New FOV algorithm that works pretty well.

Saved for posterity here, approximately:
https://twitter.com/mcmillen/status/1227326054949408768

GitOrigin-RevId: e960dad1d9241c08dbf1292c6856311d4ebd7a85

Shared/Camera.cs

@@ -5,13 +5,18 @@ using System;
 // https://gamasutra.com/blogs/ItayKeren/20150511/243083/Scroll_Back_The_Theory_and_Practice_of_Cameras_in_SideScrollers.php
 namespace SemiColinGames {
   class Camera {
-    private Rectangle bbox = new Rectangle(0, 0, 1920 / 4, 1080 / 4);
+    // Screen size in pixels is 1920x1080 divided by 4.
+    private Rectangle bbox = new Rectangle(0, 0, 480, 270);
 
     public int Width { get => bbox.Width; }
     public int Height { get => bbox.Height; }
     public int Left { get => bbox.Left; }
     public int Top { get => bbox.Top; }
 
+    public Matrix Projection {
+      get => Matrix.CreateOrthographicOffCenter(Left, Left + Width, Height, 0, -1, 1);
+    }
+
     public void Update(Point player, int worldWidth) {
       int diff = player.X - bbox.Center.X;
       if (Math.Abs(diff) > 16) {

Shared/Player.cs

@@ -11,7 +11,7 @@ namespace SemiColinGames {
       Right = 1
     };
 
-    enum Pose { Walking, Standing, Crouching, Stretching, SwordSwing, Jumping };
+    public enum Pose { Walking, Standing, Crouching, Stretching, SwordSwing, Jumping };
 
     private const int moveSpeed = 180;
     private const int jumpSpeed = -600;
@@ -46,6 +46,15 @@ namespace SemiColinGames {
       this.texture = texture;
     }
 
+    // TODO: just make Facing an int.
+    public int GetFacing {
+      get { return (int) facing; }
+    }
+
+    public Pose GetPose {
+      get { return pose; }
+    }
+
     public Point Position { get { return position; } }
 
     public void Update(float modelTime, History<Input> input, AABB[] collisionTargets) {
@@ -147,102 +156,15 @@ namespace SemiColinGames {
       } else {
         pose = Pose.Standing;
       }
-
-      DrawSightLines(collisionTargets);
     }
 
-    Vector2 Rotate(Vector2 point, float angle) {
+    public Vector2 EyePosition {
-      float cos = FMath.Cos(angle);
+      get {
-      float sin = FMath.Sin(angle);
+        bool walking = pose == Pose.Walking || pose == Pose.Jumping;
-      return new Vector2(
+        Vector2 eyeOffset = walking ? eyeOffsetWalking : eyeOffsetStanding;
-        point.X * cos - point.Y * sin,
+        return Vector2.Add(
-        point.Y * cos + point.X * sin);
+            Position.ToVector2(), new Vector2(eyeOffset.X * (int) facing, eyeOffset.Y));
-    }
-
-    bool PointInCone(
-        float visionRangeSq, float fovCos, Vector2 eyePos, Vector2 direction, Vector2 test) {
-      Vector2 delta = Vector2.Subtract(test, eyePos);
-      if (delta.LengthSquared() > visionRangeSq) {
-        return false;
       }
-      float dot = Vector2.Dot(Vector2.Normalize(direction), Vector2.Normalize(delta));
-      return dot > fovCos;
-    }
-
-    void DrawSightLines(AABB[] collisionTargets) {
-      float fov = FMath.DegToRad(45);
-      float fovCos = FMath.Cos(fov);
-      Color color = Color.LightYellow;
-
-      Vector2 eyeOffset = pose == Pose.Walking ? eyeOffsetWalking : eyeOffsetStanding;
-      Vector2 eyePos = Vector2.Add(
-        Position.ToVector2(), new Vector2(eyeOffset.X * (int) facing, eyeOffset.Y));
-
-      float visionRange = 150;
-      float visionRangeSq = visionRange * visionRange;
-      Vector2 ray = new Vector2(visionRange * (int) facing, 0);
-      if (pose == Pose.Stretching) {
-        ray = Rotate(ray, (int) facing * FMath.DegToRad(-30));
-      }
-      if (pose == Pose.Crouching) {
-        ray = Rotate(ray, (int) facing * FMath.DegToRad(30));
-      }
-      Vector2 coneBottom = Rotate(ray, fov);
-      Vector2 coneTop = Rotate(ray, -fov);
-
-      List<Vector2> points = new List<Vector2>();
-      List<AABB> boxes = new List<AABB>();
-      points.Add(Vector2.Add(eyePos, coneBottom));
-      points.Add(Vector2.Add(eyePos, coneTop));
-      foreach (AABB box in collisionTargets) {
-        int hitCount = points.Count;
-        if (PointInCone(visionRangeSq, fovCos, eyePos, ray, box.TopLeft)) {
-          points.Add(box.TopLeft);
-        }
-        if (PointInCone(visionRangeSq, fovCos, eyePos, ray, box.TopRight)) {
-          points.Add(box.TopRight);
-        }
-        if (PointInCone(visionRangeSq, fovCos, eyePos, ray, box.BottomLeft)) {
-          points.Add(box.BottomLeft);
-        }
-        if (PointInCone(visionRangeSq, fovCos, eyePos, ray, box.BottomRight)) {
-          points.Add(box.BottomRight);
-        }
-        if (points.Count > hitCount) {
-          boxes.Add(box);
-          Debug.AddRect(box, color);
-        }
-      }
-
-      HashSet<AABB> boxesSeen = new HashSet<AABB>();
-      foreach (Vector2 point in points) {
-        float minTime = 1;
-        AABB? closestBox = null;
-        Vector2 delta = Vector2.Subtract(point, eyePos);
-        foreach (AABB box in boxes) {
-          Hit? maybeHit = box.IntersectSegment(eyePos, delta);
-          if (maybeHit != null) {
-            float time = FMath.Clamp(maybeHit.Value.Time, 0, 1);
-            Vector2 target = Vector2.Add(eyePos, Vector2.Multiply(delta, time));
-            Debug.AddLine(eyePos, target, color);
-            if (time < minTime) {
-              minTime = time;
-              closestBox = box;
-            }
-          }
-        }
-        if (closestBox != null) {
-          boxesSeen.Add(closestBox.Value);
-        }
-      }
-
-      foreach (AABB box in boxesSeen) {
-        Debug.AddRect(box, Color.Orange);
-      }
-
-      Debug.AddLine(eyePos, Vector2.Add(eyePos, ray), Color.Red);
-      Debug.AddLine(eyePos, Vector2.Add(eyePos, coneTop), Color.Red);
-      Debug.AddLine(eyePos, Vector2.Add(eyePos, coneBottom), Color.Red);
     }
 
