Question

I was trying to learn how to do openGL within a VB .NET environment and it seems that the Tao framework or OpenTK is recommended with OpenTK having a higher recommendation so that is what I chose to try using.

Since I am brand new to this, I am trying to just draw a simple box, triangle, or anything really so that I can understand it all before making more complex things. I have been unsuccessful at this so far so I will list in order what I have done so far and hopefully someone here can help me correct it or provide a new example just so I can draw a simple shape.

1) I installed OpenTK using opentk-2010-10-06.exe

2) In a new project I added the references to OpenTK.dll and OpenTK.Compatibility.dll

3) I added the control (opentk.glcontrol.dll)

4) I added the actual control to my form.

Using some examples online I added the rest:

5) I wrote my references in:

Imports OpenTK
Imports OpenTK.GLControl
Imports OpenTK.Platform
Imports OpenTK.Graphics.OpenGL
Imports System.Math

6) My global variable:

 Dim _STARTED As Boolean = False

7) I wrote my events:

Private Sub GlControl1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles GlControl1.Resize
_STARTED = True
ResizeGL()
End Sub

Private Sub ResizeGL()
    GL.Viewport(0, 0, GlControl1.Width, GlControl1.Height)
    GL.MatrixMode(MatrixMode.Projection) ' Select The Projection Matrix
    GL.MatrixMode(MatrixMode.Modelview) ' Select The Modelview Matrix
    GL.LoadIdentity() ' Reset The Modelview Matrix
End Sub


Public Sub ViewPerspective() ' Set Up A Perspective View

    GL.MatrixMode(MatrixMode.Projection) ' Select Projection
    GL.LoadIdentity() ';    
    Dim perspective1 As Matrix4 = OpenTK.Matrix4.CreatePerspectiveFieldOfView(MathHelper.PiOver4, _
                                         CSng((GlControl1.Width) / (GlControl1.Height)), 0.1, 1000)
    GL.LoadMatrix(perspective1)
    GL.MatrixMode(MatrixMode.Modelview) ' Select The Modelview Matrix
    GL.LoadIdentity() ' Reset The Matrix
    GL.Enable(EnableCap.DepthTest) ' This doesnt need to be here but.. If your using the Z buffer.. It dont hurt.

End Sub


Public Sub ViewOrtho()
    GL.MatrixMode(MatrixMode.Projection) 'Select Projection
    GL.LoadIdentity() ' Reset The Matrix
    GL.Ortho(0, GlControl1.Width, -GlControl1.Height, 0, 0.1, 100.0) ' Select Ortho Mode
    GL.MatrixMode(MatrixMode.Modelview) ' Select Modelview Matrix
    GL.LoadIdentity() ' Reset The Matrix
End Sub

8) Lastly, I tried to call them:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    ViewOrtho()
End Sub

The above results in no display, so any help would be greatly appreciated.

Even if you don’t know a full solution, any response wouldbe nice.

Answer 1

I have solved my own question :p I have created a wrapper class so that I can draw some primatives based on inputs which should allow me to draw many things: a circle, polygon, triangle, and text.

Private Sub GlControl1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GlControl1.Load
    GL.ClearColor(Color.Black)
    SetupViewport()
End Sub

Public Sub SetupViewport()
    Dim w As Integer = GlControl1.Width
    Dim h As Integer = GlControl1.Height
    GL.MatrixMode(MatrixMode.Projection)
    GL.LoadIdentity()
    GL.Ortho(0, w, 0, h, -1, 1)
    GL.Viewport(0, 0, w, h)
End Sub


Private Sub GlControl1_Resize(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles GlControl1.Resize
    SetupViewport()
    GlControl1.Invalidate()
End Sub


Private Sub GlControl1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles GlControl1.Paint
    GL.Clear(ClearBufferMask.ColorBufferBit)
    GL.Clear(ClearBufferMask.DepthBufferBit)

    'go through list and draw shapes
    Dim i As Integer = 0
    Try
        Do Until i = objectsettings.GetUpperBound(1) + 1
            Select Case objectsettings(1, i)
                Case "circle"
                    draw_circle(objectsettings(2, i), objectsettings(3, i), objectsettings(5, i), objectsettings(12, i))
                Case "polygon"
                    draw_polygon(objectsettings(2, i), objectsettings(3, i), objectsettings(6, i), objectsettings(7, i), objectsettings(4, i), objectsettings(12, i))
                Case "text"
                    draw_text(objectsettings(2, i), objectsettings(3, i), objectsettings(6, i), objectsettings(7, i), objectsettings(4, i), objectsettings(8, i), objectsettings(12, i))
                Case "triangle"
                    draw_triangle(objectsettings(2, i), objectsettings(3, i), objectsettings(4, i), objectsettings(9, i), objectsettings(10, i), objectsettings(11, i), objectsettings(12, i))
                Case Else
                    Exit Do
            End Select


            i = i + 1
        Loop
    Catch
    End Try



    GlControl1.SwapBuffers()

End Sub