From df436f8c32a77db88f3ee36d2d55beec33c2e37a Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Wed, 15 Jul 2020 15:56:56 -0400
Subject: [PATCH] TreeScene: draw a triangle

---
 Shared/SneakGame.cs |  8 ++++----
 Shared/TreeScene.cs | 33 +++++++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/Shared/SneakGame.cs b/Shared/SneakGame.cs
index 05d0946..890969d 100644
--- a/Shared/SneakGame.cs
+++ b/Shared/SneakGame.cs
@@ -64,11 +64,11 @@ namespace SemiColinGames {
 
     private void LoadLevel() {
       world?.Dispose();
-      world = new SneakWorld(GraphicsDevice, Content.LoadString("levels/demo.json"));
-      // world = new TreeWorld();
+      // world = new SneakWorld(GraphicsDevice, Content.LoadString("levels/demo.json"));
+      world = new TreeWorld();
       scene?.Dispose();
-      scene = new SneakScene(GraphicsDevice, ((SneakWorld) world).Camera);
-      // scene = new TreeScene(GraphicsDevice);
+      // scene = new SneakScene(GraphicsDevice, ((SneakWorld) world).Camera);
+      scene = new TreeScene(GraphicsDevice);
 
       GC.Collect();
       GC.WaitForPendingFinalizers();
diff --git a/Shared/TreeScene.cs b/Shared/TreeScene.cs
index 230f568..aa09841 100644
--- a/Shared/TreeScene.cs
+++ b/Shared/TreeScene.cs
@@ -6,12 +6,28 @@ using System;
 namespace SemiColinGames {
   public sealed class TreeScene : IScene {
 
-    readonly Color backgroundColor = Color.SkyBlue;
+    const int MAX_LINE_VERTICES = 4;
 
-    readonly GraphicsDevice graphics;
+    private readonly Color backgroundColor = Color.SkyBlue;
+    private readonly GraphicsDevice graphics;
+    private readonly BasicEffect basicEffect;
+
+    private VertexPositionColor[] lineVertices;
+    private VertexBuffer vertexBuffer;
 
     public TreeScene(GraphicsDevice graphics) {
       this.graphics = graphics;
+
+      basicEffect = new BasicEffect(graphics) {
+        World = Matrix.CreateTranslation(0, 0, 0),
+        View = Matrix.CreateLookAt(Vector3.Backward, Vector3.Zero, Vector3.Up),
+        VertexColorEnabled = true
+      };
+      basicEffect.Projection = Matrix.CreateOrthographicOffCenter(0, 1920, 1080, 0, -1, 1);
+
+      lineVertices = new VertexPositionColor[MAX_LINE_VERTICES];
+      vertexBuffer = new VertexBuffer(
+          graphics, typeof(VertexPositionColor), MAX_LINE_VERTICES, BufferUsage.WriteOnly);
     }
 
     ~TreeScene() {
@@ -19,11 +35,24 @@ namespace SemiColinGames {
     }
 
     public void Dispose() {
+      vertexBuffer.Dispose();
       GC.SuppressFinalize(this);
     }
 
     public void Draw(bool isRunningSlowly, IWorld iworld, bool paused) {
       graphics.Clear(backgroundColor);
+
+      lineVertices[0] = new VertexPositionColor(new Vector3(100, 100, 0), Color.Black);
+      lineVertices[1] = new VertexPositionColor(new Vector3(300, 200, 0), Color.Black);
+      lineVertices[2] = new VertexPositionColor(new Vector3(200, 200, 0), Color.Black);
+      lineVertices[3] = new VertexPositionColor(new Vector3(100, 100, 0), Color.Black);
+
+      graphics.SetVertexBuffer(vertexBuffer);
+      vertexBuffer.SetData(lineVertices);
+      foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes) {
+        pass.Apply();
+        graphics.DrawPrimitives(PrimitiveType.LineStrip, 0, 3 /* num lines */);
+      }
     }
   }
 }
\ No newline at end of file