Question about TBGL_DrawFrame

For the past week I've been porting a simple Java program over to thinBasic. It's nothing impressive, it just draws an image on the screen. The pseudo code for the drawing routine looks much like the following.

Code:

---

For x = 1 To %winWidth
 
  For y = 1 To %winHeight
 
  Next
 
  TBGL_DrawFrame

Next

---

I've placed TBGL_DrawFrame between the two Next commands so that the User can see the image being drawn on the screen, however as it's being drawn it flickers quite badly. The ways that I've found to overcome this are to use glDrawBuffer(%GL_FRONT_AND_BACK) or use glDrawBuffer(%GL_FRONT) and glFlush().

Is there a TBGL way of overcoming the flickering without resorting to native OpenGL commands?

Hi Matthew,

always so pleasant to see you here :) Please, if you can, share the code and I can check for the possible root cause of flicker.
If you prefer to not share here at the moment, just send it at petrschreiber@thinbasic.com.


Petr

Hi Petr don't worry the program I'm writing isn't Top Secret, I'm happy to share. :-)

Prepare yourself for a lot of links. After reading this thread on the BASIC programming forum I was interested in finding out more about Voronoi diagrams. I ended up finding this Java program on Rosetta Code, so I thought I'd port it to different dialects of BASIC. So-far I've ported it to FreeBASIC and Basic4GL. I should add that both versions flickered just the same until I started using glDrawBuffer(%GL_FRONT_AND_BACK).

The program is a bit slow (and uncommented) at the moment but I hope in the future to make it a bit faster by using GBuffers and Oxygen.

Code:

---


Uses "TBGL"
#INCLUDE "%app_includepath%\thinbasic_gl.inc"

Randomize

Dim hWnd As DWord

%winWidth  = 640
%winHeight = 480
%winDepth  = 32
 
hWnd = TBGL_CreateWindowEx("Voronoi diagram", %winWidth, %winHeight, %winDepth, %TBGL_WS_WINDOWED | %TBGL_WS_DONTSIZE | %TBGL_WS_CLOSEBOX)
TBGL_ShowWindow

TBGL_RenderMatrix2D ( 0, %winHeight, %winWidth, 0) 
TBGL_BackColor 0, 0, 0, 0
' glDrawBuffer(%GL_FRONT_AND_BACK)
' glDrawBuffer(%GL_FRONT)

Long sites = 10
Long townX(sites), townY(sites)
Long colR(sites), colG(sites), colB(sites)
Long i, n, x, y
Long appRunning = %FALSE
             

For i = 1 To sites
  townX(i) = Rnd(0, %winWidth)
  townY(i) = Rnd(0, %winHeight)
  colR (i) = Rnd(0, 255)
  colG (i) = Rnd(0, 255)
  colB (i) = Rnd(0, 255)
Next


TBGL_ResetKeyState()

While TBGL_IsWindow(hWnd)

  TBGL_ClearFrame
       
  For x = 1 To %winWidth
 
    For y = 1 To %winHeight
     
      n = 1
     
      For i = 1 To sites
       
        If VoronoiDistance(townX(i), x, townY(i), y) < VoronoiDistance(townX(n), x, townY(n), y) Then
          n = i
        EndIf
       
      Next
     
    TBGL_BeginPoly(%GL_POINTS)
      TBGL_Color(colR(n), colG(n), colB(n))
      TBGL_Point(x, y)
    TBGL_EndPoly
   
    Next
       
  DoEvents
 
  If TBGL_GetWindowKeyOnce(hWnd, %VK_ESCAPE) Then Exit For
  TBGL_DrawFrame
  ' glFlush()
     
  Next
 
If appRunning = %FALSE Then Exit While
     
Wend

TBGL_DestroyWindow

Function VoronoiDistance(x1, x2, y1, y2 As Long) As Double
  Dim distance As Double
    distance = Sqr(((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2)))
  Return distance
End Function

