Shimmering

[Allankyoto]

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.

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.

So my question is, 'Does the Parhelia with 16x antialiasing on, totally elminate shimmering?'

If it does then I will seriously consider picking one up.

[Ryu Connor]

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.

So my question is, 'Does the Parhelia with 16x antialiasing on, totally elminate shimmering?'

The GeForce 3 and 4 can't get rid of the shimmering you are seeing because it uses an edge based AA. Where as the V5 and GF2 both used a full scene AA method, which improves image quality and removes the artifacts you are mentioning.

The 16X AA on Parhelia is also edge based and so it too will be unable to remove the artifact your are seeing. You would have to use an ATI card with it's Smoothvision (which is not ideal due to poor driver compatibility with flight sim apps) or the 4X FSAA mode presented on the Parhelia.

[Allankyoto]

Well I think I'm confused. I was under the impression that any of the Geforce line of cards use full scene antialiasing and the quality is basically the same. The effect is on the all parts of the screen.

As for the Radeon cards I'm not exactly sure of their implementation but I thought Smoothvision was just another form of full scene AA.

From my understanding, Parahelia uses an edge based form of AA that is better suited to eliminating the unwanted shimmering. I thought it was the only gaming card on the market today with that feature. That is also the reason why you see it doing 16x versus everyone elses 4x.

Hmmm. Anyone care to shed some more light on this matter?

[Cheesekeeper]

This very debate is currently going on in this thread:

http://forums.murc.ws/showthread.php?s=&threadid=33991&pagenumber=7

It is my understanding that the Pahelia is the only current card to use an Edge-AA like approach. NVidia's technical documents on antialiasing describe the full AA process utililised by their cards - there is no mechanism to detect which part of the image is to be antialiased.

My current GF3 has the shimmering effect in spades. Hopefully one of the Parhelia beta-testers here can jump in to confirm whether this effect is noticable on the Parhelia.......

[103er-Fan]

Originally posted by Allankyoto
Well I think I'm confused. I was under the impression that any of the Geforce line of cards use full scene antialiasing and the quality is basically the same. The effect is on the all parts of the screen.

Hello there!
There are currently two major forms of Anti-Aliasing:
Supersampling (3dfx, ATI, Matrox, PowerVR) and Multisampling (nVidia). While supersamlping offers better quality, multisampling offers better performance.
Basicly supersampling filters the whole scene: If you use it with a 1024x768 resolution, the graphics card renders the pic with a higher resolution and resizes it back to 1024x768 with the anti aliased scene, including textures.
Multisampling also does AA on the whole scene, but it doesn't filters the textures, so it saves some fillrate.
Both methods are called FSAA (Full Scene Anti Aliasing), Matrox' new method is called FAA (Fragment Anti Aliasing), which means it only renders some parts of the scene in a higher resolution. It "scans" for the edges, renders it in a higher resolution and inserts it to the final scene, that saves bandwidth and fillrate.*

ATI's Smoothvision is just another type of Supersampling, I am not really sure about it's specific features, but I heard something about that it's programmable by the developers

To reduce the shimmering, you might want to try Aniso-Filtering, most of the modern cards are offering this feature, especially the Radeon 8500 can do that very good.


*Note: That is how I understood the AA technics, maybe I am wrong, but I think nggalai might have some better comments on this.

[Cheesekeeper]

Originally posted by 103er-Fan

To reduce the shimmering, you might want to try Aniso-Filtering, most of the modern cards are offering this feature, especially the Radeon 8500 can do that very good.

Not sure about that bit - the shimmering occurs along the edges of antialiased objects. Anisotropic filtering as I understand it only applies to surface textures. Filtering should have no impact on the shimmering effect......

[103er-Fan]

Originally posted by Cheesekeeper


Not sure about that bit - the shimmering occurs along the edges of antialiased objects. Anisotropic filtering as I understand it only applies to surface textures. Filtering should have no impact on the shimmering effect......

