GeForce 7800 GTX antialiasing investigation [Archive]

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ChrisRay

06-26-05, 04:47 AM

Geforce 7800GTX Anti Aliasing Investigation

Introduction: Last year at the release of the Nv4x hardware. Nvidia implemented Rotated Grid Multisampling for its Nv4x hardware greatly improving quality of their 4x AA and beyond modes. I took it upon myself to write up an Nv4x AA Investigation (http://www.nvnews.net/vbulletin/showthread.php?t=30641&highlight=Anti+Aliasing) where I covered the various sample patterns and hidden modes. Since the actual sampling positions for the old modes hasnt changed any. I decided it would be redundant to rehash the same material. Instead, I have decided to focus on the new modes available to the G70 owners. Namely, Transparent AA and Gamma Corrected Anti Aliasing.

Gamma Corrected: Essentially provides superior color reproduction. It can improve your subjective opinion of the image. It can have noticable effect on thin surfaces such power lines often found in games such as Call of Duty or Half Life 2. It is easily toggled off and on through the advanced options in the Nvidia control panel.

http://www.nvnews.net/articles/chrisray_iq/7800gtx/gammacorrect.jpg

Transparency Anti Aliasing: Transparent AA is a technique that can provide edge aliasing to transparent edges. Transparent edges such as alpha textures for instance have been a sore spot for many years since the introduction of multisampling. The idea is for the GPU to detect transparent textures such as leaves, grass, metallic fences (Half Life2) and properly provide anti aliasing to them. Nvidia offers both multisampling and supersampling aproaches to these new techniques which can have varied effects on the object being rendered. You can choose between multisampling or supersampling transparency or have it toggled from the control panel within the advanced settings tab.

http://www.nvnews.net/articles/chrisray_iq/7800gtx/transparency.jpg

Far Cry Comparison Shots

No AA Reference Image

http://www.nvnews.net/articles/chrisray_iq/7800gtx/g70noaa.png

Thoughts: This was a very difficult comparison to make. The hovering leaves and bobbing effect made taking an exact screenshot a bit difficult. Please bear with any minor inconsistencies you might see. While the results are not perfect I am very satisfied with what they represent.

2x AA Comparisons (http://www.nvnews.net/articles/chrisray_iq/comparison/2xpattern.jpg)

2xAA/16xAF

http://www.nvnews.net/articles/chrisray_iq/7800gtx/2xAAnorm.png

2xAA/16xAF (Gamma Corrected)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/2xaagamma.png

2xAA/16xAF (Gamma Corrected, Transparent Multisampling)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/2xtmaagamma.png

2xAA/16xAF (Gamma Corrected, Transparent Supersampling)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/2xtsaagamma.png

Thoughts: With Far Cry I decided to focus on the leaf textures of the bush. As can be seen here. 2xAA does a reasonable job of cleaning up some of the aliasing along the beams. The textures of the bush however are not anti aliased at all. Once you enabled transparent multisampling, the aliasing is blurred out along the leaves. Under this circumstance it appears multisampling is more effective than super sampling.

4x AA Comparison (http://www.nvnews.net/articles/chrisray_iq/comparison/4xpattern.jpg)

4xAA/16xAF

http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xaanorm.png

4xAA/16xAF (Gamma Corrected)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xgamma.png

4xAA/16xAF (Gamma Corrected, Transparent Multisample)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xtmaagamma.png

4xAA/16xAF (Gamma Corrected, Transparent Supersample)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xtsaagamma.png

Thoughts: Seeing the usual step up from 2x to 4x shouldnt come as any surprise to anyone. However the impressive leap in quality from transparent multisampling should readily noticable on the leaf textures. Once again it seems transparent multisampling is doing a better job of removing edge aliasing from the bush.

8x AA Comparison (http://www.nvnews.net/articles/chrisray_iq/comparison/8xSpattern.jpg)

8xAA/16xAF

http://www.nvnews.net/articles/chrisray_iq/7800gtx/8xSnorm.png

8xAA/16xAF (Gamma Corrected)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/8xSgamma.png

8xAA/16xAF (Gamma Corrected, Transparent Multisample)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/8xStmaagamma.png

8xAA/16xAF (Gamma Correct, Transparent Supersample)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/8xStsaagamma.png

Thoughts: The nature of supersampling automatically gives a large quality enhancements to the bush leaves. It can still however cause a notable performance hit. Enabling transparent multisampling and gamma correction reduce aliasing to unseen levels in Far Cry.

