refactor: moved drawable triangles into systems project for platform agnosticism

Engine.Core/Abstract/ICamera.cs

@@ -0,0 +1,17 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Represents a camera with view and projections matrices in the engine.
+/// </summary>
+public interface ICamera
+{
+    /// <summary>
+    /// View <see cref="Matrix4x4"/> of the <see cref="ICamera"/>.
+    /// </summary>
+    Matrix4x4 ViewMatrix { get; }
+
+    /// <summary>
+    /// Projection <see cref="Matrix4x4"/> of the <see cref="ICamera"/>.
+    /// </summary>
+    Matrix4x4 ProjectionMatrix { get; }
+}

Engine.Core/Abstract/ICamera2D.cs

@@ -3,7 +3,7 @@ namespace Engine.Core;
 /// <summary>
 /// Represents a 2D camera in the engine.
 /// </summary>
-public interface ICamera2D : IBehaviour2D
+public interface ICamera2D : ICamera, IBehaviour2D
 {
     /// <summary>
     /// The zoom level of the camera.

Engine.Core/Abstract/ICamera3D.cs

@@ -3,7 +3,7 @@ namespace Engine.Core;
 /// <summary>
 /// Represents a 3D camera in the engine.
 /// </summary>
-public interface ICamera3D : IBehaviour3D
+public interface ICamera3D : ICamera, IBehaviour3D
 {
     /// <summary>
     /// Event triggered when the near plane of the <see cref="ICamera3D"/> changes.

Engine.Core/Primitives/Matrix4x4.cs

@@ -62,6 +62,11 @@ public readonly struct Matrix4x4(
         0f, 0f, 0f, 1f
     );
 
+    /// <summary>
+    /// Represents the inverted version of this <see cref="Matrix4x4"/>.
+    /// </summary>
+    public Matrix4x4 Inverse => Invert(this);
+
     public static Matrix4x4 operator *(Matrix4x4 a, Matrix4x4 b) => new(
         a.M11 * b.M11 + a.M12 * b.M21 + a.M13 * b.M31 + a.M14 * b.M41,
         a.M11 * b.M12 + a.M12 * b.M22 + a.M13 * b.M32 + a.M14 * b.M42,
@@ -129,6 +134,74 @@ public readonly struct Matrix4x4(
          m.M13 * m.M21 * m.M32 * m.M44 - m.M11 * m.M23 * m.M32 * m.M44 -
          m.M12 * m.M21 * m.M33 * m.M44 + m.M11 * m.M22 * m.M33 * m.M44;
 
