Shimmering

[[Ch]amsalot]

Ofkafy, sfo tfhis mfodfem doefn't tfsaste sfo good.

Anyway, at least we're getting an education.

The tech report link Ryu provided supports that the GF3 FSAA is working on edges, but in a roundabout way it's working on edges:

Here's the trick with multisampling: If a pixel is on the edge of a polygon, its sub-pixels probably "belong" to different polygons which comprise different objects in a scene—a lighter object in the foreground, say, and a darker one in the background. If so, the sub-pixels will have different color values—not because of multiple texture reads per pixel, but because one pixel sits in front of another due to overdraw. If this is the case, the GeForce3 will perform a blend on the colors of the sub-pixels to determine the final color of the pixel. Thus, the chip effectively antialiases polygon edges, but not surfaces or the textures mapped to them.

Checking out further info, but one thing is sure about Voodoo5 FSAA and multisampling. It's now a matter of semantics. Voodoo5 takes multiple samples of the SAME SIZE image, hence many sites (including 3dfx at one time) called it multisampling.

-[Ch]ams

[Rags]

Originally posted by Ryu Connor


Yes, but only with it's 4x FSAA option. The 16x FAA option will not.

WRONG!!!!!!!!!

Obviously someone who has yet to play with FAA on a flight sim.

Rags

[Rags]

Originally posted by Allankyoto
So now that you guys are done arguing the technicals could someone please clarify this for me. Does the Parhelia get rid of texture shimmering with it's form of AA? That's all I want to know. Until a card does that I am not interested in upgrading from my Geforce 3.

What you are seeing is not texture shimmering, but the edges being aliased in the distance, and they move giving it a shimmering look.

FAA is very effective at eliminating that side effect.

Rags

[[Ch]amsalot]

Okay, now we get a new word from the expert..

"OVERSAMPLING"

Jees.

Multi-sampling is just like super-sampling in that you are effectively rendering at four times your base resolution, yet here all of the sub-samples share the same color value of the original sample. What is different between each sub-pixel, however, is the Z value. Each sample therefore has a unique Z value. Here is an illustration of the sub-pixels when multi-sampling is used.

http://firingsquad.gamers.com/hardware/multisamp/page3.asp

http://firingsquad.gamers.com/hardware/multisamp/default.asp

-[Ch]ams

[Ryu Connor]

http://www.tech-report.com/reviews/2001q2/geforce3/index.x?pg=16

http://www.tech-report.com/reviews/2001q4/vidcards/index.x?pg=14

http://www.tech-report.com/reviews/2001q4/r200/index.x?pg=6

http://www.tech-report.com/reviews/2002q2/parhelia/index.x?pg=9

http://www.beyond3d.com/articles/wildcatiii/index.php?page=page4.inc

http://firingsquad.gamers.com/hardware/multisamp/default.asp

http://www.xbitlabs.com/video/geforce4/

http://www.anandtech.com/showdoc.html?i=1562&p=2

http://www.3dconcept.ch/chips/chiptable6th.htm

There are the series of links that get it right.

Full Scene AA:

Rotated Grid Super Sampling:
Voodoo 5 5500

Ordered Grid Super Sampling:
GeForce 2
RADEON
Kyro and Kyro 2
RADEON 8500
Parhelia 4x mode

Edge based AA:

Multisampling:
GeForce 3
GeForce 4

Fragment AA:
Parhelia

Hybrid:

Multisampling and Supersampling (Yes, both at once.):
GeForce 4 (4XS mode)

Seems I was wrong on the details of 4XS. Sorry Cheesekeeper.

[Ryu Connor]

[Ch]amsalot:

Yes, Dave Barron's article on multisample AA details a different implementation of the technique. One not currently in use.

[Ryu Connor]

Obviously someone who has yet to play with FAA on a flight sim.

Seeing as texture shimmer is traditionally an artifact one sees on the ground in a flight sim. You know, seeing as the sky is typically a static image.