Far Cry Multi AA Comparison Screenshot (http://www.nvnews.net/articles/chrisray_iq/7800gtx/fc_multi.png)

Note: Special thanks to Clay for helping me with the multiple comparison.

Performance

http://www.nvnews.net/articles/chrisray_iq/7800gtx/farcrygraph1.png

http://www.nvnews.net/articles/chrisray_iq/7800gtx/farcrygraph2.png

Performance Thoughts: The first thing you'll notice is that a Geforce 7800GTX SLI setup is CPU limited up to 4xAA at 1600x1200 resolution. Meaning image quality enhancements are practically free. The 4xAA Gamma correction tests seem to be the oddball here. Showing a drop in performance thats not consistent with 2x or 8x. I imagine this is a bug as it only happens with Far Cry. The other thing you might notice is how there is a difference in performance drops with transparency AA based off the two map graphs. This is because of whats actually being rendered. Indoor Far Cry scenes such as archive do not generally have much foliage or transparent textures. And in this case there are none in the archive maps. The river map however is filled with trees, grass, and a great deal of transparent foliage. The hardware definately seems capable of detecting transparent textures and only taking additional rendering performance when neccasary.

Note: 8xAA has some troubles scaling with Far Cry (http://www.nvnews.net/vbulletin/showthread.php?t=47710). People with single cards should see a more consistent framerate drop when turning on 8xAA.

Minor Update: Gamma Correction performance at 4xAA is a known bug and will be fixed in later drivers. Gamma correction now occurs on the Nvidia DACS with no performance hit. Also just as with Half Life 2 there is also a known bug that causes textures to be missing with transparent supersampling. It will be fixed in future drivers.

ChrisRay

06-26-05, 04:48 AM

Half Life 2 Comparison Shots

No AA Reference image

NoAA/16xAF

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hlnoaa.png

Thoughts: For these screenshots you may wish to adjust your gamma some. My reasoning for taking them so dark was to highlight the effects with various lighting conditions. Gamma correction would skew the results and defeat the purpose of the test. Keep in mind theres an odd bug with TSAA that is being fixed in future drivers. The fence line is white and without texture with transparent super sampling enabled.

2x AA Comparisons (http://www.nvnews.net/articles/chrisray_iq/comparison/2xpattern.jpg)

2xAA/16xAF.

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl2xnorm.png

2xAA/16xAF (Gamma Corrected)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl2xgamma.png

2xAA/16xAF (Gamma Correct, Transparent Multisampling)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl2xtmaagamma.png.

2xAA/16xAF (Gamma Correct, Transparent Supersampling)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl2xtsaagamma.png

Thoughts: 2xAA represents a slight improvement to overall image quality. If you look across the power lines as well you can see a small improvement by the implementation of gamma correction. Transparency AA represents a significant improvement to image quality. Paticularly the super sampling implementation. While multisampling seems to have a lower overall effect. However there is much room for improvement.

4x AA Comparison (http://www.nvnews.net/articles/chrisray_iq/comparison/4xpattern.jpg)

4xAA/16xAF

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl4xnorm.png

4xAA/16xAF (Gamma Corrected)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl4xgamma.png

4xAA/16xAF ((Gamma Corrected, Transparent Multisampling))

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl4xtmaagamma.png

4xAA/16xAF (Gamma Corrected, Transparent Supersampling)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl4xtsaagamma.png

Thoughts: 4xAA shows a pretty significant overall improvement in image quality. Gamma correction provides a slight subjective improvement to the overall image including power lines. Transparent Supersampling once again making a significant improvement to the chain link fence.

8xS AA Comparison (http://www.nvnews.net/articles/chrisray_iq/comparison/8xSpattern.jpg)

8xAA/16xAF

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl8xnorm.png

8xAA/16xAF (Gamma Corrected)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl8xgamma.png

8xAA/16xAF ((Gamma Correct, Transparent Multisampling))

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl28xtmaagamma.png

8xAA/16xAF ((Gamma Correct, Transparent Supersampling))

http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl28xtsaagamma.png

Thoughts: The supersampling nature of 8xS once again provides an instance boost to the overall scene effectively removing significant aliasing from the chain link fence. Enabling transparent super sampling creates a beautiful image with almost no visible aliasing.
Half Life 2 Multi AA Comparison Screenshot (http://www.nvnews.net/articles/chrisray_iq/7800gtx/hl2_multi.png)

Note: Special thanks to Clay for helping me with multishot.

