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Dom_152

Alpha blending

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I was reading an article about the Final Fantasy XIII demo and how it would work on the Xbox 360 found here and it mentions how the alpha blending effects used in certain sequences are a source of frame rate drops on the PS3. It then goes on to say that, thanks to 10mb of eDRAM connected to the GPU, this won't be so much of a problem on the 360. My question is why are alpha blending effects so costly in terms of performance and how does the 10mb of eDRAM help alleviate this? My only thought was that in order to do alpha blending the full resolution frame buffer needs to be in the video memory so the GPU has access to it and that having the frame stored in directly connected memory rather than general system memory connected via buses would help speed up this process. Is this correct or am I barking up the wrong tree here?

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Original post by Dom_152
My only thought was that in order to do alpha blending the full resolution frame buffer needs to be in the video memory so the GPU has access to it and that having the frame stored in directly connected memory rather than general system memory connected via buses would help speed up this process.


that would be the obvious assumption to come to. although, they must be doing a absolute metric s**tonne of alpha blending to cause a noticable frame rate drop, using a half sized render target for particles is one common way to speed things up (see Black on the PS2 for an example)

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