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View Full Version : Strange glitches when rotating and strafeing



trier
05-21-2004, 06:25 AM
Strange glicthes appears when i rotate and strafe my camera, its like gl updates the screen while displaying it, though i use double buffering?? when i only strafe(moveing sideways) everything seems normal. Any suggentions

Thanks in advance Trier

05-22-2004, 01:09 AM
Uh ? Can you post a screenshot ?

Maybe you update the front buffer when rotating the camera ?

If the problem is that the rendering is chopped by horizontal lines, the problem is that you don't use vertical synchronization (vsync). When the CRT monitor draws an images, it is done line by line from the top. If the rendering is updated in the middle, you basically see the older image at the top and the newer image at the bottom, separated by a horizontal line.
Vsync garanties to update the image only when the electron beam has finished an image and is ready to start a new one. You may be able to tests that quickly with the drivers control panel, sometimes there is a switch for default vertical sync.

Under windows, you can control that with the following extension (1 for vsync an 0 for no sync) see :
http://oss.sgi.com/projects/ogl-sample/registry/EXT/wgl_swap_control.txt

Of course, your framereate will decrease to be an 'under multiple' (the correct term in english ?) of your screen refresh rate . For 100hz, you can have such fps : 100,50,33,25,20, etc.