An OpenGL Control

What we need to do now is add a class named OurView. Make it a derived class from OpenGLControl. I will show you the code for the class now.

using System;
using System.Drawing;
using System.Windows.Forms;
using CsGL.OpenGL;
namespace SimpleOpenGL
{
    public class OurView : OpenGLControl
    {
        public OurView(): base()
        {
            this.KeyDown += new KeyEventHandler(OurView_OnKeyDown);
        }
        public override void glDraw()
        {    
            GL.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer    
            GL.glLoadIdentity();                 // Reset The Current Modelview Matrix        
            // TODO: Draw a box or something
//             this.SwapBuffer(); // swap Buffers
        }
        protected override void InitGLContext()
        {
            GL.glShadeModel(GL.GL_SMOOTH);         // Set Smooth Shading                
            GL.glClearColor(0.0f, 0.0f, 0.0f, 0.5f);     // BackGround Color        
            GL.glClearDepth(1.0f);                 // Depth buffer setup            
            GL.glEnable(GL.GL_DEPTH_TEST);         // Enables Depth Testing            
            GL.glDepthFunc(GL.GL_LEQUAL);             // The Type Of Depth Test To Do    
            GL.glHint(GL.GL_PERSPECTIVE_CORRECTION_HINT, GL.GL_NICEST);     /* Really Nice Perspective Calculations */    
        }
        protected override void OnSizeChanged(EventArgs e)
        {
            base.OnSizeChanged(e);
       
            Size s = Size;
            double aspect_ratio = (double)s.Width /(double) s.Height;
            GL.glMatrixMode(GL.GL_PROJECTION); // Select The Projection Matrix
            GL.glLoadIdentity(); // Reset The Projection Matrix
           
            // Calculate The Aspect Ratio Of The Window
            GL.gluPerspective(45.0f, aspect_ratio, 0.1f, 100.0f);
   
            GL.glMatrixMode(GL.GL_MODELVIEW); // Select The Modelview Matrix
            GL.glLoadIdentity();// Reset The Modelview Matrix
        }
        protected void OurView_OnKeyDown(object Sender, KeyEventArgs kea)
        {
            if (kea.KeyCode == Keys.Q && kea.Modifiers == Keys.Shift)
            {
                Application.Exit();
            }
        }
    }
}

You may notice that this is almost the base code from NeHe. And yes it is I created it with the NeHe base code in mind. I won’t go for every gl function in detail you can read here, lesson 1 & 2 for that.

Now we have the control we can add it to our form. Add this in the class

private SimpleOpenGL.OurView view;

Ok add this after the InitializeComponent function.

this.view = new SimpleOpenGL.OurView();
this.view.Parent = this;
this.view.Dock = DockStyle.Fill; // Will fill whole form

You can now try to run your form. Everything is running perfect. But there is one more thing our form is only render once. And when you resize it, it will render another time. To solve this problem we’re going to add a thread which will render the scene over and over again (how it should).

Ok first thing to do is add a thread. Put this underneath the other declarations.

private static Thread thrOpenGL;

Then underneath the view properties.

thrOpenGL = new Thread(new ThreadStart(OpenGL_Start));
thrOpenGL.Start();
Then the function OpenGL_Start.
private void OpenGL_Start()
{
    for (;;) // infinity loop for rendering
    {
        this.view.Refresh();
    }
}

If you would run the application now you might notice that when you close the form you program isn’t really exit cause the thread is still running to solve this we add this code at the end of the Dispose function. But for people who don’t use the Visual Studio .Net I will show you the whole function.

protected override void Dispose( bool disposing )
{
    if( disposing )
    {
        if (components != null)
        {
            components.Dispose();
        }
    }
    base.Dispose( disposing );
    // Abort the OpenGL Thread
    // otherwise it will last rendering forever
    thrOpenGL.Abort();
}

We are done with our OpenGL control now but it is hard to show off to your friends when you only have a black window. Like this.BackColor = Color.Black;in the main form constructor will do the same thing.