+    /// <summary>
+    /// Inverts the given <see cref="Matrix4x4"/>.
+    /// </summary>
+    /// <param name="m">The <see cref="Matrix4x4"/>.</param>
+    /// <returns>The inverted <see cref="Matrix4x4"/> of the given <see cref="Matrix4x4"/>.</returns>
+    public static Matrix4x4 Invert(Matrix4x4 m)
+    {
+        float m1 = m.M11, m2 = m.M12, m3 = m.M13, m4 = m.M14;
+        float m5 = m.M21, m6 = m.M22, m7 = m.M23, m8 = m.M24;
+        float m9 = m.M31, m10 = m.M32, m11 = m.M33, m12 = m.M34;
+        float m13 = m.M41, m14 = m.M42, m15 = m.M43, m16 = m.M44;
+
+        float num = m11 * m16 - m12 * m15;
+        float num2 = m10 * m16 - m12 * m14;
+        float num3 = m10 * m15 - m11 * m14;
+        float num4 = m9 * m16 - m12 * m13;
+        float num5 = m9 * m15 - m11 * m13;
+        float num6 = m9 * m14 - m10 * m13;
+
+        float num7 = m6 * num - m7 * num2 + m8 * num3;
+        float num8 = -(m5 * num - m7 * num4 + m8 * num5);
+        float num9 = m5 * num2 - m6 * num4 + m8 * num6;
+        float num10 = -(m5 * num3 - m6 * num5 + m7 * num6);
+
+        float invDet = 1f / (m1 * num7 + m2 * num8 + m3 * num9 + m4 * num10);
+
+        float r11 = num7 * invDet;
+        float r21 = num8 * invDet;
+        float r31 = num9 * invDet;
+        float r41 = num10 * invDet;
+
+        float r12 = (-(m2 * num - m3 * num2 + m4 * num3)) * invDet;
+        float r22 = (m1 * num - m3 * num4 + m4 * num5) * invDet;
+        float r32 = (-(m1 * num2 - m2 * num4 + m4 * num6)) * invDet;
+        float r42 = (m1 * num3 - m2 * num5 + m3 * num6) * invDet;
+
+        float num12 = m7 * m16 - m8 * m15;
+        float num13 = m6 * m16 - m8 * m14;
+        float num14 = m6 * m15 - m7 * m14;
+        float num15 = m5 * m16 - m8 * m13;
+        float num16 = m5 * m15 - m7 * m13;
+        float num17 = m5 * m14 - m6 * m13;
+
+        float r13 = (m2 * num12 - m3 * num13 + m4 * num14) * invDet;
+        float r23 = (-(m1 * num12 - m3 * num15 + m4 * num16)) * invDet;
+        float r33 = (m1 * num13 - m2 * num15 + m4 * num17) * invDet;
+        float r43 = (-(m1 * num14 - m2 * num16 + m3 * num17)) * invDet;
+
+        float num18 = m7 * m12 - m8 * m11;
+        float num19 = m6 * m12 - m8 * m10;
+        float num20 = m6 * m11 - m7 * m10;
+        float num21 = m5 * m12 - m8 * m9;
+        float num22 = m5 * m11 - m7 * m9;
+        float num23 = m5 * m10 - m6 * m9;
+
+        float r14 = (-(m2 * num18 - m3 * num19 + m4 * num20)) * invDet;
+        float r24 = (m1 * num18 - m3 * num21 + m4 * num22) * invDet;
+        float r34 = (-(m1 * num19 - m2 * num21 + m4 * num23)) * invDet;
+        float r44 = (m1 * num20 - m2 * num22 + m3 * num23) * invDet;
+
+        return new(
+            r11, r12, r13, r14,
+            r21, r22, r23, r24,
+            r31, r32, r33, r34,
+            r41, r42, r43, r44
+        );
+    }
+
     public static Matrix4x4 CreateTranslation(Vector3D position) => new(
         1f, 0f, 0f, 0f,
         0f, 1f, 0f, 0f,
@@ -136,6 +209,13 @@ public readonly struct Matrix4x4(
         position.X, position.Y, position.Z, 1
     );
 
+    public static Matrix4x4 CreateScale(float scale) => new(
+        scale, 0f, 0f, 0f,
+        0f, scale, 0f, 0f,
+        0f, 0f, scale, 0f,
+        0f, 0f, 0f, 1f
+    );
+
     public static Matrix4x4 CreateScale(Vector3D scale) => new(
         scale.X, 0f, 0f, 0f,
         0f, scale.Y, 0f, 0f,
@@ -261,12 +341,18 @@ public static class Matrix4x4Extensions
     /// <inheritdoc cref="Matrix4x4.Determinant(Matrix4x4)" />
     public static float Determinant(this Matrix4x4 matrix) => Matrix4x4.Determinant(matrix);
 
+    /// <inheritdoc cref="Matrix4x4.Invert(Matrix4x4)" />
+    public static Matrix4x4 Invert(this Matrix4x4 matrix) => Matrix4x4.Invert(matrix);
+
     /// <inheritdoc cref="Matrix4x4.CreateTranslation(Vector3D)" />
     public static Matrix4x4 ApplyTranslation(this Matrix4x4 matrix, Vector3D translation) => matrix * Matrix4x4.CreateTranslation(translation);
 
     /// <inheritdoc cref="Matrix4x4.CreateScale(Vector3D)" />
     public static Matrix4x4 ApplyScale(this Matrix4x4 matrix, Vector3 scale) => matrix * Matrix4x4.CreateScale(scale);
 