---

not your demo matthew but the first example in http://forum.basicprogramming.org/in...ic,5127.0.html
it produced the same shape almost instantly. its 2D inside 3D so we can rotate it (uncomment line 40)
not optimized , i just filled Petr code about using oxygen for the math hard task and Gbuffers to store the arrays here http://www.thinbasic.com/community/s...2365#post92365
the most important lines is:
Dim oVertexA() At #VertexA As TBGL_TVECTOR3F
Dim oColorA() At #ColorA As TBGL_TRGB

since it connects the arrays oVertexA to arrays VertexA, it seems oVertexA dimensioned as necessary.
the arrays is linear but we project the 2D point in the above page to 1D like this:
ind = (yy-1)*640 + xx
oVertexA(ind).x = xx

Attachment 9414

Code:

---

Uses "TBGL", "math", "Oxygen"
 
Function TBMain()
  Local hWnd      As DWord
  Local FrameRate As Double
   
  ' -- Create and show window
  hWnd = TBGL_CreateWindowEx("Plotting 3D Data in an array using GBuffers- Calculate with Oxygen JIT ..Esc to quit", 600, 600, 32, %TBGL_WS_WINDOWED Or %TBGL_WS_CLOSEBOX)
  TBGL_ShowWindow
   
  TBGL_BackColor 255,255,255

  ' -- Create 3D points buffer
  DWord gbPoints = TBGL_GBufferCreate(%TBGL_POINTS, %TBGL_3D)
   
  Global Nb As DWord = 1000000
 
  ' -- Define data for it
  Global VertexA(Nb) As TBGL_TVECTOR3F ' single
  Global ColorA(Nb)  As TBGL_TRGB      ' Byte
 
  FillArrays()
 
  ' -- Create buffer dynamically linked to the arrays above
  TBGL_GBufferDefineFromArray(gbPoints, %TBGL_DYNAMIC, CountOf(VertexA), VertexA(1), ColorA(1))
 
  ' -- Resets status of all keys
  TBGL_ResetKeyState()
  'TBGL_PointSize 2
 
  ' -- Main loop
  While TBGL_IsWindow(hWnd)
  'init
    FrameRate = TBGL_GetFrameRate
   
    TBGL_ClearFrame
      TBGL_Camera(0, 0, 40, 0, 0, 0)
       
      ' -- Turn triangle
      'TBGL_Rotate GetTickCount/50, 0, 1, 0
      TBGL_Scale 0.045, 0.045, 1
      TBGL_Translate -320, -320
                                     
      ' -- Render it                             
      TBGL_GBufferRender(gbPoints) 
       
    TBGL_DrawFrame
 
    ' -- ESCAPE key to exit application
    If TBGL_GetWindowKeyState(hWnd, %VK_ESCAPE) Then Exit While
 
  Wend     
  ' -- Destroying the buffer is not necessary,
  ' -- the garbage collector will take care of it
 
  ' -- Destroy window
  TBGL_DestroyWindow
End Function 
 
Function FillArrays()
 
  String src = "
  basic
 
  ' -- Re-declare types
  Type TBGL_TRGB
    r As Byte
    g As Byte
    b As Byte
  End Type
 
  Type TBGL_TVECTOR3F
    x As Single
    y As Single
    z As Single
  End Type
 
 
  'RANDOMISER
  '==========
  '
  Dim seed As Long=0x12345678
  '
  Function Rnd() As Single  'this is from oxygen examples in thinbasic folder
    '
    Static As Single f, d=1/0x7fffffff
    mov eax,seed
    rol eax,7
    imul eax,eax,13
    mov seed,eax
    push eax
    fild DWord [esp]
    ADD esp,4
    fmul DWord d
    fstp DWord f
    Function=f
  End Function
   
  ' -- Link variables 
  Dim oVertexA() At #VertexA As TBGL_TVECTOR3F
  Dim oColorA() At #ColorA As TBGL_TRGB
Single g
Long i

