Uttar
01-27-03, 01:58 PM
EDIT: I did a mistake, and GFFX 4x images *are* 4x - the problem is that they're ordered and that, at the area I looked at, it looked a lot more like 3x. But I can nearly guarantee now that it's 4x.
However, the 2x problem remains.
Hey,
I'm ONLY going to base myself on Anand excellent AA comparaison screenshots. Thanks a lot for taking these, BTW, Anand!
I'm mirroring the images because Anand's server is still very busy as I write this.
http://www.notforidiots.com/Images
Okay, so look at the first image:
http://www.notforidiots.com/images/off.jpg
And compare it with:
http://www.notforidiots.com/images/2x-aa-aggressive.jpg
The first is an aliased result. The second is a 2X Antialiased result on a nVidia card.
Look closely and you'll see there IS a difference: the triangles seem *smaller* with 2x AA. Why?
Well, actually, some parts are also bigger. But I'll explain why later, for now only worry about the smaller parts ( such as the bottom-right of one of the left triangle )
Well, there are more very dark pixels. But... once again, why?
Well, let's look at ATI's 2x AA now, shall we?
http://www.notforidiots.com/images/2x-aa.jpg
Now, as you see, it looks a lot smoother. But let's compre it with nVidia 2X AA ( once again, it's here (http://www.notforidiots.com/images/2x-aa-aggressive.jpg) )
Now, look at the pixels which are not filled in nVidia's 2X AA, and which are filled when there is aliasing ( here (http://www.notforidiots.com/images/off.jpg) for the aliased image again )
Try to memorize ( or use multitasking to see several images at the same time, whatever ) which spots are not filled and were without 2x AA.
Now, look again at the ATI 2x AA image ( here (http://www.notforidiots.com/images/2x-aa.jpg) )
Look at the spots that I said you to remember. Guess what? Well, they're filled on the 2x AA screenshot, but they more dark than the remaining of the triangle. And what does that tell us?
That those are the pixels that should have only one of their two subpixels filled with that triangle.
Now, as I said before , some pixels are also filled on nVidia 2x and not when there's no AA. But if you look at the ATI 2x mode, it looks there that those pixels are only filled by the triangle in 1/2 of the subpixels.
So... that means AA IS happening ( there's the performance hit ) , but the two subpixel buffers are not merged. Sometimes that means a part looks bigger, sometimes it looks smaller. But in reality, only ONE subsample if being considered for the final image.
How can I say that? Well, sometimes it's filled when it isn't at 0x AA and sometimes it isn't filled when it isn't filled at 2x AA.
So, it's like if there was ONE sample, but that it wasn't at the center of the pixel: you'd get the exact same result. Sometimes it's filled while it shouldn't be, sometimes it's not filled when it should be ( that is, if you consider there should only be one sample )
-------------------- IGNORE THE FOLLOWING ----------------
Now, that seems like a good explanation. But there's more to it! I can also explain the lower AA quality of every single mode compared to ATI, and show it's a mere bug!
Look at the ATI 4x screenshort ( http://www.notforidiots.com/images/4x-aa.jpg ) and the nVidia 4x screenshot ( http://www.notforidiots.com/images/4x-aa-aggressive.jpg.
Look at the right triangle using a zoom ( such as MS Paint one :) )
Now, if you look REALLY close, you'll see something strange
There's only THREE color variations ( 33%, 66%, 100% ) . On the ATI 4x screenshot, there's FOUR color variations ( 25%, 50%, 75%, 100% )
That would indicate the GFFX 4x AA quality is, well, 3x AA!
So, the pattern is amazingly simple. In both 2x and 4x ( and possibly others, didn't check ) , there's ONE subpixel in every pixel which isn't considered when merging the subpixel buffers
-------------------- STOP IGNORING ----------------
Now, that seems a LOT like a driver bug. It's impossible to say if it's also the case ingame, or if it's just a screenshot problem. But no matter what, that's the type of bug which should ( theorically ) be very easy to fix. And NO conspiracy theories please: if nVidia did this to reduce the performance hit, the 2x AA performance hit wouldn't be so huge!
Conclusion
-------------
-------------------- IGNORE THE FOLLOWING ----------------
The 2x/QC problem is nothing more than a driver bug. It also reduces 4x AA quality. So all AA modes quality is reduced due to this bug. Performance is NOT impacted, because else 2x AA would be free ( so no conspiracy theories here, please! )
So DON'T compare the quality of GFFX/R300 AA modes right now. It's a bug, and one that should be fixed quite easily.
-------------------- STOP IGNORING ----------------
It sounds like the problem is only with 2x AA. I wasn't looking correctly at the 4x AA screenshots, the problem is that it's ordered and that cases where the 4 samples are visible are VERY rare. But they do exist!