+    /// <inheritdoc cref="Matrix4x4.CreateScale(float)" />
+    public static Matrix4x4 ApplyScale(this Matrix4x4 matrix, float scale) => matrix * Matrix4x4.CreateScale(scale);
+
     /// <inheritdoc cref="Matrix4x4.CreateRotationZ(float)" />
     public static Matrix4x4 ApplyRotationX(this Matrix4x4 matrix, float radians) => matrix * Matrix4x4.CreateRotationX(radians);
 

Engine.Core/Systems/UniverseEntranceManager.cs

@@ -9,65 +9,56 @@ public class UniverseEntranceManager : Internal.BehaviourIndependent
     private static System.Func<IBehaviour, int> GetPriority() => (b) => b.Priority;
 
     private readonly ActiveBehaviourCollectorOrdered<int, IEnterUniverse> enterUniverses = new(GetPriority(), SortByAscendingPriority());
+    private readonly ActiveBehaviourCollectorOrdered<int, IExitUniverse> exitUniverses = new(GetPriority(), SortByAscendingPriority());
 
-    private readonly List<IEnterUniverse> toCallEnterUniverses = new(32);
-    private readonly List<IExitUniverse> toCallExitUniverses = new(32);
+    private bool isInitialCollectionDone = false;
+    private readonly FastListOrdered<int, IEnterUniverse> toCallEnterUniverses = new(GetPriority(), SortByAscendingPriority());
 
     protected override void OnEnteredUniverse(IUniverse universe)
     {
-        // FIXME: This causes an issue when the UniverseEntranceManager is already attached to a UniverseObject then registered into a Universe,
-        // the enter/exit universe collectors call OnUniverseObjectRegistered internally on Assign, but since the Universe calls the OnUniverseObjectRegistered
-        // event it tries to call OnUniverseObjectRegistered again on the same object, causing a duplicate entry error.
-        Debug.Assert.AssertTrue(BehaviourController.Count == 1, $"{nameof(UniverseEntranceManager)} must be in it's own {nameof(IUniverseObject)} with no other {nameof(IBehaviour)}s attached at the moment. Failing to do so might cause instantiation or serialization issues.");
+        exitUniverses.Assign(universe);
+
+        // FIXME: the isInitialCollectionDone is for the sole reason of some behaviours 
+        // adding more behaviours during entrance calls and the internal workings of 
+        // behaviour collector not being able to tell which behaviour was already called 
+        // (because it just runs a for loop with the behaviour count, and priority ordering doesn't help as well) 
+        // so it sometimes double processes or misses behaviours. A more elegant way of 
+        // handling this would be nice but for now it works good enough.
+        //
+        // SIDE NOTE: This same issue has the potential to occur on exitUniverses as well, but I've yet to run 
+        // into an instance of it actually happening so... I'm not gonna touch it until the edge case happens.  
+        isInitialCollectionDone = false;
         enterUniverses.Assign(universe);
+        isInitialCollectionDone = true;
 
-        foreach (IUniverseObject universeObject in universe)
-            OnUniverseObjectRegistered(universe, new(universeObject));
-
-        universe.OnUniverseObjectRegistered.AddListener(OnUniverseObjectRegistered);
-        universe.OnUniverseObjectUnRegistered.AddListener(OnUniverseObjectUnRegistered);
+        for (int i = toCallEnterUniverses.Count - 1; i >= 0; i--)
+            toCallEnterUniverses[i].EnterUniverse(universe);
+        toCallEnterUniverses.Clear();
     }
 
