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Newcomers DBPro Corner / What exactly is the backbuffer?

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Mystery Coffee Drinker
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Posted: 23rd Jan 2005 23:43
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answers on a postcard (or on the forums if you can't find a postcard)
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Cryptoman
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Posted: 24th Jan 2005 02:23
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The backbuffer is where things are supposed to be drawn before the sync. Then when you sync the backbuffer becomes the video you see on your monitor and the video you was viewing becomes the backbuffer. Its supposed to be used so you can't see the drawing take place.

And for most new video drivers it is only used correctly in FullScreen Exclusive mode unless you have a option to Wait For Vertical Sync in your drivers somewhere.


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Phaelax
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Posted: 24th Jan 2005 02:57
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It lets you do nifty effects

"eureka" - Archimedes
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Mystery Coffee Drinker
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Posted: 24th Jan 2005 22:43 Edited at: 25th Jan 2005 22:51
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Thanks for the responces

onwards from this, does anyone know the structure of the backbuffer ?
I know there are commands to find the height, pitch and depth, and I would assume that these numbers are held somewhere in the header of the backbuffer. as an example, I have a screen set to 1024x768x32, what would the backbuffer header look like, or better still, how could I find out for myself ?

[edit]
ok, there may be 12 bytes, but they don't seem to be at the beginning!
[/edit]

M.C.D
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Mystery Coffee Drinker
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Posted: 24th Jan 2005 23:40
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OK, I found from another post, that there is 12 bytes (3 DWORDS) for Width, Height & Depth. is it safe to assume that a 32bit screen depth will produce RGB Values as DWORDS, and if so, could they be read sequentially ? (across or down first?)

M.C.D
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Cryptoman
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Posted: 25th Jan 2005 01:44
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If I remember from 1983 apple was a funky math problem*7 to get the next line of screen, but I am sure the PC is still the same, once the first line bytes is up then you are on the next line. I know that not all GPUs read the video memory like that, but the drivers should hide the garbage.


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Mystery Coffee Drinker
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Posted: 25th Jan 2005 17:23
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do 3d objects get drawn to the backbuffer, if they don't by default, is there a way to force it ?

M.C.D
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