http://www.eurogamer.net/article ... oteur-aa-blog-entry

AA=anti-aliasing 反鋸齒技術

在最新跨平台遊戲Pandemic's The Saboteur對比中，發現在對比沒有AA的360版情況下，PS3版擁有很高質量的AA效果





開發者在US PlayStation Blog上說：使用了SPU進行全屏AA，另外上面對比圖可以看出360版和神機版使用了不同的光照模型。
beyond3D的好事者發現Sony是在自主技術的跨平台引擎PhyreEngine中實現了類似[B]MLAA[/B]的技術。





實現MLAA出來的效果讓人振奮，據eurogamer陳述，在最好的情況下MLAA可以獲得比16XAA更好的圖像質量

MLAA是什麼？在這裡可以看到詳細介紹。MLAA（morphological antialiasing）是Intel正在玩的，完全基於CPU處理的AA解決方案，這種方案從未在任何遊戲使用過，包括PC遊戲，估計Intel研究這是是將該技術應用在未來出品的GPGPU Larrabee上。但是現在將會看到Sony在Cell上對其的實現效果，包括在未來EA出品的跨平台遊戲BFBC2上可能會看到該技術。





===================================================================================================================================================================================================================
DF on Saboteur's PS3 anti-aliasing
December 9th, 2009


Update: This morning, Christer Ericson, director of tools and technology at Sony Santa Monica and part of the hugely respected God of War team, got in touch to set us straight on the technical background to the effect seen in The Saboteur. Christer's knowledge on this subject obviously far outstrips our own and he took issue with several points in yesterday's article, which you can still read in full below this update.
Firstly, the definition of MLAA[/COLOR] isn't in keeping with the basic outline of the technique as it has been described by some Pandemic staff, and it is almost certainly an extension of the edge-filter plus blur technique seen in several cross-platform titles already. As Christer says, "the qualitative difference comes down to how you edge-detect and how you 'blur'."
The screenshots may not be showing MLAA, and it's almost certainly not a technique as experimental as we thought it was, but it's certainly the case that this is the most impressive form of this type of anti-aliasing we've seen to date in a console game. Certainly, as we alluded to originally, the concept of using an edge-filter/blur combination isn't new, and continues to be refined. This[/COLOR] document by Isshiki and Kunieda published in 1999 suggested a similar technique, and, more recently, AMD's[/COLOR] Iourcha, Yang and Pomianowski suggested a more advanced version of the same basic idea.
In terms of the effectiveness of luminance for determining edges, Christer also pointed out that the pixels we've highlighted as causing problems for edge-smoothing in The Saboteur aren't a product of red meeting black, but actually brown and red - similar in terms of luminance values and thus more likely to cause that particular artefact.
It's fair to say that in our excitement about the level of image quality displayed in The Saboteur, we were off-beam to be so definitive about MLAA as the technique being used, but it is still a great example of the SPUs being used to do post-processing work more traditionally associated with the GPU and, in this case, producing arguably better results than the more generally accepted MSAA solutions built into the graphics hardware. Thanks to Christer for getting in touch.
Original story: If there's one element of multi-platform development that comes up repeatedly in our Face-Off coverage, it's the implementation of anti-aliasing on current-generation HD consoles.
It's often the case that the Xbox 360 version of a game features edge-smoothing, while the PlayStation 3 counterpart will either leave it off altogether, scale it back, or use an NVIDIA specific technique called "quincunx", which refines edges nicely, but blurs the entire texture in the process.
None of these options are particularly attractive (though quincunx has its place in certain scenarios), and neither is blurring the entire screen, which other people do; the so-called Vaseline effect. However, recent games like Brutal Legend and Overlord II on both console platforms have tried out another technique - seeking out just the edges themselves and blurring them, leaving texture detail intact. It's better than nothing but still not actually that good.
The PS3 rendition of Pandemic's The Saboteur is different though. It's special. It's trying something new that's never been seen before on console, or indeed PC, and its results are terrific. In a best-case scenario you get edge-smoothing that is beyond the effect of 16x multi-sampling anti-aliasing, effectively delivering an effect better than the capabilities of high-end GPUs without crippling performance. Compare and contrast with Xbox 360 hardware, which tops out at 4x MSAA.
Let's kick off with a quick comparison of the effect in play on both versions of the game. It's interesting to point out that both Xbox 360 and PC versions of The Saboteur have no support for anti-aliasing whatsoever. It's just the PS3 owners that get the love, for reasons explained later. While the lack of AA in the Xbox 360 version is a bit disappointing, for the purposes this piece it's a bit of boon as it effectively gives us a "before and after" means of better understanding the PS3 technique.