     protected override void OnExitedUniverse(IUniverse universe)
     {
         enterUniverses.Unassign();
-
-        foreach (IUniverseObject universeObject in universe)
-            OnUniverseObjectUnRegistered(universe, new(universeObject));
-
-        universe.OnUniverseObjectRegistered.RemoveListener(OnUniverseObjectRegistered);
-        universe.OnUniverseObjectUnRegistered.RemoveListener(OnUniverseObjectUnRegistered);
-    }
-
-    private void OnUniverseObjectUnRegistered(IUniverse sender, IUniverse.UniverseObjectUnRegisteredArguments args)
-    {
-        args.UniverseObjectUnregistered.BehaviourController.GetBehavioursInChildren(toCallExitUniverses);
-
-        for (int i = toCallExitUniverses.Count - 1; i >= 0; i--)
-        {
-            IExitUniverse exitUniverse = toCallExitUniverses[i];
-            toCallExitUniverses.RemoveAt(i);
-            exitUniverse.ExitUniverse(Universe);
-        }
-    }
-
-    private void OnUniverseObjectRegistered(IUniverse sender, IUniverse.UniverseObjectRegisteredArguments args)
-    {
-        for (int i = toCallEnterUniverses.Count - 1; i >= 0; i--)
-        {
-            IEnterUniverse enterUniverse = toCallEnterUniverses[i];
-            toCallEnterUniverses.RemoveAt(i);
-            enterUniverse.EnterUniverse(Universe);
-        }
+        exitUniverses.Unassign();
     }
 
     private void OnEnterUniverseCollected(IBehaviourCollector<IEnterUniverse> sender, IBehaviourCollector<IEnterUniverse>.BehaviourCollectedArguments args)
+    {
+        if (!isInitialCollectionDone)
         {
             toCallEnterUniverses.Add(args.BehaviourCollected);
+            return;
         }
 
+        args.BehaviourCollected.EnterUniverse(Universe);
+    }
+
+    private void OnExitUniverseRemoved(IBehaviourCollector<IExitUniverse> sender, IBehaviourCollector<IExitUniverse>.BehaviourRemovedArguments args)
+        => args.BehaviourRemoved.ExitUniverse(Universe);
+
     public UniverseEntranceManager()
     {
         enterUniverses.OnCollected.AddListener(OnEnterUniverseCollected);
+        exitUniverses.OnRemoved.AddListener(OnExitUniverseRemoved);
     }
 }

Engine.Integration/Engine.Integration.MonoGame/Abstract/ITriangleBatch.cs

@@ -1,12 +0,0 @@
-using Microsoft.Xna.Framework;
-
-using Engine.Core;
-
-namespace Engine.Integration.MonoGame;
-
-public interface ITriangleBatch
-{
-    void Begin(Matrix? view = null, Matrix? projection = null);
-    void Draw(Triangle triangle, ColorRGBA colorRGBA);
-    void End();
-}

Engine.Integration/Engine.Integration.MonoGame/Behaviours/MonoGameCamera2D.cs

@@ -7,31 +7,39 @@ namespace Engine.Integration.MonoGame;
 
 public class MonoGameCamera2D : Behaviour, ICamera2D, IFirstFrameUpdate, ILastFrameUpdate, IPreDraw
 {
-    public Event<MonoGameCamera2D> OnMatrixTransformChanged { get; } = new();
+    public Event<MonoGameCamera2D> OnViewMatrixChanged { get; } = new();
+    public Event<MonoGameCamera2D> OnProjectionMatrixChanged { get; } = new();
     public Event<MonoGameCamera2D> OnViewportChanged { get; } = new();
     public Event<MonoGameCamera2D> OnZoomChanged { get; } = new();
 
     public GraphicsDeviceManager Graphics { get; private set; } = null!;
     public ITransform2D Transform { get; private set; } = null!;
 
-    public Matrix MatrixTransform
+    public Matrix4x4 ProjectionMatrix
     {
         get;
-        set
+        private set
         {
             if (field == value)
                 return;
 
             field = value;
-            OnMatrixTransformChanged.Invoke(this);
+            OnProjectionMatrixChanged.Invoke(this);
         }
-    } = Matrix.Identity;
+    } = Matrix4x4.Identity;
 
