Course 3D_XNA: 3D-Computer Graphics with XNA Chapter C1: Moving Triangles Copyright © by V. Miszalok, last update: 25-09-2010
Let me know what you think	Project triangle1   Game1, Initialize, Update, Draw   Three triangles   Hundred triangles   Chaos   Help

This project is the XNA-clone of
3D-Computer Graphics with Managed DirectX, Chapter C1: Moving Triangles and of
3D-Computer Graphics with C++ and OpenGL, Chapter C1: Moving Triangles.

Project triangle1

This chapter requires no DirectX SDK but:
1. Visual C# 2010 Express or Visual Studio 2010 Professional
2. XNA Game Studio 4.0
3. DirectX End-User Runtimes

1. Main Menu after starting VS 2010: File → New Project... → Project types: XNA GameStudio 4.0 → Templates: Windows Game (4.0) → Name: triangle1 → Location: C:\temp → Create directory for solution: switch it off → OK.
Solution Explorer - triangle1: Delete the file Program.cs and the default code of Game1.cs.

2. If You find no Solution Explorer-window, open it via the main menu: View → Solution Explorer.
Inside the Solution Explorer-window click the plus-sign in front of triangle1. A tree opens. Look for the branch "References". Check if there are four references Microsoft.XNA.Framework, Microsoft.XNA.Framework.Game, mscorlib and System.

3. You should switch off the vexatious automatic format- and indent- mechanism of the code editor before You copy the following code to triangle1.cs (otherwise all the code will be reformatted into chaos):
3.1. Main menu of Visual C# 2010 Express: click menu "Tools".
3.2. A DropDown-menu appears. Click "Options...".
3.3. An Options dialog box appears.
3.4. Double click the branch "Text Editor" → double click "C#" → double click "Formatting".
3.5. A sub-tree appears with the 5 branches "General, Indentation, New Lines, Spacing, Wrapping".
3.6. Uncheck any of the 45 check boxes that these 5 Formatting-branches may offer.
3.7. Leave the dialog box with button "OK".

Game1, Initialize, Update, Draw

Write the following code into the empty code window of Game1.cs:

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

static class Program
{ static void Main() { Game1 game = new Game1(); game.Run(); }

public class Game1 : Microsoft.Xna.Framework.Game
{ private GraphicsDeviceManager g;
  private VertexBuffer vbuffer;
  private BasicEffect  effect;
  private EffectPass   pass;
  private float rotAngle = 0f;

  public Game1()
  { Window.Title = "3DTriangleAnimation";
    Window.AllowUserResizing = true;
    g = new GraphicsDeviceManager( this );
    g.IsFullScreen = false;
    g.PreferredBackBufferWidth  = 300;
    g.PreferredBackBufferHeight = 300;
  }
  protected override void Initialize()
  { VertexPositionColor[] v = new VertexPositionColor[3];
    v[0].Position.X=-1f; v[0].Position.Y=-1f; v[0].Position.Z=0f;
    v[1].Position.X= 0f; v[1].Position.Y= 0f; v[1].Position.Z=0f;
    v[2].Position.X= 1f; v[2].Position.Y=-1f; v[2].Position.Z=0f;
    v[0].Color = Color.Blue;
    v[1].Color = Color.Cornsilk;
    v[2].Color = Color.MediumOrchid;
    vbuffer = new VertexBuffer( g.GraphicsDevice, typeof(VertexPositionColor), 3, BufferUsage.WriteOnly );
    vbuffer.SetData< VertexPositionColor >( v );
    effect = new BasicEffect( g.GraphicsDevice, null );
    //effect.View = Matrix.CreateLookAt( new Vector3(0, 0, 3), Vector3.Zero, Vector3.Up );
    //effect.Projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.Pi/4, 1f, 1f, 10f );
    effect.VertexColorEnabled = true;
    pass = effect.CurrentTechnique.Passes[0];
  }
  protected override void Update( GameTime gameTime )
  { g.GraphicsDevice.Vertices[0].SetSource( vbuffer, 0, VertexPositionColor.SizeInBytes );
    g.GraphicsDevice.VertexDeclaration = new VertexDeclaration( g.GraphicsDevice, VertexPositionColor.VertexElements );
    //g.GraphicsDevice.RenderState.CullMode = CullMode.None;
  }
  protected override void Draw( GameTime gameTime )
  { //g.GraphicsDevice.Clear( Color.DarkBlue );
    //effect.World = Matrix.CreateRotationY( rotAngle += 0.01f );
    effect.Begin();
      pass.Begin();
        try { g.GraphicsDevice.DrawPrimitives( PrimitiveType.TriangleList, 0, 1 ); } catch {}
      pass.End();
    effect.End();
  }
} // end of class Game1
} // end of class Program