The Saboteur on 360 has no anti-aliasing, making it a good comparison point up against the PS3 version with its new edge-smoothing technique. The difference in lighting, along with other matters, is something we'll cover in the next Face-Off.
So how is it done? Well, in the comments section of one US PlayStation Blog post[/COLOR], Pandemic's Tom French talked about "using the SPUs to do a full-screen FSAA filter". The satellite processors within the Cell chip are excellent for extremely fast processing of limited batches of data, making them perfect for the task at hand, which is to process the entire framebuffer seeking out all edges and then blending them.
Posters on the Beyond3D forum[/COLOR] soon began to investigate. It's a technique initially put forward by Intel, but best described with examples in this blog post[/COLOR] which shows the real potential of the technique, and how it compares with the Brutal Legend method of edge-blurring. There is no real competition here. The so-called morphological anti-aliasing (or MLAA) seen in The Saboteur is leaps and bounds ahead of anything we've seen so far when it works in optimum conditions.
Being experimental, it does have its drawbacks. When edges in-game are one pixel or less than one pixel in thickness, the edge-detection technique doesn't really work. Pandemic also subjects the entire, completed framebuffer to analysis - including the HUD elements - so there is often artefacting on the text overlays. This is probably unavoidable in this game: while the GPU starts to draw the next frame, the SPUs are busy with the AA and for that situation to take place the completed frame will need to be analysed.
Pandemic is keeping mum on the AA technique, though some tidbits have apparently leaked from the developers on the NeoGAF forum. According to these posts, the filter is applied to the luminance of any given scene. It's a really clever way to maintain speed, but on the other hand, some colours - red and black for example - have similar luminance levels, so the filter picks up the majority of edges but misses others. Additionally, in some cases there are some interesting "fuzzing" issues on edges, which without some more illumination from the coders is very difficult to explain. Perhaps it's simply the effect of processing a motion-blurred screen?





While the edge-smoothing properties are astonishing, it comes at the cost of a few artefacts as you'll see by clicking on each thumbnail. Thankfully they barely impact on the quality of the overall presentation.
Overall then, what we have in The Saboteur on PS3 is very much an experimental technique, and you get the idea that the base visuals suit the technique well. In playing the Xbox 360 version, the level of "teh jaggies" isn't exactly a major issue; the game lacks high-contrast edges, and is pretty soft in general. In this environment, the MLAA technique employed by Pandemic works beautifully and in most cases you really need to look hard for the artefacts. But they are there, and you wonder how well the technique would work on higher contrast games like Battlefield: Bad Company 2, Halo 3 or the almighty Uncharted 2 where the MLAA would really have its work cut out.
In the meantime, what we have is something that's new and genuinely exciting from a technical standpoint. We're seeing PS3 attacking a visual problem using a method that not even the most high-end GPUs are using. You can't help but wonder whether MLAA, in combination with MSAA and a filter to weed out the artefacts, couldn't be hardware-integrated in the next generation consoles.
It'll also be interesting to see whether MLAA returns in other PS3 cross-platform projects before then, because it looks extremely good in action. Chances are it will come down to how computationally expensive the technique actually is on the SPU, and how it can be refined still further, and that's where our knowledge hits a brick wall. If any ex-Pandemic staff want to share more on the MLAA implementation, feel free to get in touch...

[ 本帖最后由 harry8888 于 2009-12-11 13:59 编辑 ]

樓上沒下文，所托非人.....

所謂模糊其實是錯覺。
以現在的主機機能，包括PC，都是無法做到真正質量的貼圖。
做不到的話就要壓縮，貼圖被壓縮就會變成馬賽克，鋸牙的出現就是因為馬賽克，AA就是爲了抗這些問題而出現的。
所謂越高級的AA，抗馬賽克就會越好，但是這些馬賽克一旦被抗，就會變得平滑，也會出現模糊的錯覺。
因為貼圖是馬賽克，如果被抗掉馬賽克邊緣就會變得平滑，錯覺是模糊。所以誕生了AF。
目前比各方面效能QAA是比4aa高級更好的。也可以說平手。
如果還加MLAA的話，360那廢柴4aa是只有被秒的份。
以下MLAA抗馬賽克保持質量對比。
左圖馬賽克導致殘渣，所以說模糊其實是錯覺。右圖已經MLAA。




QAA可以看這裡。
http://club.tgfc.com/thread-6091528-1-8.html

現在就連孤島危機的貼圖都有馬賽克，試問還有那個遊戲沒的。
不壓縮貼圖的話，恐怕跑不動...呵呵
這是記憶體和處理能力的問題，尤其那種垃圾主機性能，馬賽克特別嚴重。就像爲什麽PS1沒AA特別多馬賽克+鋸牙，而360沒AA就比較少，這就是性能跑不動壓縮的結果。就連PS1生化危機的原質真實背景貼圖都是馬賽克。可想而知。
還有，導致鋸牙不只是壓縮馬賽克貼圖的功勞，還有很多因素都會導致鋸牙形成。
當然，壓縮馬賽克圖是最先影響的問題。寫輪眼哪裡會考慮到這些呢。
不過話說爲什麽不直接用CG貼圖呢，跑不動、怎樣用，乖乖的把質量壓掉吧。連這點常識都沒就在這裡吵。。呵呵

[ 本帖最后由 harry8888 于 2009-12-11 21:36 编辑 ]