-    public Vector2D Position
+    public Matrix4x4 ViewMatrix
     {
-        get => Transform.Position;
-        set => Transform.Position = value;
+        get;
+        private set
+        {
+            if (field == value)
+                return;
+
+            field = value;
+            OnViewMatrixChanged.Invoke(this);
         }
+    } = Matrix4x4.Identity;
 
     public Viewport Viewport
     {
@@ -61,21 +69,15 @@ public class MonoGameCamera2D : Behaviour, ICamera2D, IFirstFrameUpdate, ILastFr
         }
     } = 1f;
 
-    public float Rotation
-    {
-        get => Transform.Rotation;
-        set => Transform.Rotation = value;
-    }
-
     // TODO This causes delay since OnPreDraw calls assuming this is called in in Update 
     public Vector2D ScreenToWorldPosition(Vector2D screenPosition)
     {
-        Vector2D worldPosition = Vector2.Transform(screenPosition.ToVector2(), Matrix.Invert(MatrixTransform)).ToVector2D();
+        Vector2D worldPosition = Vector2.Transform(screenPosition.ToVector2(), ViewMatrix.Inverse.ToXnaMatrix()).ToVector2D();
         return worldPosition.Scale(EngineConverterExtensions.screenScale);
     }
     public Vector2D WorldToScreenPosition(Vector2D worldPosition)
     {
-        Vector2D screenPosition = Vector2.Transform(worldPosition.ToVector2(), MatrixTransform).ToVector2D();
+        Vector2D screenPosition = Vector2.Transform(worldPosition.ToVector2(), ViewMatrix.ToXnaMatrix()).ToVector2D();
         return screenPosition.Scale(EngineConverterExtensions.screenScale);
     }
 
@@ -89,11 +91,12 @@ public class MonoGameCamera2D : Behaviour, ICamera2D, IFirstFrameUpdate, ILastFr
 
     public void PreDraw()
     {
-        MatrixTransform =
-            Matrix.CreateTranslation(new Vector3(-Position.X, Position.Y, 0f)) *
-            Matrix.CreateRotationZ(Rotation * Math.DegreeToRadian) *
-            Matrix.CreateScale(Transform.Scale.X.Max(Transform.Scale.Y)) *
-            Matrix.CreateScale(Zoom) *
-            Matrix.CreateTranslation(new Vector3(Viewport.Width * .5f, Viewport.Height * .5f, 0f));
+        ProjectionMatrix = Matrix.CreateOrthographicOffCenter(Viewport.X, Viewport.Width, Viewport.Height, Viewport.Y, 0, 1).FromXnaMatrix();
+        ViewMatrix =
+            Matrix4x4.CreateTranslation(new Vector3D(-Transform.Position.X, Transform.Position.Y, 0f)) *
+            Matrix4x4.CreateRotationZ(Transform.Rotation * Math.DegreeToRadian) *
+            Matrix4x4.CreateScale(Transform.Scale.X.Max(Transform.Scale.Y)) *
+            Matrix4x4.CreateScale(Zoom) *
+            Matrix4x4.CreateTranslation(new Vector3D(Viewport.Width * .5f, Viewport.Height * .5f, 0f));
     }
 }

Engine.Integration/Engine.Integration.MonoGame/Behaviours/MonoGameCamera3D.cs

@@ -21,7 +21,7 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
     public GraphicsDeviceManager Graphics { get; private set; } = null!;
     public ITransform3D Transform { get; private set; } = null!;
 
-    public Matrix View
+    public Matrix4x4 ViewMatrix
     {
         get;
         set
@@ -29,13 +29,13 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
             if (field == value)
                 return;
 
-            Matrix previousView = field;
+            Matrix4x4 previousView = field;
             field = value;
             OnViewChanged.Invoke(this, new(previousView));
         }
-    } = Matrix.Identity;
+    } = Matrix4x4.Identity;
 
-    public Matrix Projection
+    public Matrix4x4 ProjectionMatrix
     {
         get;
         set
@@ -43,11 +43,11 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
             if (field == value)
                 return;
 