Performance

http://www.nvnews.net/articles/chrisray_iq/7800gtx/aahalflife2.png

Performance Thoughts: I realised that Half Life 2 would show signs of CPU limitation (http://www.nvnews.net/vbulletin/showthread.php?t=47710) when next generation hardware came around. But I didnt realise it would be this severe. . There are rare cases where performance drops lower to what you see here generally providing excellent performance and image quality. Modern 7800 cards are significantly CPU limited in this title and can get away with 8xAA on SLI setups or 4xAA on non SLI setups with Transparency Supersampling enabled for unheard of quality improvements from anything we've seen before

Final Thoughts and Conclusions: For the last 7 months I have been pretty consistent in saying anti aliasing would take a back seat to new technology improvements. I am willing and happy to admit I was wrong about this. My biggest criticism with the current trend of raising sample pattern density was that it increased framebuffer consumption considerably. However the new modes are not only able to increase quality but they manage to do it without affecting performance too much. Add this to the fact that Nvidia has the best legacy anti aliasing modes (http://www.nvnews.net/vbulletin/showthread.php?t=30641&highlight=Anti+Aliasing) available. I am left very satisfied by the improvements made to the Geforce 7800GTX. With these new modes transparent texture problems should be a thing of the past.

Final Note: I would also like to point out I took screenshots comparing World of Warcraft with Normal 4xAA (http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xnotrans.png) and 4x Transparent Supersampling (http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xtrans.png)

ChrisRay

06-26-05, 04:50 AM

Well. That was some work. Hope you guys like it. Oh I unlocked the thread. ;)

Lfctony

06-26-05, 05:03 AM

Nice job Chris. :)

killahsin

06-26-05, 05:10 AM

very nice job.

Demirug

06-26-05, 11:01 AM

ChrisRay, the current driver have a bug that cause a performance drop with same games if you use gamma correction. nVidia already know this.

NoWayDude

06-26-05, 05:29 PM

ChrisRay

06-26-05, 08:20 PM

ChrisRay, if you have Far Cry, could you check something?
This happened to me while playing
AA and AF from ingame setting.
TASS On on NV CP
http://img170.echo.cx/img170/1593/farcrytass4vz.th.jpg (http://img170.echo.cx/my.php?image=farcrytass4vz.jpg)

TAMS on NV CP
http://img170.echo.cx/img170/5005/farcrytams0bw.th.jpg (http://img170.echo.cx/my.php?image=farcrytams0bw.jpg)

Game is patched to 1.32 version, and gamma correction is on
Just interested to know if this a bug with (possibly) the patch, or the driver as Demirug mentioned
Feedback would be apreciated

Yes, its a known and documented bug. I found out the hard way too. :)

ChrisRay, the current driver have a bug that cause a performance drop with same games if you use gamma correction. nVidia already know this.

Thanks. I was pretty sure it was. I couldnt see any other possible explanation for it.

Skinner

06-26-05, 08:30 PM

Chris, what drivers are you using, I cann't even start Far Cry (with 77.72))

ChrisRay

06-26-05, 08:32 PM

Same Drivers, Are you running Windowx 64 or something? Have you patched to 1.3?

*Edit* I made a few updates so the known bugs would better illustrated.

Chris

Skinner

06-26-05, 08:35 PM

Same Drivers, Are you running Windowx 64 or something? Have you patched to 1.3?

*Edit* I made a few updates so the known bugs would better illustrated.

Chris

No just XP 32 bits. and I have patch 1.3, 1.31 and 1,32. The splash screen loads and then nothing.

Edit,
i just fixed it problem solved.

ChrisRay

06-26-05, 08:45 PM

No just XP 32 bits. and I have patch 1.3, 1.31 and 1,32. The splash screen loads and then nothing.

Edit,
i just fixed it problem solved.

What did you do? I havent had a single problem.

Skinner

06-26-05, 09:05 PM

What did you do? I havent had a single problem.

My DVDplayer appears to have a problem, it wouldn't spin up with the Far Cry CD, so I tried my other CDplayer. It took me almost one day to figger that out :D

ChrisRay

06-26-05, 09:10 PM

My DVDplayer appears to have a problem, it wouldn't spin up with the Far Cry CD, so I tried my other CDplayer. It took me almost one day to figger that out :D

Hehe! You could also try mounting an image on your HD. Or the easiest solution. Use a No CD crack. I hate requiring my CDs to plau games. :) Either way.. Far Cry looks amazing @ 4xAA/16xAF Gamma Corrected, Transparent Multisampling @ 1600x1200.

