A challenge porting from FreeBasic (and originally from C)

[sblank]

I worked on porting my FreeBasic OpenGL program over the weekend and became stuck on the following two lines in the chaptrack function:

glMultMatrixf @aff(0)
glGetFloatv GL_TEXTURE_MATRIX, @aff(0)

The aff() matrix is the affine matrix used in the rotations of the 3D figure. I use the GL_TEXTURE_MATRIX because it is handy and not being used for any other purpose

Anyway, I'm using a pointer to multiply the aff() matrix by the current transformation/rotation matrix and then storing the newly transformed matrix in GL_TEXTURE_MATRIX. Again, using pointers...

I am not certain how to do this using TBGL or raw OpenGL in thinBasic... I tried using varptr but obviously did not know what I was doing

Thanks for any "pointers" you might have,

Stan

[Petr Schreiber]

Hi Stan,

no need to struggle with pointers, as the declaration is made to get the array by reference. So for the two lines, the TB code would look like:

glMultMatrixf(matrix)
glGetFloatv(%GL_TEXTURE_MATRIX, matrix)

Petr

[sblank]

Fantastic... thanks for the "pointer"

Seriously, I'll give this a try. ByRef makes sense.

Cheers,

Stan

Hi Stan,

no need to struggle with pointers, as the declaration is made to get the array by reference. So for the two lines, the TB code would look like:

glMultMatrixf(matrix)
glGetFloatv(%GL_TEXTURE_MATRIX, matrix)

Petr

[Petr Schreiber]

I prefer the byref approach over pointers (less typing, same effect), that's why headers are translated this way.

If you are unsure about parameters, you can always check the headers in the ThinBASIC/Inc directory or ask here of course!

We had a few iterations of the headers until we found current state, originally there were the pointers everywhere, but I think the current way is more user friendly (once you know BYREF is there ).


Petr

[sblank]

I agree... ByRef is much simpler than trying to use pointers (for me, anyway). Sending the matrix name (ByRef) worked!

Another question:

What is the TBGL equivalent of the glutIdle() function? Is that your "while TBGL_IsWindow" function?

I use glutIdle() in the program I'm trying to port... just curious.

Thank,

Stan

I prefer the byref approach over pointers (less typing, same effect), that's why headers are translated this way.

If you are unsure about parameters, you can always check the headers in the ThinBASIC/Inc directory or ask here of course!

We had a few iterations of the headers until we found current state, originally there were the pointers everywhere, but I think the current way is more user friendly (once you know BYREF is there ).


Petr

[Petr Schreiber]

Hi Stan,

it's up to you how you structure code in TBGL, the endless loop is just one approach possible.

The another could be to use the periodic function and base the organization on that.

Here minimal example, hWnd and FrameRate are passed to idle and input functions just in case you would like to use it, but it is not necessary of course.

Uses "TBGL"    

Global angle As Double

Function TBMain()
  Local hWnd      As DWord
  Local FrameRate As Double
  
  ' -- Create and show window
  hWnd = TBGL_CreateWindowEx("TBGL script - press ESC to quit", 640, 480, 32, %TBGL_WS_WINDOWED Or %TBGL_WS_CLOSEBOX) 
  TBGL_ShowWindow 

  ' -- Initialize lighting
  TBGL_UseLighting(%TRUE)
  TBGL_UseLightSource(%GL_LIGHT0, %TRUE)

  TBGL_SetLightParameter(%GL_LIGHT0, %TBGL_LIGHT_POSITION, 15, 10, 15, 1)

  ' -- Resets status of all keys 
  TBGL_ResetKeyState()

  TBGL_BindPeriodicFunction( hWnd, "funRender", 10 )
  TBGL_ProcessPeriodicFunction(hWnd)

  TBGL_DestroyWindow
End Function 

' -- Do any calculations here
Function funIdle( hWnd As DWord, frameRate As Double )
                               
  angle += 90/FrameRate
  
End Function

' -- Handle input here
Function funInput( hWnd As DWord, frameRate As Double )

  If TBGL_GetWindowKeyState(hWnd, %VK_ESCAPE) Then 
    TBGL_UnBindPeriodicFunction(hWnd)
    Exit Function
  End If

End Function

Function funRender()

  Dim hWnd As DWord = TBGL_CallingWindow
  Dim FrameRate As Double
  
  frameRate = TBGL_GetFrameRate    
    
  ' -- Process input
  funIdle( hWnd, FrameRate)
  
  ' -- Process calculations
  funInput( hWnd, FrameRate )
  
  FrameRate = TBGL_GetFrameRate

  TBGL_ClearFrame 
    TBGL_Camera(15, 15, 15, 0, 0, 0)
    
    TBGL_Rotate(angle,0,1,0)
    TBGL_Color(255, 128, 0)
    TBGL_Box(1, 1, 1)

  TBGL_DrawFrame   

End Function

Petr

[sblank]

Hi Petr,

Very nice! This should help immensely...

When I finish the translation, I'll have to list you as a co-author

Thank you very much for the tip... and for the elegant program example!

Stan

Hi Stan,

it's up to you how you structure code in TBGL, the endless loop is just one approach possible.

The another could be to use the periodic function and base the organization on that.

Here minimal example, hWnd and FrameRate are passed to idle and input functions just in case you would like to use it, but it is not necessary of course.

Uses "TBGL"    

Global angle As Double

Function TBMain()
  Local hWnd      As DWord
  Local FrameRate As Double
  
  ' -- Create and show window
  hWnd = TBGL_CreateWindowEx("TBGL script - press ESC to quit", 640, 480, 32, %TBGL_WS_WINDOWED Or %TBGL_WS_CLOSEBOX) 
  TBGL_ShowWindow 

  ' -- Initialize lighting
  TBGL_UseLighting(%TRUE)
  TBGL_UseLightSource(%GL_LIGHT0, %TRUE)

  TBGL_SetLightParameter(%GL_LIGHT0, %TBGL_LIGHT_POSITION, 15, 10, 15, 1)

  ' -- Resets status of all keys 
  TBGL_ResetKeyState()

  TBGL_BindPeriodicFunction( hWnd, "funRender", 10 )
  TBGL_ProcessPeriodicFunction(hWnd)

  TBGL_DestroyWindow
End Function 

' -- Do any calculations here
Function funIdle( hWnd As DWord, frameRate As Double )
                               
  angle += 90/FrameRate
  
End Function

' -- Handle input here
Function funInput( hWnd As DWord, frameRate As Double )

  If TBGL_GetWindowKeyState(hWnd, %VK_ESCAPE) Then 
    TBGL_UnBindPeriodicFunction(hWnd)
    Exit Function
  End If

End Function

Function funRender()

  Dim hWnd As DWord = TBGL_CallingWindow
  Dim FrameRate As Double
  
  frameRate = TBGL_GetFrameRate    
    
  ' -- Process input
  funIdle( hWnd, FrameRate)
  
  ' -- Process calculations
  funInput( hWnd, FrameRate )
  
  FrameRate = TBGL_GetFrameRate

  TBGL_ClearFrame 
    TBGL_Camera(15, 15, 15, 0, 0, 0)
    
    TBGL_Rotate(angle,0,1,0)
    TBGL_Color(255, 128, 0)
    TBGL_Box(1, 1, 1)

  TBGL_DrawFrame   

End Function

Petr