-            Matrix previousProjection = field;
+            Matrix4x4 previousProjection = field;
             field = value;
             OnProjectionChanged.Invoke(this, new(previousProjection));
         }
-    } = Matrix.Identity;
+    } = Matrix4x4.Identity;
 
     public Viewport Viewport
     {
@@ -111,14 +111,17 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
         Vector3 nearPoint = new(screenPosition.X, screenPosition.Y, 0f);
         Vector3 farPoint = new(screenPosition.X, screenPosition.Y, 1f);
 
-        Vector3 worldNear = Viewport.Unproject(nearPoint, Projection, View, Matrix.Identity);
-        Vector3 worldFar = Viewport.Unproject(farPoint, Projection, View, Matrix.Identity);
+        Matrix projection = ProjectionMatrix.ToXnaMatrix();
+        Matrix view = ViewMatrix.ToXnaMatrix();
+
+        Vector3 worldNear = Viewport.Unproject(nearPoint, projection, view, Matrix.Identity);
+        Vector3 worldFar = Viewport.Unproject(farPoint, projection, view, Matrix.Identity);
 
         Vector3 direction = Vector3.Normalize(worldFar - worldNear);
         return new(worldNear.ToVector3D(), direction.ToVector3D());
     }
 
-    public Vector2D WorldToScreenPosition(Vector3D worldPosition) => Viewport.Project(worldPosition.ToVector3(), Projection, View, Matrix.Identity).ToVector3D();
+    public Vector2D WorldToScreenPosition(Vector3D worldPosition) => Viewport.Project(worldPosition.ToVector3(), ProjectionMatrix.ToXnaMatrix(), ViewMatrix.ToXnaMatrix(), Matrix.Identity).ToVector3D();
 
     public void LastActiveFrame() => Transform.OnTransformUpdated.RemoveListener(SetDirtyOnTransformUpdate);
     public void FirstActiveFrame()
@@ -150,7 +153,7 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
         Vector3 right = Vector3.Normalize(Transform.Right.ToVector3());
         Vector3 position = Transform.Position.ToVector3();
 
-        View = new Matrix(
+        ViewMatrix = new Matrix4x4(
             right.X, up.X, forward.X, 0,
             right.Y, up.Y, forward.Y, 0,
             right.Z, up.Z, forward.Z, 0,
@@ -166,7 +169,7 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
         float yScale = 1f / (float)Math.Tan(fieldOfView / 2f);
         float xScale = yScale / Viewport.AspectRatio;
 
-        Projection = new Matrix(
+        ProjectionMatrix = new Matrix4x4(
             xScale, 0, 0, 0,
             0, yScale, 0, 0,
             0, 0, FarPlane / (FarPlane - NearPlane), 1,
@@ -174,7 +177,7 @@ public class MonoGameCamera3D : Behaviour, ICamera3D, IFirstFrameUpdate, ILastFr
         );
     }
 
-    public readonly record struct ViewChangedArguments(Matrix PreviousView);
-    public readonly record struct ProjectionChangedArguments(Matrix PreviousProjection);
+    public readonly record struct ViewChangedArguments(Matrix4x4 PreviousView);
+    public readonly record struct ProjectionChangedArguments(Matrix4x4 PreviousProjection);
     public readonly record struct ViewportChangedArguments(Viewport PreviousViewport);
 }

Engine.Integration/Engine.Integration.MonoGame/Behaviours/SpriteBatcher.cs

@@ -26,7 +26,7 @@ public class SpriteBatcher : Behaviour, IFirstFrameUpdate, IDraw
 
     public void Draw()
     {
-        spriteBatch.Begin(transformMatrix: camera2D.MatrixTransform);
+        spriteBatch.Begin(transformMatrix: camera2D.ViewMatrix.ToXnaMatrix());
         for (int i = 0; i < drawableSprites.Count; i++)
             drawableSprites[i].Draw(spriteBatch);
         spriteBatch.End();

