[SOLVED] Why does rendering in thread doesn't work?

[Pascal]

I am going to put my gl rendering into a thread but i can't get it gooing.
If i put the rendering in a OnTimer-Event it works but if i call the
same OnTimer-Event in my thread it doesn't work.

OnTimer-event:

Code: Pascal  [Select][+][-]

1. procedure TForm1.Timer1Timer(Sender: TObject);
2. var
3.   Speed: Double;
4. begin
5.   glEnable(GL_DEPTH_TEST);
6.   glDepthFunc(GL_GEQUAL);
7.   glEnable(GL_TEXTURE_2D);
8.   glClearDepth(0);
9.  
10.   glClearColor(0.0, 0.0, 0.0, 0.0);
11.   glClear(GL_DEPTH_BUFFER_BIT or GL_COLOR_BUFFER_BIT);
12.   glMatrixMode(GL_PROJECTION);
13.   glLoadIdentity();
14.   //glViewport(0,0, pWidth, pHeight);
15.   glOrtho(0, fProject.Width, fProject.Height, 0, -256, 256);
16.   //gluPerspective(45.0, width / height, 0.1, 100.0);
17.   glMatrixMode(GL_MODELVIEW);
18.   glLoadIdentity();
19.   glEnable(GL_BLEND);
20.   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
21.  
22.   fSlide.Render(0);
23.  
24.   OpenGLControl1.SwapBuffers;
25. end;

Thread:

Code: Pascal  [Select][+][-]

1.   TPreview = class(TThread)
2.   private
3.     fProc: TNotifyEvent;
4.   protected
5.     procedure Execute; override;
6.   public
7.     constructor Create(pProc: TNotifyEvent);
8.   end;
9.   .
10.   .
11.   .
12. implementation
13.  
14. procedure TPreview.Execute;
15. begin
16.   while not Terminated do begin
17.     fProc(nil);
18.     Sleep(40);
19.   end;
20. end;
21.  
22. constructor TPreview.Create(pProc: TNotifyEvent);
23. begin
24.   inherited Create(true);
25.   fProc := pProc;
26. end;
27.  

[Cyrax]

You can't call any component method(s) that interacts with LCL (paint etc), in threads. Only main thread can call these methods.

[Pascal]

I know, but OpenGLContext doesn't do any painting just setting up the viewport and calling OnPaint which isn't set up in my case.
So it should work.

[Thaddy]

The rendering in the thread is not an issue, provided you protect the rendering code with a critical section.
But you need to call OpenGLControl1.SwapBuffers; in the context of the main thread. Not IN the thread. Or Syncronize(SwapBuffers), that's also possible.
The latter is more or less the same, but easier with your code and does not need a critical section, although I would recommend it anyway.

[Pascal]

Thaddy, thanks for the tip.

Unfortunately that doesn't make any difference 

Code: Pascal  [Select][+][-]

1. type
2.   TSimple = procedure of object;
3.  
4.   TPreview = class(TThread)
5.   private
6.     fControl: TOpenGLControl;
7.     fProc: TNotifyEvent;
8.     fInit: TSimple;
9.     procedure SwapBuffers;
10.   protected
11.     procedure Execute; override;
12.   public
13.     constructor Create(pInit: TSimple; pProc: TNotifyEvent; pControl: TOpenGLControl);
14.   end;
15.  
16.  
17. implementaion
18.  
19. procedure TPreview.SwapBuffers;
20. begin
21.   fControl.SwapBuffers;
22. end;
23.  
24. procedure TPreview.Execute;
25. var
26.   t: QWord;
27. begin
28.   fInit;
29.   while not Terminated do begin
30.     t := GetTickCount64;
31.     fProc(nil);
32.     if not Terminated then begin
33.       //Synchronize(@SwapBuffers);
34.       t := 40 - (GetTickCount64 - t);
35.       if t > 0 then Sleep(t);
36.     end;
37.   end;
38. end;
39.  
40. constructor TPreview.Create(pInit: TSimple; pProc: TNotifyEvent;
41.   pControl: TOpenGLControl);
42. begin
43.   inherited Create(true);
44.   fControl := pControl;
45.   fInit := pInit;
46.   fProc := pProc;
47. end;

[Thaddy]

What I was hinting at is the following:
You do the full rendering in the thread, on the current off-line buffer. Then call synchronize(swapbuffers). You are doing the painting somewhere else.

[Pascal]

The painting is done in the OnTimerEvent (which is called by the thread (Testcase)):

Code: Pascal  [Select][+][-]

1. procedure TForm1.Timer1Timer(Sender: TObject);
2. var
3.   Speed: Double;
4. begin
5.   OpenGLControl1.MakeCurrent;
6.   glEnable(GL_DEPTH_TEST);
7.   glDepthFunc(GL_GEQUAL);
8.   glEnable(GL_TEXTURE_2D);
9.   glClearDepth(0);
10.  
11.   glClearColor(1.0, 0.0, 0.0, 0.0);
12.   glClear(GL_DEPTH_BUFFER_BIT or GL_COLOR_BUFFER_BIT);
13.   glMatrixMode(GL_PROJECTION);
14.   glLoadIdentity();
15.   glViewport(0,0, OpenGLControl1.Width, OpenGLControl1.Height);
16.   glOrtho(0, fProject.Width, fProject.Height, 0, -256, 256);
17.   //gluPerspective(45.0, width / height, 0.1, 100.0);
18.   glMatrixMode(GL_MODELVIEW);
19.   glLoadIdentity();
20.   glEnable(GL_BLEND);
21.   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
22.   fSlide.Render(0);
23.   OpenGLControl1.SwapBuffers;
24. end;
25.  

Slide.Renderer:

Code: Pascal  [Select][+][-]

1. procedure TEPSlide.Render(pTime: Int64);
2. var
3.   o: TEPSlideObject;
4.   z: GLfloat;
5. begin
6.   z := 128;
7.   for o in fObjects do begin
8.     o.Render(pTime, z);
9.     z := z - 1
10.   end;
11. end;
12.  

Picture Renderer: (Slide contains on TEPPicture)

Code: Pascal  [Select][+][-]

1. procedure TEPPicture.Render(pTime: Int64; pZ: GLfloat);
2. begin
3.   glBindTexture(GL_TEXTURE_2D, FTexture);
4.   glBegin(GL_QUADS);
5.     glTexCoord2f(0,0); glVertex3f(FLeft,          FTop + FHeight, pZ);
6.     glTexCoord2f(1,0); glVertex3f(FLeft + FWidth, FTop + FHeight, pZ);
7.     glTexCoord2f(1,1); glVertex3f(FLeft + FWidth, FTop,           pZ);
8.     glTexCoord2f(0,1); glVertex3f(FLeft,          FTop,           pZ);
9.   glEnd;
10.  
11.   glColor4f(1.0, 1.0, 1.0, 1.0);
12. end;
13.  

So no magic here. It works in a timer but not in a thread.

[Pascal]

I  have an old delphi prototype where i did rendering in a thread. There everything is done in the thread
(including creating context). This prog uses dglOpenGL.pas.

Maybe i should use dglOpenGL instead of OpenGLContext and GL.

[Pascal]

Okay. Using dglOpenGL works as expected.
Maybe this is due to the context beeing created in the main thread.