Click Debug → Start Without Debugging Ctrl F5. Drag the window borders.

Enhancements: (Start Without Debugging Ctrl F5 after any change.)

Keep all enhancements.
Experiments: (Recover the change after any experiment.)

Three triangles

Declare 4 new global variables in the head of public class Game1 : Microsoft.Xna.Framework.Game just below the line float rotationAngle = 0f;:

  private Matrix rot        = Matrix.CreateRotationY( 0f );
  private Matrix zoom       = Matrix.CreateScale( 0.5f );
  private Matrix leftshift  = Matrix.CreateTranslation( new Vector3( -1f, 0f, 0f ) );
  private Matrix rightshift = Matrix.CreateTranslation( new Vector3(  1f, 0f, 0f ) );

Change the protected override void Draw( GameTime gameTime )-function as follows:

  protected override void Draw( GameTime gameTime )
  { g.GraphicsDevice.Clear( Color.DarkBlue );
    rot = Matrix.CreateRotationY( rotAngle += 0.01f );
    //rot = Matrix.CreateFromYawPitchRoll( rotAngle += 0.01f, rotAngle, rotAngle );
    effect.Begin();
      pass.Begin();
        effect.World = rot;
        try { g.GraphicsDevice.DrawPrimitives( PrimitiveType.TriangleList, 0, 1 ); } catch {}
      pass.End();
      pass.Begin();
        effect.World = zoom * rot * leftshift;
        try { g.GraphicsDevice.DrawPrimitives( PrimitiveType.TriangleList, 0, 1 ); } catch {}
      pass.End();
      pass.Begin();
        effect.World = zoom * rot * rightshift;
        try { g.GraphicsDevice.DrawPrimitives( PrimitiveType.TriangleList, 0, 1 ); } catch {}
      pass.End();
    effect.End();
  }

Click Debug → Start Without Debugging Ctrl F5. Drag the window borders.
Experiments: (Recover the change after any experiment.)

Hundred triangles

Add the following declarations to the head of public class Game1 : Microsoft.Xna.Framework.Game below the line: Matrix rightshift=Matrix.CreateTranslation(new Vector3(1f,0f,0f));:

  private const Int32 nTriangles = 100;
  private float[] dx = new float[nTriangles];
  private float[] dy = new float[nTriangles];
  private float[] dz = new float[nTriangles];
  private float[] ax = new float[nTriangles];
  private float[] ay = new float[nTriangles];
  private float[] az = new float[nTriangles];
  private Random r = new Random();

Add the following intialisations to protected override void Initialize() below the line: pass = effect.CurrentTechnique.Passes[0];.

    for ( int i = 0; i < nTriangles; i++ )
    { dx[i] = (float)r.NextDouble() - 0.5f;  //random permanent translation dx
      dy[i] = (float)r.NextDouble() - 0.5f;  //random permanent translation dy
      dz[i] = (float)r.NextDouble() - 0.5f;  //random permanent translation dz
    }

    g.GraphicsDevice.RenderState.DepthBufferEnable = false;
    g.GraphicsDevice.RenderState.DepthBufferWriteEnable = false;

Change the protected override void Draw( GameTime gameTime ) - function as follows:

  protected override void Draw( GameTime gameTime )
  { g.GraphicsDevice.Clear( Color.DarkBlue );
    rot = Matrix.CreateFromYawPitchRoll( rotAngle += 0.01f, rotAngle, rotAngle );
    effect.Begin();
      for ( int i = 0; i < nTriangles; i++ )
      { pass.Begin();
          leftshift = Matrix.CreateTranslation( dx[i], dy[i], dz[i] );
          effect.World = zoom * rot * leftshift;
          try { g.GraphicsDevice.DrawPrimitives( PrimitiveType.TriangleList, 0, 1 ); } catch {}
        pass.End();
      }
    effect.End();
  }

Click Debug → Start Without Debugging Ctrl F5. Hundred small triangles will dance synchronously as fishes do.