Engine.Integration/Engine.Integration.MonoGame/Behaviours/TriangleBatcher.cs

@@ -1,40 +0,0 @@
-using System.Collections.Generic;
-
-using Microsoft.Xna.Framework;
-
-using Engine.Core;
-
-namespace Engine.Integration.MonoGame;
-
-public class TriangleBatcher : Behaviour, ITriangleBatch, IFirstFrameUpdate, IDraw
-{
-    private static Comparer<int> SortByAscendingPriority() => Comparer<int>.Create((x, y) => x.CompareTo(y));
-    private static System.Func<IBehaviour, int> GetPriority() => (b) => b.Priority;
-
-    private TriangleBatch triangleBatch = null!;
-    private MonoGameCamera2D camera2D = null!;
-
-    private readonly ActiveBehaviourCollectorOrdered<int, IDrawableTriangle> drawableShapes = new(GetPriority(), SortByAscendingPriority());
-
-    public void FirstActiveFrame()
-    {
-        MonoGameWindowContainer windowContainer = BehaviourController.UniverseObject.Universe.FindRequiredBehaviour<MonoGameWindowContainer>();
-        camera2D = BehaviourController.UniverseObject.Universe.FindRequiredBehaviour<MonoGameCamera2D>();
-
-        triangleBatch = new(windowContainer.Window.GraphicsDevice);
-        drawableShapes.Unassign();
-        drawableShapes.Assign(BehaviourController.UniverseObject.Universe);
-    }
-
-    public void Draw()
-    {
-        triangleBatch.Begin(camera2D.MatrixTransform);
-        for (int i = 0; i < drawableShapes.Count; i++)
-            drawableShapes[i].Draw(triangleBatch);
-        triangleBatch.End();
-    }
-
-    public void Begin(Matrix? view = null, Matrix? projection = null) => triangleBatch.Begin(view, projection);
-    public void Draw(Triangle triangle, ColorRGBA colorRGBA) => triangleBatch.Draw(triangle, colorRGBA);
-    public void End() => triangleBatch.End();
-}

Engine.Integration/Engine.Integration.MonoGame/EngineConverter.cs

@@ -49,6 +49,14 @@ public static class EngineConverterExtensions
         m.M41, m.M42, m.M43, m.M44
     );
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Matrix4x4 FromXnaMatrix(this Matrix m) => new(
+        m.M11, m.M12, m.M13, m.M14,
+        m.M21, m.M22, m.M23, m.M24,
+        m.M31, m.M32, m.M33, m.M34,
+        m.M41, m.M42, m.M43, m.M44
+    );
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static Microsoft.Xna.Framework.Quaternion ToXnaQuaternion(this Core.Quaternion quaternion) => new(quaternion.X, quaternion.Y, quaternion.Z, quaternion.W);
 

Engine.Integration/Engine.Integration.MonoGame/MonoGameTriangleBatch.cs

@@ -2,24 +2,26 @@ using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Graphics;
 
 using Engine.Core;
+using Engine.Systems.Graphics;
 
 namespace Engine.Integration.MonoGame;
 
-public class TriangleBatch : ITriangleBatch
+public class MonoGameTriangleBatch : Behaviour, ITriangleBatch, IFirstFrameUpdate
 {
-    private readonly GraphicsDevice graphicsDevice;
-    private readonly VertexBuffer vertexBuffer = default!;
+    private GraphicsDevice graphicsDevice = null!;
+    private VertexBuffer vertexBuffer = default!;
     private readonly VertexPositionColor[] vertices = new VertexPositionColor[1024];
 
     private int verticesIndex = 0;
     private Matrix view = Matrix.Identity;
     private Matrix projection = Matrix.Identity;
 
-    private readonly BasicEffect basicEffect = null!;
+    private BasicEffect basicEffect = null!;
     private readonly RasterizerState rasterizerState = new() { CullMode = CullMode.None };
 
-    public TriangleBatch(GraphicsDevice graphicsDevice)
+    public void FirstActiveFrame()
     {
+        GraphicsDevice graphicsDevice = Universe.FindRequiredBehaviour<MonoGameWindowContainer>().Window.GraphicsDevice;
         this.graphicsDevice = graphicsDevice;
         basicEffect = new(graphicsDevice);
         basicEffect.VertexColorEnabled = true;
@@ -41,15 +43,15 @@ public class TriangleBatch : ITriangleBatch
         vertices[verticesIndex++] = new(new(C.X, C.Y, 0f), color);
     }
 
