {
             get
             {
-                int c = (ushort)Math.Round(A * 255f);
-                c <<= 8;
-                c |= (ushort)Math.Round(R * 255f);
-                c <<= 8;
-                c |= (ushort)Math.Round(G * 255f);
-                c <<= 8;
-                c |= (ushort)Math.Round(B * 255f);
+                int a = (int)Math.Round(A * 255f) << 24;
+                int r = (int)Math.Round(R * 255f) << 16;
+                int g = (int)Math.Round(G * 255f) << 8;
+                int b = (int)Math.Round(B * 255f);
 
-                return c;
+                return a | r | g | b;
             }
         }
 

Voile/Source/Utils/MathUtils.cs

@@ -8,10 +8,10 @@ namespace Voile
 
         public static Color LerpColor(Color colorA, Color colorB, double t)
         {
-            var r = (byte)Lerp(colorA.R, colorB.R, t);
-            var g = (byte)Lerp(colorA.G, colorB.G, t);
-            var b = (byte)Lerp(colorA.B, colorB.B, t);
-            var a = (byte)Lerp(colorA.A, colorB.A, t);
+            var r = Lerp(colorA.R, colorB.R, t);
+            var g = Lerp(colorA.G, colorB.G, t);
+            var b = Lerp(colorA.B, colorB.B, t);
+            var a = Lerp(colorA.A, colorB.A, t);
 
             return new Color(r, g, b, a);
         }