     // Returns the desired (dx, dy) for the player to move this frame.

Shared/SneakGame.cs

@@ -11,7 +11,10 @@ namespace SemiColinGames {
     const double TARGET_FRAME_TIME = 1.0 / TARGET_FPS;
 
     readonly GraphicsDeviceManager graphics;
-    RenderTarget2D renderTarget;
+    RenderTarget2D sceneTarget;
+    RenderTarget2D lightingTarget;
+
+    BasicEffect lightingEffect;
 
     SpriteBatch spriteBatch;
     SpriteFont font;
@@ -54,9 +57,22 @@ namespace SemiColinGames {
 
       Debug.Initialize(GraphicsDevice);
 
-      renderTarget = new RenderTarget2D(
+      sceneTarget = new RenderTarget2D(
         GraphicsDevice, camera.Width, camera.Height, false /* mipmap */,
         GraphicsDevice.PresentationParameters.BackBufferFormat, DepthFormat.Depth24);
+      lightingTarget = new RenderTarget2D(
+        GraphicsDevice, camera.Width, camera.Height, false /* mipmap */,
+        GraphicsDevice.PresentationParameters.BackBufferFormat, DepthFormat.Depth24);
+
+      lightingEffect = new BasicEffect(GraphicsDevice);
+      lightingEffect.World = Matrix.CreateTranslation(0, 0, 0);
+      lightingEffect.View = Matrix.CreateLookAt(Vector3.Backward, Vector3.Zero, Vector3.Up);
+      lightingEffect.VertexColorEnabled = true;
+
+      RasterizerState rasterizerState = new RasterizerState() {
+        CullMode = CullMode.None
+      };
+      GraphicsDevice.RasterizerState = rasterizerState;
 
       base.Initialize();
     }
@@ -67,7 +83,7 @@ namespace SemiColinGames {
       font = Content.Load<SpriteFont>("font");
 
       player = new Player(Content.Load<Texture2D>("Ninja_Female"));
-      world = new World(Content.Load<Texture2D>("grassland"), Levels.DEMO);
+      world = new World(Content.Load<Texture2D>("grassland"), Levels.ONE_ONE);
       grasslandBg1 = Content.Load<Texture2D>("grassland_bg1");
       grasslandBg2 = Content.Load<Texture2D>("grassland_bg2");
     }
@@ -131,8 +147,8 @@ namespace SemiColinGames {
 
       Debug.SetFpsText(fpsText);
 
-      // Draw scene to RenderTarget.
+      // Draw scene to sceneTarget.
-      GraphicsDevice.SetRenderTarget(renderTarget);
+      GraphicsDevice.SetRenderTarget(sceneTarget);
       GraphicsDevice.Clear(Color.CornflowerBlue);
       spriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null);
 
