Perspective and Orthographic Problem

what are you wrong?

I guess it does not work if you remove that line?

I cannot see any specific error in your code ... try to remove stuff piece by piece see if anything happens

Of course, it works fine if I remove two pieces
GL.MatrixMode(MatrixMode.Projection);
GL.PushMatrix();
GL.LoadIdentity();
GL.Ortho(-width / 2, width / 2, -height / 2, height / 2, -1000, 1000); // works fine
// Glu.Perspective(45, width / height, 0.1, 100); // problem
GL.MatrixMode(MatrixMode.Modelview);
GL.PushMatrix();
GL.LoadIdentity();

and

GL.MatrixMode(MatrixMode.Projection);
GL.PopMatrix();
GL.MatrixMode(MatrixMode.Modelview);
GL.PopMatrix();

But that is not what i want. I want to get the world coordinates corresponding to the mouse click in the perspective projection (I print three values x, y, z out to a text box to check). With the Render (as I posted) and Window_Coor_To_World_Coor function

private Point3d Window_Coor_To_World_Coor(int x, int y) // x,y : x,y-coordinates of the mouse
{
Vector3 result = new Vector3();
GL.MatrixMode(MatrixMode.Projection);
GL.PushMatrix();
GL.LoadIdentity();

GL.Ortho(-width / 2, width / 2, -height / 2, height / 2, -1000, 1000); // works fine
// Glu.Perspective(45, width / height, 0.1, 100); // problem

GL.MatrixMode(MatrixMode.Modelview);
GL.PushMatrix();
GL.LoadIdentity();

int[] Viewport = new int[4];
double[] ModelViewMatrix = new double[16];
double[] ProjectionMatrix = new double[16];

GL.GetInteger(GetPName.Viewport, Viewport);
GL.GetDouble(GetPName.ModelviewMatrix, ModelViewMatrix);
GL.GetDouble(GetPName.ProjectionMatrix, ProjectionMatrix);

object t = x;
GL.ReadPixels(x, viewport[3] - y, 1, 1, PixelFormat.DepthComponent, PixelType.Float,t);
float z = (float)t;

Glu.UnProject(new Vector3(mouseX, viewport[3] - mouseY, 0), ModelViewMatrix, ProjectionMatrix, Viewport, out result);

GL.MatrixMode(MatrixMode.Projection);
GL.PopMatrix();
GL.MatrixMode(MatrixMode.Modelview);
GL.PopMatrix();

return result;
}

I got the right world coordinates with the line
GL.Ortho(-width / 2, width / 2, -height / 2, height / 2, -1000, 1000); // works fine
With
// Glu.Perspective(45, width / height, 0.1, 100); // problem
I can't see anything when i launch the scene.

Do you get my point ? I don't know why the Glu.Perspective doesn't work in this situation.

If the object is too far off into the scene, I can translate and zoom in the hold screen with mouse events. So the distance now is not a problem. I just want to have an exact perspective view for my scene. Can you give me some code for this ?

I've just changed 1,100 to 1,10000 in Glu.Perspective. I see only one line. This line is a part of the plane( a plane like in 3ds max) that I draw on the scene.