Integer sq=640: Single s2 = sq/2 

#def points 240
Dim x(points) as single
Dim y(points) as single
dim kl(points) as TBGL_TRGB

For i = 1 To points
  x(i)=abs(Rnd()*sq): y(i)=abs(Rnd()*sq)
  g=127-127*(Abs(s2-x(i))/s2)+127-127*(Abs(s2-y(i))/s2)
  kl(i).r=255-x(i)/sq*255
  kl(i).g = g
  kl(i).b = y(i)/(sq*255)
Next
 

  Single a, b, q
  Long xx, yy, d , kkl, i
  For xx = 1 To sq
  For yy = 1 To sq
      d = 307201
      For i = 1 To points
        a=x(i)-xx: b=y(i)-yy
        q=a*a+b*b
        If q < d Then d = q: kkl = i
      Next i
      ind = (yy-1)*640 + xx
      oVertexA(ind).x = xx
      oVertexA(ind).y = yy
      oVertexA(ind).z = 0
      oColorA(ind).r = kl(kkl).r
      oColorA(ind).g = kl(kkl).g
      oColorA(ind).b = kl(kkl).b
      'oColorA(i).r = 255:oColorA(i).g=0: oColorA(i).b=0
      'pset xx,yy,kl(kkl)
  Next yy
Next xx
   
  terminate   
  "       
 
  ' -- Pass the source
  O2_Asmo src
 
  ' -- Check for errors
  If Len(o2_error) Then
    MsgBox 0, o2_error : Stop
  End If             
 
  ' -- Execute
  o2_exec
 
End Function

---

Very impressive. :-)

Matthew,

as I understand it, your original example basically needed something like single buffer, something to have image visible immediately. I... I am sorry, but I do not think single buffering should still exist in 21st century :D*
But of course, I want you to enable you to do what you need. So... what about thinking about the problem differentely? What about having a canvas under your control?

It is an approach I learned to use, and maybe you will like it too. For canvas, you can use memory bitmap. That is persistent. And then map it on quad.
And yes, one more tip. You don't need to define VoronoiDistance, thinBasic has it covered with optimized Dist function!:

Code:

---

Uses "TBGL"
 
Randomize
 
%winWidth  = 640
%winHeight = 480
%winDepth  = 32
 
DWord hWnd = TBGL_CreateWindowEx("Voronoi diagram", %winWidth, %winHeight, %winDepth, %TBGL_WS_WINDOWED | %TBGL_WS_DONTSIZE | %TBGL_WS_CLOSEBOX)
TBGL_ShowWindow
 
TBGL_RenderMatrix2D ( 0, %winHeight, %winWidth, 0) 
TBGL_BackColor 0, 0, 0, 0
         
Long sites = 10
Long townX(sites), townY(sites)
Long colR(sites), colG(sites), colB(sites)
Long i, n, x, y
       
For i = 1 To sites
  townX(i) = Rnd(0, %winWidth)
  townY(i) = Rnd(0, %winHeight)
  colR (i) = Rnd(0, 255)
  colG (i) = Rnd(0, 255)
  colB (i) = Rnd(0, 255)
Next       
 
TBGL_ResetKeyState()     

' -- Canvas built as black
String drawingCanvas = Repeat$(%winWidth*%winHeight, Chr$(0, 0, 0, 255))

' -- Now we overlay a easy to handle array over
Dim pixelOverlay(%winWidth, %winHeight) As TBGL_TRGBA At StrPtr(drawingCanvas)

Long xStep = 5 ' -- How much lines at time?
Long lastX = 1 ' -- Memory for x
 
While TBGL_IsWindow(hWnd)
 
  TBGL_ClearFrame

    For x = lastX To Min(lastX+xStep, %winWidth)
     
      For y = 1 To %winHeight     
        n = 1                     
        For i = 1 To sites           
          If Dist(townX(i), townY(i), x, y) < Dist(townX(n), townY(n), x, y) Then
            n = i
          EndIf                     
        Next