[Greebe]

Ryu have you even seen Parhelia in action to know that what you are saying is correct? I think no.

Rags, is correct.

[Ryu Connor]

http://www.ve3d.com/3dpulpit/Reviews/3dfx_5500/followup/3.html

He incorrectly labels RGSS as multisample, a fallcy touched upon by Dave Barron in his AA white paper linked earlier. Nonetheless his point of texture shimmers are true and show one of the advantages of a full scene AA and downside to edge based AA (multisample and FAA).

Obviously I have had a bit more time to play around with the effects of Full Scene Spatial Anti-Aliasing (FSAA) in games.

I do feel, however, that a bit of clarification is in order where FSAA is concerned - it is not your basic Anti-Aliasing. Basic Anti-Aliasing (AA) only resolves the problems with "stair steps" or "jaggies" - it does not cure the problem where other forms of aliasing may take place, such as "shimmering textures".

What the heck is this "shimmering"? Well, if you're a sim fan, then you will know what I'm talking about - textures on the ground do not appear to be solid, instead it appears to be moving. Another example of this would be the annoying effect as witnessed on things like fences and gratings.

Below is a simple example of what I'm talking about regarding "shimmering". The game is Half-Life with a screenshot of one of the early points in the game.

Note the circled part. It is the fenced box where the whatchamacallit comes out that starts the entire mess that is Half-Life. Now, "shimmering" is when you see the fence as not "solid" - it displays an aliasing anomaly as you pan around while looking at it. It is kinda hard to explain it here - try replicating the above scene if you have the game and pan around while noticing the fence.
Here's another example. Game is Requiem:Avenging Angel.

Ignore all outlined parts for now except those two on the "roof" - the gratings. Without FSAA, the aliasing effect is the same as the Half-Life one above - you'll see the detail on the gratings "shift", "shimmer" or move, not solid. With FSAA, the gratings are what they should be, solid.

[Ryu Connor]

Ryu have you even seen Parhelia in action to know that what you are saying is correct?

I don't need a subjective opinion to determine an objective fact. Just like I know Parhelia's FAA cannot be applied to alpha textures.

[Greebe]

Oh so in otherwords you never seen it and thus based on your extensive knowledge you are correct and those of us that actually have it are wrong?

Sorry guy but that's just too funny.

[Ryu Connor]

You're creating circle logic.

One needs not see an objective fact. If I drop an apple it will hit the ground. I don't need to demonstrate this fact in order for it to be true.

[Kruzin]

Ryu, I suggest you go back and read the original posts in this thread.
From the description of the issue, it's apparent to me that you are not understanding it correctly. He is NOT taking about texture shimmering, he is talking about aliasing that he is seeing on the horizon. For this issue, YES Parhelia's 16xFAA makes that effect go away.

[Ryu Connor]

From the description of the issue, it's apparent to me that you are not understanding it correctly.

It is? Let's go take a look.

I believe that anyone who plays games is familiar with this effect. It happens when an image moves in a game. For example when you look at the horizon in any flight simulator type of game it appears to shimmer with light as you bank your plane.

Hmm. Yes, I suppose that could be the distant terrain showing off jagged edges. Before we pass judgement though, let's take a look at his second paragraph.

The only card that I know of that totally eliminated shimmering was the Voodoo 5. The effect still shows up when I use anti-aliasing on my Geforce 3 and although I haven't tested it out yet I would assume it is still sometimes present on the Geforce 4, too.

Hmm. The RGSS FSAA solution got rid of his problem, but the MSAA provided on the GeForce 3 and 4 left it. That's odd as both cards do apply AA even to the distant rendered terrain of mountains and lands.

Hmm, but the GeForce 3 and 4 do not filter textures and the Voodoo 5 does. The Voodoo 5 solves the problem, but the GeForce 3 and 4 leave it behind.

One might be inclined to believe he's seeing texture shimmer.

[Greebe]

pffffffffff... at least I'm not techobabbling.

What Kruzin said.