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efficient main loop with opengl
https://delphigl.com/forum/viewtopic.php?f=19&t=8391		 Seite 1 von 1
Autor:  noeska [ So Mai 10, 2009 16:08 ]
Betreff des Beitrags:  efficient main loop with opengl
What is the best way to write a main loop for an api based opengl application?

In my current construction i get yerky results. (like it is frozen a bit every x seconds) Even though cpu usage stays below 10%.

Here is my main loop:

Code:
  1.  
  2. while not finished do
  3.   begin
  4.  
  5.     if (PeekMessage(msg, 0, 0, 0, PM_REMOVE)) then // Check if there is a message for this window
  6.     begin
  7.       if (msg.message = WM_QUIT) then     // If WM_QUIT message received then we are done
  8.         finished := True
  9.       else
  10.       begin                               // Else translate and dispatch the message to this window
  11.          TranslateMessage(msg);
  12.           DispatchMessage(msg);
  13.         Sleep(1);
  14.       end;
  15.     end else
  16.     begin
  17.       Inc(FPSCount);                      // Increment FPS Counter
  18.  
  19.       LastTime :=ElapsedTime;
  20.       ElapsedTime :=GetTickCount() - DemoStart;     // Calculate Elapsed Time
  21.       ElapsedTime :=(LastTime + ElapsedTime) DIV 2;
  22.  
  23.       if getfeedback = false then drawglscene; //here my scene is rendered
  24.  
  25.       sleep(1);
  26.  
  27.       if (keys[VK_ESCAPE]) then           // If user pressed ESC then set finised TRUE
  28.         finished := True
  29.       else
  30.       begin
  31.           fwdVel:=0;
  32.           yaw:=0;
  33.           pitch:=0;
  34.           if keys[VK_UP] then fwdVel:=0.2;
  35.           if keys[VK_DOWN] then fwdVel:=-0.2;
  36.           if keys[VK_LEFT] then yaw:=0.8;
  37.           if keys[VK_RIGHT] then yaw:=-0.8;
  38.           if keys[VK_PRIOR] then pitch:=0.8;  // page up
  39.           if keys[VK_NEXT]then pitch:=-0.8; // page down
  40.           if keys[VK_SPACE] then resetcamera:=true;
  41.       end;
  42.     end;
  43.   end;
  44.  


Should i ditch my main loop and do a total rewrite? And if so what would be the best way? Rendering from a thread? Rendering on idle (if that is detecteable from api only, i know it works with the forms template).

Thanks for your anwers in advance.
Autor:  Markus [ So Mai 10, 2009 17:05 ]
Betreff des Beitrags: 
What's the purpose of Sleep(1)? The call may take longer than 1ms, sometimes up to 16ms. That could be the cause of your lags.
Autor:  noeska [ So Mai 10, 2009 21:06 ]
Betreff des Beitrags: 
Removing the both sleep(1) does not make an improvement.

E.g. i get about 30 to 50 fps with waitforvblanc on. With waitforvblanc off i get about 70 fps.
Now with a very old build of my engine (pre version control, so where have i backed up those source files) i get
about 58 fps with waitforvblanc (that is quit nice since my lcd has a refresh rate of 60 (m)hz . And with waitforvblanc of i get about 170 fps. The realy strange thing is that the old one should have been slower as it does xml parsing each frame :twisted: .

Anyway i must have done something stupid. :oops: I just have to find what the cause is.

But tips on building a stable opengl environment are welcome.
E.g. how do i use the idle time?
Autor:  TAK2004 [ So Mai 10, 2009 21:47 ]
Betreff des Beitrags: 
Ich würde definitiv das PeekMessage in ein while packen, da sonnst nur eine Message pro frame abgearbeitet wird und weitere dann auflaufen.
Du berechnest die durchschnittliche Zeit pro Frame aber nutzt diese bei den Tastenevents weiter unten nicht und die berechnung der Zeit gefällt mir nicht.
Ich würde wie schon öfter im Forum gezeigt wurde das Delta auf minimum und Maximum Werte beschränken.
Das Problem könnte auftreten, wenn du ein FPS drop oder peek hast und somit die Variable ElapsedTime einen sinnfreien Mittelwert erhält(der noch auf die nächsten Frames Auswirkung hat).
Autor:  noeska [ So Mai 10, 2009 22:18 ]
Betreff des Beitrags: 
Placing the PeekMessage in a while did some good things. The engines seems to be more responsive. Makes sense given your explanation. Maybe i should loose the finished variable and make the PeekMessage the main while.
So next i should redesign the fps calculation.
What do you mean by i should use the average time on the key events?
Autor:  TAK2004 [ Mo Mai 11, 2009 03:36 ]
Betreff des Beitrags: 
Code:
  1. if keys[VK_UP] then fwdVel:=0.2*ElapsedTime;
  2. if keys[VK_DOWN] then fwdVel:=-0.2*ElapsedTime;
  3. if keys[VK_LEFT] then yaw:=0.8*ElapsedTime;
  4. if keys[VK_RIGHT] then yaw:=-0.8*ElapsedTime;
  5. if keys[VK_PRIOR] then pitch:=0.8*ElapsedTime; // page up
  6. if keys[VK_NEXT]then pitch:=-0.8*ElapsedTime; // page down
Autor:  Philip [ Mo Mai 11, 2009 22:22 ]
Betreff des Beitrags: 
Maybe you find this usefull:
http://dewitters.koonsolo.com/gameloop.html
Autor:  noeska [ Do Mai 21, 2009 18:48 ]
Betreff des Beitrags: 
:oops: never do xml parsing from a file streamed from within a vfs within the renderloop.
As when a collision occured i checked if an event was tied to the object the player collided with. That part is over 5 years old, what was i thinking back then. :shock:
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