Chaos

Change protected override void Initialize() below the line: pass = effect.CurrentTechnique.Passes[0]; as follows:

    for ( int i = 0; i < nTriangles; i++ )
    { dx[i] = (float)r.NextDouble() - 0.5f;  //random permanent translation dx
      dy[i] = (float)r.NextDouble() - 0.5f;  //random permanent translation dy
      dz[i] = (float)r.NextDouble() - 0.5f;  //random permanent translation dz
      ax[i] = (float)r.NextDouble(); //random initial pitch rotation angle
      ay[i] = (float)r.NextDouble(); //random initial yaw   rotation angle
      az[i] = (float)r.NextDouble(); //random initial roll  rotation angle
    }
    g.GraphicsDevice.RenderState.DepthBufferEnable      = false;
    g.GraphicsDevice.RenderState.DepthBufferWriteEnable = false;

Change the protected override void Draw( GameTime gameTime ) - function as follows:

  protected override void Draw( GameTime gameTime )
  { g.GraphicsDevice.Clear( Color.DarkBlue );
    effect.Begin();
      for ( int i = 0; i < nTriangles; i++ )
      { pass.Begin();
          rot = Matrix.CreateFromYawPitchRoll( ay[i] += 0.01f, ax[i] += 0.01f, az[i] += 0.01f );
          leftshift = Matrix.CreateTranslation( dx[i], dy[i], dz[i] );
          effect.World = zoom * rot * leftshift;
          g.GraphicsDevice.DrawPrimitives( PrimitiveType.TriangleList, 0, 1 );
        pass.End();
      }
    effect.End();
  }

Click Debug → Start Without Debugging Ctrl F5. Hundred small triangles will dance as flying paper sheets do.

Experiments: (Recover the change after any experiment.)

1.	Allow the default Z-test and put comment slashes // in front of both g.GraphicsDevice.RenderState.DepthBufferEnable = false; and g.GraphicsDevice.RenderState.DepthBufferWriteEnable = false;. Keep this change.	New triangles don't cover the old ones.
2.	Vary the constant const Int32 nTriangles = 100; between 10 and 1000.	Less or more triangles.
3.	Vary the random initial pitch+yaw+roll rotation angles ax[i], ay[i], az[i] inside the constructor between 0f and (float)(2 * Math.PI * r.NextDouble()).	The initial disorder changes.
4.	Vary the retarding factors 0.01f inside Matrix.CreateFromYawPitchRoll of the angular increments ay[i], ax[i] and az[i] between 0.001f and 0.1f.	Less or more chaos.
5.	Insert a new line just below pass.Begin();: zoom = Matrix.CreateScale( new Vector3( (float)r.NextDouble(), (float)r.NextDouble(), (float)r.NextDouble() ) );.	Bustling excitement.

Help

1. I recommend the following german booklet: KONEROW Jens: XNA Framework. schnell + kompakt, entwickler.press, ISBN: 978-3-939084-53-2,  € 7,90 (130 pages) and the code of Konerow's samples from the link "Quellcode" or everything as e-book, € 6,70.

2. You find extensive information about XNA here: http://msdn2.microsoft.com/en-us/library/bb200104.aspx.
Click trough the tree on the left side:
1: XNA Game Studio x.0 → Getting Started with XNA Game Studio → Your First Game: Microsoft XNA Game Studio in 2D
2: XNA Game Studio x.0 → Programming Guide
3: XNA Game Studio x.0 → XNA Framework Class Library Reference

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