Let's hope there's a bug with nVidia's AF algorithm too, because aggressive really looks like crap to me ( but then again, that's really unlikely )
Thanks for reading! :) I hope you enjoyed this.
Uttar
However, the 2x problem remains.
Hey,
I'm ONLY going to base myself on Anand excellent AA comparaison screenshots. Thanks a lot for taking these, BTW, Anand!
I'm mirroring the images because Anand's server is still very busy as I write this.
http://www.notforidiots.com/Images
Okay, so look at the first image:
http://www.notforidiots.com/images/off.jpg
And compare it with:
http://www.notforidiots.com/images/2x-aa-aggressive.jpg
The first is an aliased result. The second is a 2X Antialiased result on a nVidia card.
Look closely and you'll see there IS a difference: the triangles seem *smaller* with 2x AA. Why?
Well, actually, some parts are also bigger. But I'll explain why later, for now only worry about the smaller parts ( such as the bottom-right of one of the left triangle )
Well, there are more very dark pixels. But... once again, why?
Well, let's look at ATI's 2x AA now, shall we?
http://www.notforidiots.com/images/2x-aa.jpg
Now, as you see, it looks a lot smoother. But let's compre it with nVidia 2X AA ( once again, it's here (http://www.notforidiots.com/images/2x-aa-aggressive.jpg) )
Now, look at the pixels which are not filled in nVidia's 2X AA, and which are filled when there is aliasing ( here (http://www.notforidiots.com/images/off.jpg) for the aliased image again )
Try to memorize ( or use multitasking to see several images at the same time, whatever ) which spots are not filled and were without 2x AA.
Now, look again at the ATI 2x AA image ( here (http://www.notforidiots.com/images/2x-aa.jpg) )
Look at the spots that I said you to remember. Guess what? Well, they're filled on the 2x AA screenshot, but they more dark than the remaining of the triangle. And what does that tell us?
That those are the pixels that should have only one of their two subpixels filled with that triangle.
Now, as I said before , some pixels are also filled on nVidia 2x and not when there's no AA. But if you look at the ATI 2x mode, it looks there that those pixels are only filled by the triangle in 1/2 of the subpixels.
So... that means AA IS happening ( there's the performance hit ) , but the two subpixel buffers are not merged. Sometimes that means a part looks bigger, sometimes it looks smaller. But in reality, only ONE subsample if being considered for the final image.
How can I say that? Well, sometimes it's filled when it isn't at 0x AA and sometimes it isn't filled when it isn't filled at 2x AA.
So, it's like if there was ONE sample, but that it wasn't at the center of the pixel: you'd get the exact same result. Sometimes it's filled while it shouldn't be, sometimes it's not filled when it should be ( that is, if you consider there should only be one sample )
-------------------- IGNORE THE FOLLOWING ----------------
Now, that seems like a good explanation. But there's more to it! I can also explain the lower AA quality of every single mode compared to ATI, and show it's a mere bug!
Look at the ATI 4x screenshort ( http://www.notforidiots.com/images/4x-aa.jpg ) and the nVidia 4x screenshot ( http://www.notforidiots.com/images/4x-aa-aggressive.jpg.
Look at the right triangle using a zoom ( such as MS Paint one :) )
Now, if you look REALLY close, you'll see something strange
There's only THREE color variations ( 33%, 66%, 100% ) . On the ATI 4x screenshot, there's FOUR color variations ( 25%, 50%, 75%, 100% )
That would indicate the GFFX 4x AA quality is, well, 3x AA!
So, the pattern is amazingly simple. In both 2x and 4x ( and possibly others, didn't check ) , there's ONE subpixel in every pixel which isn't considered when merging the subpixel buffers
-------------------- STOP IGNORING ----------------
Now, that seems a LOT like a driver bug. It's impossible to say if it's also the case ingame, or if it's just a screenshot problem. But no matter what, that's the type of bug which should ( theorically ) be very easy to fix. And NO conspiracy theories please: if nVidia did this to reduce the performance hit, the 2x AA performance hit wouldn't be so huge!
Conclusion
-------------
-------------------- IGNORE THE FOLLOWING ----------------
The 2x/QC problem is nothing more than a driver bug. It also reduces 4x AA quality. So all AA modes quality is reduced due to this bug. Performance is NOT impacted, because else 2x AA would be free ( so no conspiracy theories here, please! )
So DON'T compare the quality of GFFX/R300 AA modes right now. It's a bug, and one that should be fixed quite easily.
-------------------- STOP IGNORING ----------------
It sounds like the problem is only with 2x AA. I wasn't looking correctly at the 4x AA screenshots, the problem is that it's ordered and that cases where the 4 samples are visible are VERY rare. But they do exist!
Let's hope there's a bug with nVidia's AF algorithm too, because aggressive really looks like crap to me ( but then again, that's really unlikely )
Thanks for reading! :) I hope you enjoyed this.
Uttar