From 5d21ff2a0f9a7ffff913d7504532a2870cf5325f Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Sat, 15 Feb 2020 15:47:05 -0500
Subject: [PATCH] Debug.DrawLines: use GPU to draw lines.

Fixes #19.

GitOrigin-RevId: d837e0ddafa0b7ea66fea4bba05ca7412a3c5726
---
 Shared/Debug.cs        | 42 +++++++++++++++++++++++++++++-------------
 Shared/LinesOfSight.cs |  1 +
 Shared/SneakGame.cs    |  7 +++++--
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/Shared/Debug.cs b/Shared/Debug.cs
index 0167ee0..df02aa8 100644
--- a/Shared/Debug.cs
+++ b/Shared/Debug.cs
@@ -27,15 +27,22 @@ namespace SemiColinGames {
     }
 
     public static bool Enabled = true;
+    // Lines in excess of MAX_LINES get dropped on the floor.
+    const int MAX_LINES = 1000;
+    const int MAX_LINE_VERTICES = MAX_LINES * 2;
     // This is a LinkedList instead of a List because SetFpsText() adds to its front.
     static readonly LinkedList<string> toasts = new LinkedList<string>();
     static readonly List<DebugRect> rects = new List<DebugRect>();
-    static readonly List<DebugLine> lines = new List<DebugLine>();
+    static int lineIdx = 0;
+    static readonly VertexPositionColor[] lineVertices = new VertexPositionColor[MAX_LINE_VERTICES];
+    static VertexBuffer vertexBuffer;
 
     static Texture2D whiteTexture;
 
-    public static void Initialize(Texture2D white) {
+    public static void Initialize(GraphicsDevice graphics, Texture2D white) {
       whiteTexture = white;
+      vertexBuffer = new VertexBuffer(
+          graphics, typeof(VertexPositionColor), MAX_LINE_VERTICES, BufferUsage.WriteOnly);
     }
 
     public static void WriteLine(string s) {
@@ -50,7 +57,7 @@ namespace SemiColinGames {
       toasts.Clear();
       if (!paused) {
         rects.Clear();
-        lines.Clear();
+        lineIdx = 0;
       }
     }
 
@@ -75,15 +82,20 @@ namespace SemiColinGames {
     }
 
     public static void AddLine(Point start, Point end, Color color) {
-      lines.Add(new DebugLine(start, end, color));
+      if (lineIdx >= MAX_LINE_VERTICES) {
+        return;
+      }
+      lineVertices[lineIdx] = new VertexPositionColor(new Vector3(start.X, start.Y, 0), color);
+      lineVertices[lineIdx + 1] = new VertexPositionColor(new Vector3(end.X, end.Y, 0), color);
+      lineIdx += 2;
     }
 
     public static void AddLine(int p1x, int p1y, int p2x, int p2y, Color color) {
-      lines.Add(new DebugLine(new Point(p1x, p1y), new Point(p2x, p2y), color));
+      AddLine(new Point(p1x, p1y), new Point(p2x, p2y), color);
     }
 
     public static void AddLine(Vector2 start, Vector2 end, Color color) {
-      lines.Add(new DebugLine(start.ToPoint(), end.ToPoint(), color));
+      AddLine(start.ToPoint(), end.ToPoint(), color);
     }
 
     public static void DrawToasts(SpriteBatch spriteBatch, SpriteFont font) {
@@ -97,10 +109,13 @@ namespace SemiColinGames {
       }
     }
 
-    public static void Draw(SpriteBatch spriteBatch) {
+    public static void Draw(
+        SpriteBatch spriteBatch, GraphicsDevice graphics, BasicEffect lightingEffect) {
       if (!Enabled) {
         return;
       }
+
+      // Draw rects.
       foreach (var debugRect in rects) {
         var rect = debugRect.Rect;
         var color = debugRect.Color;
@@ -117,12 +132,13 @@ namespace SemiColinGames {
         spriteBatch.Draw(
           whiteTexture, new Rectangle(rect.Right - 1, rect.Top, 1, rect.Height), color);
       }
-      foreach (var line in lines) {
-        Point[] points = Line.Rasterize(line.Start, line.End);
-        foreach (var point in points) {
-          spriteBatch.Draw(
-            whiteTexture, new Rectangle(point.X, point.Y, 1, 1), line.Color);
-        }
+
+      // Draw lines.
+      graphics.SetVertexBuffer(vertexBuffer);
+      vertexBuffer.SetData(lineVertices);
+      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
+        pass.Apply();
+        graphics.DrawPrimitives(PrimitiveType.LineList, 0, lineIdx / 2);
       }
     }
   }
diff --git a/Shared/LinesOfSight.cs b/Shared/LinesOfSight.cs
index 5b325d0..6631ac3 100644
--- a/Shared/LinesOfSight.cs
+++ b/Shared/LinesOfSight.cs
@@ -35,6 +35,7 @@ namespace SemiColinGames {
         float angle = -fov / 2 + fovStep * i;
         Vector2 rotated = ray.Rotate(angle);
         Vector2 closestHit = Vector2.Add(eyePos, rotated);
+        Debug.AddLine(eyePos, closestHit, Color.Yellow);
         float hitTime = 1f;
 
         Vector2 halfTileSize = new Vector2(World.TileSize / 2.0f, World.TileSize / 2.0f);
diff --git a/Shared/SneakGame.cs b/Shared/SneakGame.cs
index c947daa..592c5d7 100644
--- a/Shared/SneakGame.cs
+++ b/Shared/SneakGame.cs
@@ -90,7 +90,7 @@ namespace SemiColinGames {
 
       whiteTexture = new Texture2D(GraphicsDevice, 1, 1);
       whiteTexture.SetData(new Color[] { Color.White });
-      Debug.Initialize(whiteTexture);
+      Debug.Initialize(GraphicsDevice, whiteTexture);
     }
 
     // Called once per game. Unloads all game content.
@@ -99,6 +99,8 @@ namespace SemiColinGames {
 
       updateTimer.DumpStats();
       drawTimer.DumpStats();
+
+      base.UnloadContent();
     }
 
     // Updates the game world.
@@ -182,7 +184,8 @@ namespace SemiColinGames {
       world.Draw(spriteBatch);
 
       // Draw debug rects & lines.
-      Debug.Draw(spriteBatch);
+      lightingEffect.Projection = camera.Projection;
+      Debug.Draw(spriteBatch, GraphicsDevice, lightingEffect);
 
       // Aaaaand we're done.
       spriteBatch.End();