        ' -- Writing bitmap like a thinBasic boss       
        With pixelOverlay(x, y)
          .r = colR(n)
          .g = colG(n)
          .b = colB(n)
        End With 
     
      Next
     
      If TBGL_GetWindowKeyOnce(hWnd, %VK_ESCAPE) Then Exit While
      TBGL_MakeTexture drawingCanvas, %TBGL_DATA_RGBA, %winWidth, %winHeight, 1, %TBGL_TEX_NEAREST
    Next
    lastX = x         
           
    TBGL_PushState %TBGL_TEXTURING
      TBGL_BindTexture 1
      TBGL_BeginPoly %GL_QUADS
        TBGL_TexCoord2D 0, 0 : TBGL_Vertex        0, 0
        TBGL_TexCoord2D 1, 0 : TBGL_Vertex %winWidth, 0
        TBGL_TexCoord2D 1, 1 : TBGL_Vertex %winWidth, %winHeight
        TBGL_TexCoord2D 0, 1 : TBGL_Vertex        0, %winHeight
      TBGL_EndPoly
    TBGL_PopState
   
    If TBGL_GetWindowKeyOnce(hWnd, %VK_ESCAPE) Then Exit While
   
  TBGL_DrawFrame
     
Wend
 
TBGL_DestroyWindow

---

Of course, this example does not reach the performance of Primo's Oxy accelerated solution, as it uses pure parsing, but it could be further combined with oxygen to reach optimum performance.


Petr

* I will give a thought to enabling single buffering in TBGL

I still do a lot of my programming in Basic4GL which isn't too fast when it comes to creating Fractals and similar mathematical drawing so I usually just draw straight to the front buffer using glDrawBuffer(GL_FRONT) and glFlush() as it's a little faster than swapping buffers which I feel is a waste when nothing's actually moving on the screen.

Your method of drawing onto a Quad is something else I was thinking of doing in Basic4GL using glTexSubImage2D, I didn't even know that thinBasic had a Dist function built-in so thanks for that.

Why don't you like single-buffering? :-) I've always found it useful for getting quick results for some programs.

Hehe,

good question. Maybe I think that single buffer and GPU graphics don't go much together, as the main benefit -performance- is usually lost and/or you are using it for per pixel operations, while GPU graphics are shining most when working at vector level.

See this GPU-less example :)
(And guess what, Canvas can be used in double buffer mode too)

Code:

---

Uses "UI"
 
Randomize
 
%winWidth  = 640
%winHeight = 480
%winDepth  = 32
   
DWord hWnd = Canvas_Window("Voronoi diagram", 100, 100,%winWidth, %winHeight)
Canvas_Attach(hWnd, 0)
           
Long sites = 10
Long townX(sites), townY(sites)
Long colR(sites), colG(sites), colB(sites)
Long i, n, x, y
         
For i = 1 To sites
  townX(i) = Rnd(0, %winWidth)
  townY(i) = Rnd(0, %winHeight)
  colR (i) = Rnd(0, 255)
  colG (i) = Rnd(0, 255)
  colB (i) = Rnd(0, 255)
Next     
 
While IsWindow(hWnd)
 
    For x = 0 To %winWidth
       
      For y = 0 To %winHeight     
        n = 1                     
        For i = 1 To sites           
          If Dist(townX(i), townY(i), x, y) < Dist(townX(n), townY(n), x, y) Then
            n = i
          EndIf                   
        Next
 
        Canvas_SetPixel(x, y, Rgb(colR(n), colG(n), colB(n)))
       
      Next
       
      If Asc(Canvas_Inkey) = 27 Then Exit While
     
    Next
       
    If Asc(Canvas_Inkey) = 27 Then Exit While
       
Wend

---

Petr

Please do not use infinite loops otherwise script will continue to run (as a process) even if the main window is closed.

Correct loop would be something like:

Code:

---

While IsWindow(hWnd)
...
Wend

---

In this way, when the hWnd window will be closed the script will stop execution.

Ciao
Eros

Fixed, nice catch :)