一、鋸齒的形成

像素（Picture element）是顯示設備中構成圖像的最小單位，雖然像素非常的小，但是無數像素組織在一起才構成了一幅完整的圖畫，每一個象素都佔據著畫面上的某個區域。像素在色彩緩衝區或屏幕中以一組整數類型的二維坐標(x，y)表示當前位置，如果在實際計算得到任何坐標為浮點數值的像素，該浮點數將被轉換為整數坐標。

舉個例子：在遊戲中，白色背景下，飛過一個黑色物體，若黑色物體的某坐標為100的話，畫面表示則是第100個像素是黑色，第101個像素是白色。若黑物體的坐標不是整數100而是浮點數100.1 的話，第100個素還是黑色，而第101個還是白色，此時失真便會產生。

根據計算可以知道：假設白色的亮度為0，黑色為100，則第101個灰色像素的亮度應為（0*0.9）+（100*0.1）=10
這個灰色像素（10）與白色像素（0）在視覺上的肯定是有差別的，計算機圖形學稱這種由於採樣頻率不足而造成的失真為鋸齒（Aliasing）。

計算機處理像素的方法，通常是通過對某象素內的某一點進行採樣，並用得到顏色來決定整個像素的顏色（PointSampling 點採樣）。這樣的做法的確有非常高的效率，可惜代價是採樣得到的的某點的顏色無法完全體現該點所在的象素的實際顏色分佈狀況，特別是在物體邊緣，這種缺陷尤其明顯。

無論3D還是2D遊戲的物體邊緣，都會存在大量跨越著整個邊緣的像素，實際上這些像素所想表示的圖像信息（顏色）是有比例有尺寸的，符合現實情況的。但是由於點採樣技術的引入，使得邊緣處的像素沒有辦法體現出這一比例或者尺寸，在物體邊緣的整個像素裡僅僅只能顯示出邊緣兩邊的某一種顏色。對於人眼來說，這種不符合現實的邊緣間的顏色跳變是十分敏感的，為了改善這種刺眼的鋸齒，盡可能的修正像素原本應該顯示的顏色信息，於是便有了抗鋸齒（Antialiasing）技術。

從鋸齒形成的原理中可以分析推斷，抗鋸齒的方法不外乎下面幾種：
1，提高分辨率，使得像素盡可能小。
2，將跨越邊緣像素的前景色和背景色進行計算混合，用第3種顏色來填充該像素。
3，尋找一種更好的採樣方法來替換點採樣，對單個像素採用更細緻的採樣和計算。

是人都知道抗鋸齒是取材技術，爲什麽會是取樣呢。
完全就是因為馬賽克。要有這種馬賽克方塊像素樣本才能取樣抗鋸齒。
產生鋸齒是有很多因素，並非只有壓縮貼圖導致，只是當中最常見的就是壓縮馬賽克貼圖。
爲什麽一個貼圖要壓縮，爲什麽要降低質量，完全就是看主機的性能是否可以使用高質量貼圖，因為貼圖是遊戲3D的主要視覺，通常都會大量使用，如果跑不動的話就要壓縮。壓縮就會形成馬賽克。以下遊戲常見的馬賽克貼圖形成的對比。

720P壓縮馬賽克圖


使用1080P提高分辨率質量降低鋸齒




究竟誰不懂了，自己去百度吧....

沒人說過鋸齒是貼圖，而是馬賽克導致。貼圖怎麼會有鋸齒呢。寫輪眼人士別亂套話題。
當然，我說的壓縮貼圖是降低畫質，完全是爲了記憶體和處理能力，這個已經說了，怎麼被省略掉了，果然寫輪眼啊。
很簡單的，一個高質量電影，720P，在爲了記憶體同樣的720P下壓縮的意思是什麽，同樣壓縮都是指降低畫質，當然記憶體使用量就會降低，意思就是說貼圖質量壓縮的話，馬賽克就會出現，馬賽克出現就會有鋸齒。
還有，上面已經說的很清楚，並非只有貼圖馬賽克才會導致鋸齒，還有很多因素都會導致鋸齒的出現，怎麼又被省略掉了。。。呵呵
壓縮貼圖質量完全就是爲了性能，怕跑不動，原來壓縮是提高紋理的。。。果然......哈哈哈
寫輪眼看清楚我的話才回帖吧，是不是寫輪眼一目了然了。。。。吵....

很簡單的理解，隨便用一個小畫家畫一條線。
看看是不是出現鋸齒，爲什麽會出現鋸齒，因為畫格本身就是由一小個四方格像素組成，簡稱馬賽克方塊，分辨率越高，這些方格就會越小。
當然，壓縮降低畫質的畫質的話，這些馬賽克會更加明顯。
鋸齒的出現在31樓都已經有說明，像素因素都有說明。對比圖都有，看不懂的就算吧。。。吵濫交.....

哈哈，某人終於知道鋸齒怎麼形成無法解釋在發難了。。。果然.....哈哈哈
關於馬賽克鋸齒，我還有實拍圖呢，你知道什麽叫原組嗎....不過算吧，反正.....呵呵
小小的說，爲什麽4xAA會說成4個“像素”組成呢 。。。哎....一堆不x裝x吵濫交啦x

[ 本帖最后由 harry8888 于 2009-12-11 23:57 编辑 ]