I am not sure about that one as I stated, I am currently using a Voodoo5 5500 which doesn't offer AF, but since I have great supersampling, the shimmering effect doesn't appear
I used a Radeon 8500 for a few months though, but I haven't noticed the effect on this card either, maybe also because of it's supersampling, but I had also set the AF level to maximum, because the performance hit was very small.

[Cheesekeeper]

It's interesting that (with the possible exception of the Parhelia), the V5500 still offers the best quality AA. On the Geforce cards the shimmering effect is sometimes bad enough that it's better to turn of AA altogether.

The NV30 should be interesting, since it should be the first chip jointly designed between the NVidia and ex-3dfx designers. Hmmm, "Geforce Voodoo" has a nice ring to it

[Ryu Connor]

There is no debate. WaltC and you are wrong. If you won't believe Scott or me, perhaps you'll take Kert at his word. He even provides pictures.

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

'SmoothVision': super- or multi-sample anti-aliasing?
R200's implementation of anti-aliasing has been aptly named 'SmoothVision'. In order to uncover the type of anti-aliasing that R200 uses, it is necessary to understand the concepts behind super-sampling and multi-sampling. In super-sampling, each frame is first rendered at a higher resolution. The image thus generated is then downscaled to the desired resolution with a suitable filter, usually bilinear. In this way, the textures and edges of objects that make up the image are anti-aliased. Multi-sampling, on the other hand, concentrates mainly on anti-aliasing object edges. Depending on the particular implementation, multi-sampling may or may not filter textures. In the GeForce3, textures are not anti-aliased.

Texture anti-aliasing
This difference between the two modes of anti-aliasing provides a way to recognize the type of anti-aliasing. But how does one recognize anti-aliased textures? The difference between filtered textures (e.g. bilinear, trilinear filters) and anti-aliased filtered textures is subtle indeed and by no means foolproof. The solution, as it turns out, is to disable texture filtering and use point sampling instead. With GeForce3 style multi-sampling, we note that edges are anti-aliased while textures remain point sampled (Figure 8). R200 'SmoothVision' anti-aliases object edges and their textures (Figure 8).

Me:

The Parhelia does two types of AA. FSAA and FAA. The 4X mode is a FSAA so it samples the whole scene. That mode will fix texture shimmer. The 16x FAA mode is an edge based AA so it does not sample the whole scene and thus you will get shimmering.

ATI's card does full scene super sampling. Therefore it too will get rid of texture shimmering. You can get this same effect on the GeForce 2 line and the older Voodoo 5 line of cards.

[Cheesekeeper]

Ryu, I'd like to believe you, but you may need to explain this to NVidia's designers as well. They have full documentation on their AA methods here:

http://www.nvidia.com/docs/lo/1451/SUPP/accuview.final.pdf

They make no mention of any sort of edge detection, and the document even goes into detail as to how they counter the effects the AA algorithm has on textures.

I'm looking at a GF3 right now, and if AA isn't burring up the textures when AA is enabled, I'd be very curious to know what is. I'm quite willing to accept the possibility that I'm wrong on this, but there does seem to be a lot of confilicting information floating around........

[Ryu Connor]

I don't see where that document contradicts anything Scott, Kert, or myself have said.

I'm looking at a GF3 right now, and if AA isn't burring up the textures when AA is enabled, I'd be very curious to know what is.

Quincunx will reduce image quality. Try the 2x or 4x mode. Despite everything you still have not answered the key question.

If the GeForce 3 and 4 don't do edge AA, then why do they suffer texture shimmer? As we already know that a full scene AA solution will remove those artifacts.

[Cheesekeeper]

Quote from the NVidia tech brief:

4x and 4XS Modes: Higher Level of Texture Quality
4XS mode is a new high-quality mode that delivers improved subpixel coverage and
a higher level of texture quality.
When the final color of a pixel is determined, all of the subpixels that can contribute
to the final pixel color are tested. They are either in or out (that is, they
contribute by being part of the object and that object covers the subpixel, or they
don't). The final pixel color is then reconstructed by implementing a weighted
summation of all of the subpixels. 4XS mode delivers 50 percent more subpixel
coverage than previous modes. This translates into a finer gradation in final pixel
color values at the edge of an object, resulting in a smoother antialiased edge.
Additionally, 4XS mode delivers a higher-quality image by delivering more texture
samples per pixel.
-------------------------------------------------------------------------------

If the AA algorithm does not affect the textures, why do their AA modes have to deal with texture samples?

