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Rotation Sample

Posted by John O Donnell Articles | GDI+ & Graphics April 24, 2001
After reading Mike Golds article on transforms I thought I would get things moving a bit!
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Description of the Article

After reading Mike Golds article on transforms I thought I would get things moving a bit!

Overriding the OnPaint method and using the Timer class allows us to create a simple animation where we rotate a line around a central point.

Anyone want to create an asteroids clone in C#? 

Source Code:

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Drawing.Drawing2D;
namespace Rotationb2
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Timer timer1;
private System.ComponentModel.IContainer components;
public float f=0;
public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
this.timer1 = new System.Windows.Forms.Timer(this.components);
//
// timer1
//
this.timer1.Enabled = true;
this.timer1.Interval = 50;
this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(240, 221);
this.Name = "Form1";
this.Text = "Rotationb2";
}
#endregion
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main ()
{
Application.Run(new Form1());
}
protected override void OnPaint(PaintEventArgs e)
{
e.Graphics.DrawEllipse(Pens.Red,0,0,220,220);
GraphicsPath gp = new GraphicsPath();
gp.AddLine(30,30,110,110);
Matrix RotationTransform = new Matrix(1,0, 0,1,1,1); //rotation matrix
PointF TheRotationPoint = new PointF(110.0f, 110.0f); //rotation point
RotationTransform.RotateAt(f, TheRotationPoint);
gp.Transform(RotationTransform);
e.Graphics.DrawPath(Pens.Blue, gp);
f=f+10;
if (f==360)
f=0;
}
private void timer1_Tick(object sender, System.EventArgs e)
{
//force client window to be refreshed
this.Refresh();
}
}
}

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