@@ -148,7 +164,8 @@ namespace SemiColinGames {
 
       // Set up transformation matrix for drawing world objects.
       Matrix transform = Matrix.CreateTranslation(-camera.Left, -camera.Top, 0);
-      spriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null, null, transform);
+      spriteBatch.Begin(
+          SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null, null, transform);
 
       // Draw player.
       player.Draw(spriteBatch);
@@ -162,7 +179,13 @@ namespace SemiColinGames {
       // Aaaaand we're done.
       spriteBatch.End();
 
-      // Draw RenderTarget to screen.
+      // Draw lighting to lightingTarget.
+      GraphicsDevice.SetRenderTarget(lightingTarget);
+      GraphicsDevice.Clear(new Color(0, 0, 0, 0f));
+      lightingEffect.Projection = camera.Projection;
+      DrawFov();
+
+      // Draw sceneTarget to screen.
       GraphicsDevice.SetRenderTarget(null);
       GraphicsDevice.Clear(Color.CornflowerBlue);
       if (framesToSuppress == 0) {
@@ -171,7 +194,8 @@ namespace SemiColinGames {
               RasterizerState.CullNone);
         Rectangle drawRect = new Rectangle(
           0, 0, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height);
-        spriteBatch.Draw(renderTarget, drawRect, Color.White);
+        spriteBatch.Draw(sceneTarget, drawRect, Color.White);
+        spriteBatch.Draw(lightingTarget, drawRect, Color.White);
 
         // Draw debug toasts.
         Debug.DrawToasts(spriteBatch, font);
@@ -182,5 +206,77 @@ namespace SemiColinGames {
       base.Draw(gameTime);
       drawTimer.Stop();
     }
+
+    private void DrawFov() {
+      // TODO: DrawIndexedPrimitives
+      Color color = Color.FromNonPremultiplied(new Vector4(0, 0, 1, 0.6f));
+      Vector2 eyePos = player.EyePosition;
+      int numConePoints = 60;
+      // TODO: don't new[] every frame.
+      VertexPositionColor[] conePoints = new VertexPositionColor[numConePoints];
+      float visionRange = 150;
+      float visionRangeSq = visionRange * visionRange;
+      float fov = FMath.DegToRad(120);
+      float fovStep = fov / (numConePoints - 1);
+
+      Vector2 ray = new Vector2(visionRange * player.GetFacing, 0);
+      if (player.GetPose == Player.Pose.Stretching) {
+        ray = ray.Rotate(player.GetFacing * FMath.DegToRad(-30));
+      }
+      if (player.GetPose == Player.Pose.Crouching) {
+        ray = ray.Rotate(player.GetFacing * FMath.DegToRad(30));
+      }
+
+      for (int i = 0; i < conePoints.Length; i++) {
+        float angle = -fov / 2 + fovStep * i;
+        Vector2 rotated = ray.Rotate(angle);
+        Vector2 closestHit = Vector2.Add(eyePos, rotated);
+        float hitTime = 1f;
+
+        Vector2 halfTileSize = new Vector2(World.TileSize / 2.0f, World.TileSize / 2.0f);
+        for (int j = 0; j < world.CollisionTargets.Length; j++) {
+          AABB box = world.CollisionTargets[j];
+          if (Math.Abs(box.Position.X - player.Position.X) > visionRange + halfTileSize.X) {
+            continue;
+          }
+          Vector2 delta = Vector2.Add(halfTileSize, Vector2.Subtract(box.Position, eyePos));
+          if (delta.LengthSquared() > visionRangeSq) {
+            continue;
+          }
+          Hit? maybeHit = box.IntersectSegment(eyePos, rotated);
+          if (maybeHit != null) {
+            Hit hit = maybeHit.Value;
+            if (hit.Time < hitTime) {
+              hitTime = hit.Time;
+              closestHit = hit.Position;
+            }
+          }
+        }
+
+        float tint = 0.6f - hitTime / 2;
+        Color tinted = Color.FromNonPremultiplied(new Vector4(0, 0, 1, tint));
+        conePoints[i] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
+      }
+
+      // TODO: don't new[] every frame.
+      VertexPositionColor[] vertices = new VertexPositionColor[numConePoints * 3];
+      VertexPositionColor eyeVertex = new VertexPositionColor(new Vector3(eyePos, 0), color);
+      for (int i = 0; i < numConePoints - 1; i++) {
+        vertices[i * 3] = eyeVertex;
+        vertices[i * 3 + 1] = conePoints[i];
+        vertices[i * 3 + 2] = conePoints[i + 1];
+      }
+
+      VertexBuffer vertexBuffer = new VertexBuffer(
+          GraphicsDevice, typeof(VertexPositionColor), vertices.Length, BufferUsage.WriteOnly);
+      vertexBuffer.SetData<VertexPositionColor>(vertices);
+
+      GraphicsDevice.SetVertexBuffer(vertexBuffer);
+
+      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
+        pass.Apply();
+        GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, vertices.Length / 3);
+      }
+    }
   }
 }