sneak/Shared/TreeScene.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Graphics;
using System;

namespace SemiColinGames {
  public sealed class TreeScene : IScene {

    const int MAX_LINE_VERTICES = 4;

    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() {
      Dispose();
    }

    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 */);
      }
    }
  }
}