[Ryu Connor]

If the AA algorithm does not affect the textures, why do their AA modes have to deal with texture samples?

Because textures have edges. That and were still only talking about subpixel data. Not the texture itself.

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

The placement of MIP maps differs between super- and multi-sample anti-aliasing. Let's define the process of MIP mapping. MIP mapping provides a sequence of texture maps wherein the first texture map is an uncompressed texture map. Subsequent texture maps are downscaled by a fixed ratio until the texture map has been compressed to a single texel. This process may be visualized as a pyramid of MIP maps (Figure 9). When texturing an object as a perspective view, the graphics processor accesses one of the sequence of MIP maps to retrieve the appropriate texel, taking into account screen resolution and distance. As the closer portions of the perspective object are being rendered, the rendering circuitry accesses the less compressed MIP maps.

Recall that super-sampling renders at high resolution in the initial phase. There is, therefore, an emphasis towards MIP maps of higher detail than in GeForce3's multi-sampling. Figure 10 is a composite of two screen captures from OpenGL-based 'Serious Sam', with color-coded MIP map levels. The screen capture on the right (R200) has a higher level of detail compared to the screen capture on the left (GeForce3). Clearly, 'SmoothVision' is a form of super-sampling.

Me:

It's then followed by a picture. Their AA modes are edge based, but options like Quincunx for example takes three non-subpixel values from the texture in order to introduce a blurring.

It appears that 4XS only deal with subpixel data. It does not appear to take the texture itself and filter it as a full scene AA solution would.

[[Ch]amsalot]

I cannot believe the amount of misinforamtion and utter lack of knowledge exhibited by some of the members of this forum with respect to FSAA.

The number of misstatements are too great to quote, so I will simply set the record straight here.

For those of you who said anything contrary to the following, you should be ashamed of yourselves.

Voodoo5 uses MULTISAMPLING, FSAA. Specifically, it employed a pixel-jittering (pixel-shifting) MULTISAMPLING technique, on the full scene, which provided the best ability to reduce shimmering.

GeForce, GeForce2, and GeForce3 (not-Quincunx mode)
These cards all used SUPERSAMPLING FSAA. With Supersampling, the 3d card internally renders larger samples of the scene and then filters them down to the output resoltution, reducing jaggies in the process. This is VERY SLOW, and not as effective as Mutisampling at reducing shimmering or pixel pop-up.

GeForce3 (quincunx mode). This is a mutisampling FSAA.

GeForce4 (all versions). NVIDIA went back to the drawing board and uses MULTISAMPLING for GeForce4 (both Ti and MX) FSAA.

ATI RADEON: ATI Radeon's hardware is capable of supporting high-quality MULTISAMPLING, but last I heard it was still not supported in the drivers. Instead, Radeon is still using the super-slow SUPERSAMPLING.

Matrox Parhelia: Matrox Parhelia uses two methods (user selectable) 16X FAA (Fragment anti-aliasing, employed on edges only) or 4XFSAA (SUPERSAMPLING).

Any futher questions I'll be happy to address. But again, if you don't know what you're talking about you should preface your opinions with "I don't know what I'm talking about."

Yeesh!
-[Ch]amsalot

[Ryu Connor]

Voodoo5 uses MULTISAMPLING, FSAA. Specifically, it employed a pixel-jittering (pixel-shifting) MULTISAMPLING technique, on the full scene, which provided the best ability to reduce shimmering.

Actually it used RGSS also known as Rotated Grid Super Sampling.

That and the GeForce 3 does multisampling. Not super sampling.

But again, if you don't know what you're talking about you should preface your opinions with "I don't know what I'm talking about."

Heh. Thanks for the preface.

This is VERY SLOW, and not as effective as Mutisampling at reducing shimmering or pixel pop-up.

Wow. Don't know how I missed this glaring error first go round. You're thinking of super sampling.