Triple buffering:
1. With double buffering one buffer is being displayed and the second is being drawn to off-screen.
Then (with V-sync enabled) the computer just sits and waits until the frame is completely displayed and switches the buffers so the second one is displayed and the first one becomes offscreen. While the computer is waiting for the buffer it can do many other usefull things. Basically, it is underloaded and your frame rate depends on your monitor refresh rate. If the monitor refresh rate is 100Hz, you may get 100, 75, 50, 33, 25 fps. stable 33 to 25 fps is very playable.
2. If you turn off the V-sync, the off-screen buffer can be substituted in mid-frame, causing some ugly visual "tearing" effects. Of course the computer is now 100% loaded. If it can draw 300 frames per second and monitor can display only 75, it will still do that.
Your peak indicated frame rate will be higher then in case 1. Even higher then the monitor refresh rate. But since the PC is overloaded doing unnecessary work, the other tasks will get less attention then needed - communications, sound, ballistics, ets. So your framerate, FM, comms, everything will be less consistent. Your worst case will be worse then case 1.. You may have more trouble aiming with the higher frame rate because it is much easier to do it with a stable 30fps or 25 fps then when it changes from 100 to 30 fps.
Consistent 30 fps means that the image on the screen is delayed by 0.033 sec (0.04 sec for 25fps). Just like extra 33-40 ms added to the ping time. If it's stable, you subconciously adjust for that with your lead when aiming. If the frame rate jumps 100-20, the delay changes from 0.01 to 0.05. You may not notice it, but your gunnery will suffer and you will get tired faster. You will get eyestrain and headache sooner.
Also, your video card and CPU get hotter and your electric bill goes up.
3. Triple buffering introduces another off-screen buffer, so when the 2nd buffer is done, it starts writing the 3rd. So you do not change the frame mid-screen and avoid "tearing" effects even with V-sync enabled. The computer is still overloaded - you could switch several times between off-screen buffers while one frame is displayed, so most of the work is lost. All the negative effects of the case 2. still exist except for "tearing" image.
There is a price for that: another buffer takes 1280x1024x4 = 5,242,880 bytes. Over 5 megs out of 32 megs a modern card has. So if there is not enough memory left for textures, the AGP texturing will have to be used, so the main memory bus will be overloaded and the whole system suffer. So your best case will still never be better then your monitor refresh rate, but worst case may be even worse - 15 frames instead of 25-30. Also the packets will be received less consistently, so more warps, sound problems, control latency, etc.
Why triple buffering is used - it is a great marketing trick. The company can report that Quake at 800x600 (texture memory not an issue at low res) reports 230 frames per second! No matter that the monitor cannot display more then 75-100, regardless how many are drawn.
Forget tripple buffering. It is better to fly AH with 30 fps when your PC is underloaded or try for higher resolution, then suffer the side effects.
Z-buffer. If you do not need it (3-D glasses?), do not use it. It most likely causes some performance loss, otherwise HTC would not make it optional.
miko
[This message has been edited by miko2d (edited 09-21-2000).]