-    public void Begin(Matrix? view = null, Matrix? projection = null)
+    public void Begin(Matrix4x4? view = null, Matrix4x4? projection = null)
     {
         if (view != null)
-            this.view = view.Value;
+            this.view = view.Value.ToXnaMatrix();
         else
             this.view = Matrix.Identity;
 
         if (projection != null)
-            this.projection = projection.Value;
+            this.projection = projection.Value.ToXnaMatrix();
         else
         {
             Viewport viewport = graphicsDevice.Viewport;

Engine.Systems/Graphics/DrawableShape2D.cs

@@ -2,9 +2,9 @@ using System.Collections.Generic;
 
 using Engine.Core;
 
-namespace Engine.Integration.MonoGame;
+namespace Engine.Systems.Graphics;
 
-public class DrawableShape : Behaviour2D, IDrawableTriangle, IPreDraw
+public class DrawableShape2D : Behaviour2D, IDrawableTriangle, IPreDraw
 {
     private readonly Shape2D shape = new([]);
     private readonly List<Triangle> worldTriangles = [];
@@ -23,7 +23,7 @@ public class DrawableShape : Behaviour2D, IDrawableTriangle, IPreDraw
 
     protected void UpdateWorldShape() => shape.Transform(Transform, worldShape);
 
-    public DrawableShape() => shape = Shape2D.Triangle;
-    public DrawableShape(Shape2D shape) => this.shape = shape;
-    public DrawableShape(Shape2D shape, ColorRGB color) { this.shape = shape; this.color = color; }
+    public DrawableShape2D() => shape = Shape2D.Triangle;
+    public DrawableShape2D(Shape2D shape) => this.shape = shape;
+    public DrawableShape2D(Shape2D shape, ColorRGB color) { this.shape = shape; this.color = color; }
 }

Engine.Systems/Graphics/IDrawableTriangle.cs

@@ -1,6 +1,6 @@
 using Engine.Core;
 
-namespace Engine.Integration.MonoGame;
+namespace Engine.Systems.Graphics;
 
 public interface IDrawableTriangle : IBehaviour
 {

Engine.Systems/Graphics/ITriangleBatch.cs

@@ -0,0 +1,10 @@
+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public interface ITriangleBatch
+{
+    void Begin(Matrix4x4? view = null, Matrix4x4? projection = null);
+    void Draw(Triangle triangle, ColorRGBA colorRGBA);
+    void End();
+}

Engine.Systems/Graphics/TriangleBatcher.cs

@@ -0,0 +1,33 @@
+using System.Collections.Generic;
+
+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public class TriangleBatcher : Behaviour, IFirstFrameUpdate, IDraw
+{
+    private static Comparer<int> SortByAscendingPriority() => Comparer<int>.Create((x, y) => x.CompareTo(y));
+    private static System.Func<IBehaviour, int> GetPriority() => (b) => b.Priority;
+
+    private ITriangleBatch triangleBatch = null!;
+    private ICamera camera = null!;
+
+    private readonly ActiveBehaviourCollectorOrdered<int, IDrawableTriangle> drawableShapes = new(GetPriority(), SortByAscendingPriority());
+
+    public void FirstActiveFrame()
+    {
+        camera = Universe.FindRequiredBehaviour<ICamera>();
+
+        triangleBatch = Universe.FindRequiredBehaviour<ITriangleBatch>();
+        drawableShapes.Unassign();
+        drawableShapes.Assign(Universe);
+    }
+
+    public void Draw()
+    {
+        triangleBatch.Begin(camera.ViewMatrix, camera.ProjectionMatrix);
+        for (int i = 0; i < drawableShapes.Count; i++)
+            drawableShapes[i].Draw(triangleBatch);
+        triangleBatch.End();
+    }
+}