From d6addc15e0aec32f8b6e3334f42f50870c06d639 Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Thu, 16 Jul 2020 11:34:10 -0400
Subject: [PATCH] Draw basic trapezoidal skeleton.

---
 Shared/TreeScene.cs | 61 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 13 deletions(-)

diff --git a/Shared/TreeScene.cs b/Shared/TreeScene.cs
index aa09841..5dd5915 100644
--- a/Shared/TreeScene.cs
+++ b/Shared/TreeScene.cs
@@ -1,18 +1,19 @@
 using Microsoft.Xna.Framework;
-using Microsoft.Xna.Framework.Audio;
 using Microsoft.Xna.Framework.Graphics;
 using System;
+using System.Collections.Generic;
 
 namespace SemiColinGames {
   public sealed class TreeScene : IScene {
 
-    const int MAX_LINE_VERTICES = 4;
+    const int MAX_SEGMENTS = 1000;
+    const int MAX_VERTICES = MAX_SEGMENTS * 6;  // 2 triangles per segment
 
     private readonly Color backgroundColor = Color.SkyBlue;
     private readonly GraphicsDevice graphics;
     private readonly BasicEffect basicEffect;
 
-    private VertexPositionColor[] lineVertices;
+    private VertexPositionColor[] vertices;
     private VertexBuffer vertexBuffer;
 
     public TreeScene(GraphicsDevice graphics) {
@@ -21,13 +22,13 @@ namespace SemiColinGames {
       basicEffect = new BasicEffect(graphics) {
         World = Matrix.CreateTranslation(0, 0, 0),
         View = Matrix.CreateLookAt(Vector3.Backward, Vector3.Zero, Vector3.Up),
-        VertexColorEnabled = true
+        VertexColorEnabled = true,
+        Projection = Matrix.CreateOrthographicOffCenter(-1920 / 2, 1920 / 2, -1080 / 4, 1080 * 3 / 4, -1, 1)
       };
-      basicEffect.Projection = Matrix.CreateOrthographicOffCenter(0, 1920, 1080, 0, -1, 1);
 
-      lineVertices = new VertexPositionColor[MAX_LINE_VERTICES];
+      vertices = new VertexPositionColor[MAX_VERTICES];
       vertexBuffer = new VertexBuffer(
-          graphics, typeof(VertexPositionColor), MAX_LINE_VERTICES, BufferUsage.WriteOnly);
+          graphics, typeof(VertexPositionColor), MAX_VERTICES, BufferUsage.WriteOnly);
     }
 
     ~TreeScene() {
@@ -39,19 +40,53 @@ namespace SemiColinGames {
       GC.SuppressFinalize(this);
     }
 
+    public struct Trapezoid {
+      public Vector2 p1, p2, p3, p4;
+    }
+
     public void Draw(bool isRunningSlowly, IWorld iworld, bool paused) {
+      var skeleton = new List<Vector2> {
+        new Vector2(0, 0),
+        new Vector2(0, 100),
+        new Vector2(10, 200),
+        new Vector2(30, 300),
+        new Vector2(60, 400),
+        new Vector2(100, 500),
+      };
+
       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);
+      var segments = new List<Trapezoid>();
+
+      for (int i = 0; i < skeleton.Count - 1; i++) {
+        Vector2 low = skeleton[i];
+        Vector2 high = skeleton[i + 1];
+        Trapezoid t;
+        int width = 10 - i;
+        t.p1 = new Vector2(low.X - width, low.Y);
+        t.p2 = new Vector2(low.X + width, low.Y);
+        t.p3 = new Vector2(high.X - width + 4, high.Y);
+        t.p4 = new Vector2(high.X + width - 4, high.Y);
+        segments.Add(t);
+      }
+
+      Color color = Color.SaddleBrown;
+      for (int i = 0; i < segments.Count; i++) {
+        Trapezoid t = segments[i];
+        vertices[i * 6] = new VertexPositionColor(new Vector3(t.p1.X, t.p1.Y, 0), color);
+        vertices[i * 6 + 1] = new VertexPositionColor(new Vector3(t.p2.X, t.p2.Y, 0), color);
+        vertices[i * 6 + 2] = new VertexPositionColor(new Vector3(t.p3.X, t.p3.Y, 0), color);
+        vertices[i * 6 + 3] = new VertexPositionColor(new Vector3(t.p2.X, t.p2.Y, 0), color);
+        vertices[i * 6 + 4] = new VertexPositionColor(new Vector3(t.p3.X, t.p3.Y, 0), color);
+        vertices[i * 6 + 5] = new VertexPositionColor(new Vector3(t.p4.X, t.p4.Y, 0), color);
+      }
 
       graphics.SetVertexBuffer(vertexBuffer);
-      vertexBuffer.SetData(lineVertices);
+      vertexBuffer.SetData(vertices);
+
       foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes) {
         pass.Apply();
-        graphics.DrawPrimitives(PrimitiveType.LineStrip, 0, 3 /* num lines */);
+        graphics.DrawPrimitives(PrimitiveType.TriangleList, 0, segments.Count * 2);
       }
     }
   }