Aspect ratio problem by using Matrix

Thank you for quick response. After the angle value is changed from degree to radians, the problem is still not solved. Here is a simple program.

using System;
using System.Drawing;
using System.Windows.Forms;

using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL;

namespace openTK_test_01
{
public partial class Form1 : Form
{
private bool loaded1 = false;
private int h;
private int w;

public Form1()
{
InitializeComponent();
}

private void glControl1_Load(object sender, EventArgs e)
{
loaded1 = true;
GL.ClearColor(Color.Black);
w = glControl1.Width;
h = glControl1.Height;
}

private void glControl1_Resize(object sender, EventArgs e)
{
if (!loaded1)
return;

GL.MatrixMode(MatrixMode.Projection);
GL.LoadIdentity();

w = glControl1.Width;
h = glControl1.Height;

Matrix4d m_perspective = Matrix4d.CreatePerspectiveFieldOfView(Math.PI / 4.0, (double)w / (double)h, 1.0, 40.0);
GL.LoadMatrix(ref m_perspective);
GL.Viewport(0, 0, w, h);
glControl1.Refresh();
}

private void glControl1_Paint(object sender, PaintEventArgs e)
{
if (!loaded1)
return;

DisplayViewPort();
glControl1.SwapBuffers();
}

private void DisplayViewPort()
{
GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
GL.LoadIdentity();

GL.MatrixMode(MatrixMode.Modelview);
//
// Draw a triangle
//
GL.Begin(BeginMode.Triangles);
GL.Color3(0.8f, 0.1f, 0.5f);
GL.Vertex3(0.2, 0.0, 0.0);
GL.Color3(0.1f, 0.8f, 0.5f);
GL.Vertex3(0.0, 1.0, 0.0);
GL.Color3(0.1f, 0.5f, 0.8f);
GL.Vertex3(-0.2, 0.0, 0.0);
GL.End();
//
//Switch to the drawing perspective
//
GL.Begin(BeginMode.Lines);
GL.Color3(0.1f, 0.8f, 0.5f);
GL.Vertex3(-0.5 * w, 0.0f, 0.0f);
GL.Vertex3(0.5 * w, 0.0f, 0.0f);

GL.Vertex3(0.0f, -0.5 * h, 0.0f);
GL.Vertex3(0.0f, 0.5 * h, 0.0f);
GL.End();
}
}
}

Run program and resize the window, you will notice that the triangle shape will be changed when ratio of w / h is changed. I am trying to keep object shape unchange even when w / h is changed. Your help is surely appreciated.

jjgl, please select your sourcecode and click on the "C#"- button to enable syntax highlighting, nobody will read it like in notepad.

Sure, that is simple (I am using floats, you see):

    /// <summary> /// Client-window is resized /// </summary>
    protected override void OnResize(EventArgs e)
    {
      base.OnResize(e);
 
      GL.Viewport(ClientRectangle.X, ClientRectangle.Y, ClientRectangle.Width, ClientRectangle.Height);
      Matrix4 projection = Matrix4.CreatePerspectiveFieldOfView((float)Math.PI / 4,  Width / (float)Height, 0.1f, 500.0f);
      GL.MatrixMode(MatrixMode.Projection);
      GL.LoadMatrix(ref projection);
    }

Or you can use the search-function, you can find many examples here.

If it is so simple, why do you not write it yourself?

Thread should be moved, not an issue of OpenTK.

Hi, ...

True, there is a problem ...

I modified the code as follows:

using System;
using System.Drawing;
using System.Windows.Forms;
 
using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL;
 
namespace openTK_test_01
{
    public partial class Form1 : Form
    {
        private bool loaded1 = false;
        private int h;
        private int w;
 
        public Form1()
        {
            InitializeComponent();
        }
 
        private void glControl1_Load(object sender, EventArgs e)
        {
            loaded1 = true;
            GL.ClearColor(Color.Black);
            w = glControl1.Width;
            h = glControl1.Height;
        }
 
        internal void gluPerspective(double fovy, double aspect, double zNear, double zFar)
        {
            double xmin, xmax, ymin, ymax;
 
            ymax = zNear * Math.Tan(fovy * Math.PI / 360.0);
            ymin = -ymax;
 
            xmin = ymin * aspect;
            xmax = ymax * aspect;
 
            GL.Frustum(xmin, xmax, ymin, ymax, zNear, zFar);
        }
 
        private void glControl1_Resize(object sender, EventArgs e)
        {
            //if (!loaded1)
            //    return;
            //base.OnResize(e);
 
            h = glControl1.Height;
            w = glControl1.Width;
            GL.Viewport(0, 0, w, h);
 
            //Matrix4 m_perspective = Matrix4.CreatePerspectiveFieldOfView((float)(Math.PI / 4.0f), w / (float)h, 0.1f, 200.0f);
            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadIdentity();
            gluPerspective(45.0, w/(float)h, 0.1, 400.0);
            //GL.LoadMatrix(ref m_perspective);
            //glControl1.Refresh();
        }
 
 
        private void glControl1_Paint(object sender, PaintEventArgs e)
        {
            //if (!loaded1)
            //    return;
            GL.MatrixMode(MatrixMode.Modelview);
            GL.LoadIdentity();
 
            GL.Enable(EnableCap.DepthTest);
 
            DisplayViewPort();
            glControl1.SwapBuffers();
        }
 
        private void DisplayViewPort()
        {
            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
 
            //
            //Switch to the drawing perspective
            //
 
            GL.Translate(0, 0, -10);
            //
            // Draw a triangle
            //
            GL.Begin(BeginMode.Triangles);
            GL.Color3(0.8f, 0.1f, 0.5f);
            GL.Vertex3(0.2, 0.0, 0.0);
            GL.Color3(0.1f, 0.8f, 0.5f);
            GL.Vertex3(0.0, 1.0, 0.0);
            GL.Color3(0.1f, 0.5f, 0.8f);
            GL.Vertex3(-0.2, 0.0, 0.0);
            GL.End();
 
            GL.Begin(BeginMode.Lines);
            GL.Color3(0.1f, 0.8f, 0.5f);
            GL.Vertex3(-0.5 * w, 0.0f, 0.0f);
            GL.Vertex3(0.5 * w, 0.0f, 0.0f);
 
            GL.Vertex3(0.0f, -0.5 * h, 0.0f);
            GL.Vertex3(0.0f, 0.5 * h, 0.0f);
            GL.End();
        }
    }
}

The problem is that when it reduces both the width and height of the control, just call the Resize method () of control, but the paint () method of control is not called.

In another case, when increasing the width or height of the control, everything works fine, first resize () method of control is called and then the paint () method of control is called.

Using OpenTK 1.0 branch ...
Is a Bug ...

Regards, ...

Hm got to look that up, but think I've always used .Invalidate() as last call in the resize function since this flags the control contents as now-invalid and calls paint as necessary.