Skinner

06-26-05, 09:17 PM

Hehe! You could also try mounting an image on your HD. Or the easiest solution. Use a No CD crack. I hate requiring my CDs to plau games. :) Either way.. Far Cry looks amazing @ 4xAA/16xAF Gamma Corrected, Transparent Multisampling @ 1600x1200.

Yeah a no CD comes in handy, the greatest pain in the ass is the Splintercell CT DVD check everytime.

Well, finally I can check it out, transparant ms is so nice for vegetation

SH64

06-26-05, 10:17 PM

Great work Chris ! .. the new AA modes look cool. now we have more image enhancments to fiddle with before playing a new game & more to change the old look of a games we already played like FC & HL2 :D (of course that goes for the 7800 owners only)

EDIT : BTW how comes the foliage in FarCry's TMAA shot looks better than the TSAA one :confused: .. i always thought SuperSampling provides best IQ ?

Bubba

06-26-05, 10:55 PM

ChrisRay

06-26-05, 10:57 PM

Awesome job ChrisRay! Did you notice that in the Far Cry shots that the hanging thatch roofing on the far building is missing from all the Gamma Corrected, Transparent Supersampling shots? I didn't notice anything missing on the Half Life examples. Did you happen to see any other missing tectures or anything during your other tests?

Yes, I updated the thread to make a note that some textures are missing in Far Cry currently this morning. This issue should be a thing of the past when new drivers come out. Like everyone else I went ahead and ran IQ comparison and just made a note of the bugs.

Also the Half Life 2 shots do have a bug. Missing texture along the fence. :) But the bug shouldnt be in future drivers.

jAkUp

06-27-05, 01:30 AM

Just got around to checking the final now :D Awesome job Chris! You do the work that the rest of us are too lazy to do :D :D :D

Kombatant

06-27-05, 04:53 AM

ChrisRay, excellent job man :) One question: have you noticed any situations where Transparency AA set to Multisampling has a noticeable effect? Because to be honest, I haven't seen such a thing yet.

ChrisRay

06-27-05, 05:02 AM

ChrisRay, excellent job man :) One question: have you noticed any situations where Transparency AA set to Multisampling has a noticeable effect? Because to be honest, I haven't seen such a thing yet.

World of Warcraft and Far Cry have both showed nice improvements with transparency multisampling on foliage. ((though the foliage tends to blur a bit but thats multisampling for you)

Did you not see my bush comparison? ;)

(transparency multisample)

http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xtmaagamma.png

4x Normal

http://www.nvnews.net/articles/chrisray_iq/7800gtx/4xaanorm.png

Kombatant

06-27-05, 07:48 AM

Yes I did, but you've got to admit the effect is not very evident with the naked eye while you're playing. TSS though is.

ChrisRay

06-27-05, 08:00 AM

Yes I did, but you've got to admit the effect is not very evident with the naked eye while you're playing. TSS though is.

To me I see it removing the shimmering effect of crawling edges along the leaves with either TMAA or TSAA in Far Cry while in motion. I think TMAA actually does a better job in Far Cry honestly. But in all honesty, I think its one of those things an IQ nut will notice. And of course the higher resolution you play in the even less noticable it be. But thats a problem anti aliasing has in general. I dont paticularly feel TSAA is any better in this game. And in both WoW/Far Cry it made a difference for me.

P.S. I'm gonna have to respectfully disagree. Since I have already found two games where Transparent Multisampling has made an affect on the foliage being rendered. Makes me wonder if EQ 2 would see an improvement.

Kombatant

06-27-05, 08:40 AM

ChrisRay

06-27-05, 08:50 AM

I think we're arguing over scemantics here man :) Maybe my english need some improving... I didn't say that I can't notice an improvement, I just said that it's not evident enough, as it is when you use TSAA. I will check again about Far Cry foliage, since I paid more attention to Half Life 2 tbh (where in fences TMAA hardly does any difference, if any).

Agreed. Half Life 2' shows absolutely nill difference with transparent multisampling. I felt that Far Cry/WoW showed a nice improvement though :) Thats the reason I opted to include Far Cry in this comparison because it became a somewhat common misonception that TMAA didnt do anything for IQ due to those Half Life 2 shots. Which is IMO not the reviewers fault. But the time constraints ((I mean the review cards really werent out until the very end.)) Not enough time to do any real indepth analysis and most people just used the images nvidia reccomended with the biggest improvements.

But either way I guess I got confused by what you said. Since I finally have gotten back to WoW. I have really gotten a chance to see it in action. ((That game is loaded with Foliage that had this kind of problem)) And its really beautiful and has to be seen to be appreciated.