hi,

i am new to opengl and understand the basics of it (thanks to NeHe).

i would like to draw line on an opengl canvas using vb.net. 

so far:
- i can get users mouse click (x,y coords) in mouse down method
- convert then to 3d coords using gluUnproject
- track users moving cursor (converted to 3d as well) and draw a line
between these to points

actual interaction with the program:
- program starts
- user clicks (nothing happens)
- user moves the mouse to a new location (nothing happen)
- user resizes the opengl form (during the resizing process if the
user put the cursor on the form the programs draws the line from the
first click to the current mouse position)

don't understand what is going wrong?

do i need some kind of redraw method, if so where & when would it be
called or do i need some kind of refreshing mechanism, refreshing my
drawing?

if there some tutorials out there regarding this topic do mention
them.

help appreciated.
pj

Do you have an Idle func? I guess you have a reshape func.  See if you
have anything missing.

Michael wrote:
> Do you have an Idle func? I guess you have a reshape func.  See if
you
> have anything missing.

What is an Idle func?

the following code is simply meant to draw a pixel where the user
clicks:

Actual interactions:
-user clicks (nothing happens)
-user resuzes the canvas (pixel appears at the clicked position)
-user resizes the canvas (pixel disappears)

any ideas?

do i need some kind of a redraw method? if so how do i use it and call
it?

=====================================================

Public Class Form1

Inherits System.Windows.Forms.Form

Public Class OurView

Inherits CsGL.OpenGL.OpenGLControl
'global variable declarations
'global x,y,z coords
Public Shared mposWldX As Double = 0
Public Shared mposWldY As Double = 0
Public Shared mposWldZ As Double = 0
'mouse positions
'save the 1st click
Public Shared mposWinX1 As Integer = 0
Public Shared mposWinY1 As Integer = 0
Public Shared mposWinZ1 As Integer = 0
'save the 2nd click
Public Shared mposWinX2 As Integer = 0
Public Shared mposWinY2 As Integer = 0
Public Shared mposWinZ2 As Integer = 0
'save the 1st world coords
Public Shared mposWldFirstX As Single = 0
Public Shared mposWldFirstY As Single = 0
Public Shared mposWldFirstZ As Single = 0
'bool for saving the 1st world coords
Public Shared check As Boolean = True
'bool so as to check user has started drawing
Shared startDrawing As Boolean = False

Protected Overrides Sub InitGLContext()
'// Enable Smooth Shading
GL.glShadeModel(Convert.ToUInt32(GLFlags.GL_SMOOTH))
'// Black Background
GL.glClearColor(0.0F, 0.0F, 0.0F, 0.5F)
'// Depth Buffer Setup
GL.glClearDepth(1.0F)
'// Enables Depth Testing
GL.glEnable(Convert.ToUInt32(GLFlags.GL_DEPTH_TEST))
'// The Type Of Depth Testing To Do
GL.glDepthFunc(Convert.ToUInt32(GLFlags.GL_LEQUAL))
'// Really Nice Perspective Calculations
GL.glHint(Convert.ToUInt32(GLFlags.GL_PERSPECTIVE_CORRECTION_HINT),
Convert.ToUInt32(GLFlags.GL_NICEST))
End Sub



Public Overloads Sub glDraw(ByVal _posX As Single, ByVal _posY As
Single, ByVal _posZ As Single)

'MsgBox("_posX: " + _posX.ToString + " _posY: " + _posY.ToString + "
_posZ: " + _posZ.ToString)
'// Clear The Screen And The Depth Buffer
GL.glClear(Convert.ToUInt32(GLFlags.GL_COLOR_BUFFER_BIT Or
GLFlags.GL_DEPTH_BUFFER_BIT))
'// Reset The Current Modelview Matrix
GL.glLoadIdentity()
'set point size
OpenGL.glPointSize(20)
'green color
GL.glColor3f(1.0F, 1.0F, 1.0F)
'// Draw A point
GL.glBegin(Convert.ToUInt32(GLFlags.GL_POINTS))
'''''''''
'// a point
GL.glVertex3f(_posX, _posY, _posZ)
'''''''''
GL.glEnd()
End Sub


Protected Overrides Sub OnSizeChanged(ByVal e As System.EventArgs)
MyBase.OnSizeChanged(e)
Dim S As Size = Me.Size

GL.glMatrixMode(Convert.ToUInt32(GLFlags.GL_PROJECTION))
GL.glLoadIdentity()
GL.gluPerspective(45.0, S.Width / S.Height, 0.1, 100.0)
GL.glMatrixMode(Convert.ToUInt32(GLFlags.GL_MODELVIEW))
GL.glLoadIdentity()
End Sub

Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As
System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown

'user has started drawing
startDrawing = True

mposWinX1 = e.X
mposWinY1 = e.Y

'pass x & y mouse coords to be converted to 3d x,y,z using
gluUnproject()
convert2dTo3d(mposWinX1, mposWinY1, mposWinZ1)

glDraw(CSng(mposWldX), CSng(mposWldY), CSng(mposWldZ))

End Sub


'converts windows x,y to 3d x,y,z
Private Function convert2dTo3d(ByVal _winX As Integer, ByVal _winY As
Integer, ByVal _winZ As Integer) As Array

'MsgBox("3d method got x: " + _winX.ToString + " y: " + _winY.ToString)

'declare viewport, modelview, projection
Dim viewport As Integer() = New Integer(4) {}
Dim modelview As Double() = New Double(16) {}
Dim projection As Double() = New Double(16) {}
Dim winX, winY, winZ As Integer

'??????
GL.glGetDoublev(Convert.ToUInt32(GLFlags.GL_MODELVIEW_MATRIX),
modelview)
GL.glGetDoublev(Convert.ToUInt32(GLFlags.GL_PROJECTION_MATRIX),
projection)
GL.glGetIntegerv(Convert.ToUInt32(GLFlags.GL_VIEWPORT), viewport)

'set the x,y,z values
winX = _winX
winY = viewport(3) - _winY
winZ = _winZ
'MsgBox("x:" + winX.ToString + " y: " + winY.ToString)
'GL.glReadPixels((winX, winY, 1, 1,
Convert.ToUInt32(GLFlags.GL_DEPTH_COMPONENT),
Convert.ToUInt32(GLFlags.GL_FLOAT), 0)

'actual convertion
GL.gluUnProject(winX, winY, winZ, modelview, projection, viewport,
mposWldX, mposWldY, mposWldZ)

'temp array to send 3d x,y,z
Dim tempArray As Double() = New Double(2) {mposWldX, mposWldY,
mposWldZ}
'MsgBox("3d method sending x: " + tempArray(0).ToString + " y: " +
tempArray(1).ToString + " z: " + tempArray(2).ToString)
Return (tempArray)

End Function
End Class

=====================================================