Broekkie bracht ons een interessant linkje naar deze thread op het Beyond3D message board, over FSAA implementatie van Gigapixel. Gigapixel claimt dat het full scene anti-aliasing doet zonder performance penalty. Dat is uiteraard vreemd aangezien FSAA rekentijd vereist en dat moet ergens vandaan komen. Hier heb je een hap uit de eerste posting van deze thread:
So in short for FSAA you need to sample more data (they admit that they use a multisample approach, so nothing special tricky)... this data has to come from somewhere. Hoping for massive cache re-use is one thing but we all know that there is no guarantee for that. And then even if you have the data you need you still need the extra hardware to process all those sub-samples. I mean if they claim free, no hit when turning on this "must" mean that the silicon they use when not doing FSAA is shut down, not used, lost, a waste ? I mean they need some parts of their pipeline 4 times, does it make sense to just throw that silicon away when you disable FSAA ? Like 3dfx said in the past :"When there is no hit when going to 32 bit color then your 16 bit implementation sucks."
Can't we just say that when GP does free, no hit FSAA that their non FSAA implementation "sucks" ? This of course makes the whole PR sound very different. [break] Vervolgens komen er een aantal interessante reacties van Gary Tarolli en Scott Sellers (beide van 3dfx): [/break] ...the question you raise in terms of texture bandwidth really comes down to the issue of AA implementation. This is the super-sampling vs. multi-sampling issue. Everyone has different definitions of which-is-which, but suffice is to say that one of the approaches actually does a unique texture lookup per sub-sample, but the other approach does one texture lookup for all of the sub-pixels. The latter is what is done in the GP architecture. While it sounds like it could be a noticeable visual quality difference, it has been done at SGI for many generations and we don't see a lot of people complaining about their visual quality... In fact, I would say that the majority of professional AA solutions out there only do one texture lookup (well, to be more precise, perform the number of texture lookups equal to the number of textures being applied the the poly) per pixel, as opposed to the much more expensive approach of one texture lookup per subsample...
Fiets voor het complete verhaaltje richting het Beyond3D forum.
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