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Craazer

Reading surface is sooo slow.

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HI Why is that when i read my back buffer things get wery slow? Even when the back buffer is in VRAM, or thats where it its as default? Maybe this is a queston why combuters load slover than save, it sure seems to be like that? However is there any way to increase the speed?

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You are NOT supposed to read the buffer. Period.

On most graphics cards, reading speeds are TERRIBLE - way below AGP possible speeds (and I mean WAY). In fact you are NOT able to make a nice movie.

AND - by reading the back buffer you force a BRUTAL FULL STALL on the card.

Work around it - do NOT read the buffer if possible by any means.


Regards

Thomas Tomiczek
THONA Consulting Ltd.
(Microsoft MVP C#/.NET)

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quote:
Original post by thona
You are NOT supposed to read the buffer. Period.

On most graphics cards, reading speeds are TERRIBLE - way below AGP possible speeds (and I mean WAY). In fact you are NOT able to make a nice movie.

AND - by reading the back buffer you force a BRUTAL FULL STALL on the card.

Work around it - do NOT read the buffer if possible by any means.


Regards

Thomas Tomiczek
THONA Consulting Ltd.
(Microsoft MVP C#/.NET)


I know I know i was just hoping there would be shometing to do...
I need to read back buffer becose alpha plending.

Well thanks anyway.

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Why do you need to read it for alpha blending? This can be done on the card - totally. it is the AGP transfer that is slow :-)

Put your logic into a shader.


Regards

Thomas Tomiczek
THONA Consulting Ltd.
(Microsoft MVP C#/.NET)

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If you really need to read the buffer what you need to do is create a buffer in system memory and use that to render to and read from and then at the end of each frame copy it to the back buffer on the card.

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