Digital Foundry's shock of the week: Tekken 6, one of the most anticipated fighting games of the year, has an ugly secret. Blocky, blurred and clearly upscaled, it is the latest example of the "not so high definition" generation: games designed for HD consoles that fall short of the visual quality we should be expecting from our hardware.
The rumours surrounding Namco's flagship fighting game - going cross-platform for the first time - have been floating around tech forums for the last couple of weeks, based on screenshots from various sources, none of them conclusive. Analysis of Xbox 360 screens released to date reveals native resolutions of anything from 1280x720, to 1360x768 to full-on 1080p. On the other hand, PS3 assets released so far reveal a disappointing 1024x576 resolution - over 33 per cent of the 720p detail gone, just like that.
The disparity between the available Xbox 360 shots was enough for Digital Foundry to suspect that something was clearly amiss, and based on the preview code we have available, direct HDMI dumps reveal a 1024x576 framebuffer on default settings. All of which sounds like another cross-format catastrophe, but the reality is somewhat more intriguing and, at the same time, rather bizarre.
On a more general level, controversy has surrounded the issue of sub-HD gaming since around the time the Xbox 360 actually launched, but some eagle-eyed journos were quick to notice that something wasn't quite right even before the console hit the streets. Working on the UK's Official Xbox Magazine at the time, UK: Resistance writer Gary Cutlack was probably the first to realise that something was amiss. Way before the online press caught on, Cutlack had figured out that the HD revolution hadn't quite begun quite yet.
"I first noticed it while reviewing launch game Project Gotham Racing 3 a few weeks prior to the console's release," Cutlack told me. "The Xbox 360 debug grabbing software - which dumps images onto a PC direct from the console's memory as you well know - was leaving me with in-game screen grabs at 1024x600, while the menu screens were the proper 1280x720. 'That's not quite the 720p Microsoft has been endlessly banging on about,' I remarked, probably to myself then to you in an email. Little did I realise this was a downsizing output scandal that could've generated sizeable Internet traffic had I 'gone public' with it. Numerous games did it in the early days - including pretty much everything from Activision."
In short, the tools supplied by Microsoft itself to games journalists gave writers the ability to get a direct dump of the Xbox 360's framebuffer, in its original format. Simply by looking at the resulting file's dimensions, you got an accurate reading of the game's actual resolution before the scaler in the Xenos GPU got to grips with upscaling the image to proper 720p. Project Gotham Racing 3 came in at a disappointing 1024x600. Perfect Dark Zero measured up at 1152x640. Tony Hawk's Project 8 achieved a measely 1040x585.
At the time, Microsoft's TRCs (the Technical Requirement Checklist) could have effectively put all of these games back to the drawing board. Pre-launch, Microsoft had promised that native 720p would be minimum, and that 2x multisampling anti-aliasing - used to smooth off jagged edges - would be mandatory. These requirements were put on hold during the launch period simply due to the fact that the game-makers only had final silicon for a few months before the system launched. Prior to that, G4 Macs with ATI graphics cards were used to emulate the console. One rumour has it that Need for Speed: Most Wanted ran on an overclocked version of this set-up for its debut on "360" at the 2005 E3.
As development on the console gathered pace, Microsoft's resolution and AA requirements seemed to relax still further, up until the point where recently, Black Rock Studios' David Jefferies interpreted his NDA somewhat differently to most other 360 coders and revealed that Microsoft had dropped these particular TRCs completely.
"We are making a trade-off and saying that the screen resolution is more important to us than the quality of the anti-aliasing," Jefferies told Develop magazine. "This isn't necessarily an entirely voluntary move because, until recently, Microsoft had a TCR insisting that games run at 1280×720 - providing you weren't one of the lucky ones like Halo, who got it waived and ran at 1152×640, that is."
So what's the score with sub-HD gaming on Xbox 360? Why can't we have full 720p and 4xMSAA, as seen on very clean-looking games like DiRT 2 or Fight Night Round 4? The answer, ironically, is all down to one of the architecture's greatest strengths. The Xenos GPU is able to achieve massive throughput due to the fact that 10 megabytes of so-called eDRAM is attached directly to the graphics core. An effectively infinite level of bandwidth is available to cope with "expensive" effects such as transparent (alpha) textures and of course anti-aliasing. It's one of the key reasons why Xbox 360 cross-format titles often have a graphical edge over the PS3 versions.
Unfortunately, that 10MB limit is the 360's Achilles heel. It's enough to contain a 720p image, but with no anti-aliasing. To incorporate 2x anti-aliasing simultaneously, resolution needs to drop to the 1024x600 or thereabouts seen in titles like Call of Duty 4: Modern Warfare, Project Gotham Racing 3 or Oblivion. If you want to go higher, a process called tiling kicks in, where the framebuffer is split into chunks and swapped out into normal memory, impacting performance. Geometry that spans tiles has to processed twice, or even three times. Some developer estimates put the cost of using two tiles (enough for 720p, 2xMSAA) at around 1.4 times the level of keeping everything in the eDRAM. Three tiles, as used for a 720p, 4xMSAA image, or a non-AA 1080p framebuffer, up that requirement to 1.6 times the overhead.
Capcom's Framework MT technology, as used in most of its Japanese titles from Lost Planet through to Resident Evil 5, adopts an interesting - and unique - solution. By default, it uses the three tiles for a maximum quality 720p, 4xMSAA framebuffer. However, when the engine needs that extra level of performance, it'll drop down to using two tiles (2x) or even no tiling at all (no AA). To put things more simply, Capcom adapts its engine dynamically, and very well too - it's extremely unlikely that in a truly action-packed scene that the gamers will notice "teh jaggies".
In short, the processing cost of tiling can seem prohibitive to some developers, so they either lower the resolution, or in the case of Black Rock Studios' game, they drop the anti-aliasing completely. Often, computationally less expensive effects like blurring are added instead which rarely helps overall image quality, hence the term coined by Eurogamer editor Tom Bramwell: the Vaseline effect. [Not sure I invented this, but I'll take it. - Ed]
The advent of Halo 3 brought the whole sub-HD issue back to prominence when it was discovered that Microsoft's key tentpole title of 2007 was in fact in contravention of its own technical requirements for game developers. By this time, the journalist screenshot trick no longer worked. Developers were internally scaling their lower-res framebuffers back up to 720p, then overlaying text and HUD data at proper HD resolutions before supplying the result to the video output - Halo 3 is a case in point. Text and HUD detail looks terrible upscaled, so this technique ensures readability of key information without requiring the whole framebuffer to be rendered at 720p. Curiously, Microsoft itself patched the screenshot code in their own tools too, so that even older games like PGR3 still output 720p shots.
Halo 3's resolution was the subject of discussion before the game launched, back during E3 2007, when Beyond3D forum member one first noticed that the game literally looked a little rough around the edges, but actual methodology in confirming this was non-existent. Enter the enigmatic Beyond 3D forum contributor, Quaz51, who came up with the idea of pixel counting - the idea of comparing the ratio of in-game pixels to display pixels, and working out the true resolution by comparing the difference. His contributions when the game was actually released ensured that there was a scientific method in place for measure real game pixel levels.
So, Halo 3 was outed as running at 640p, clearly annoying Bungie, and the same measurement technique was soon deployed on a range of games that were running at significantly lower resolutions than was previously imagined. We also started to see the disparity between cross-platform games in a much more scientific light. For example, Starbreeze Studios' The Darkness got full 720p visuals on Xbox 360, but a paltry 960x540 on PS3 - not good, especially in light of other cutbacks in texture detail and lighting. Beyond3D has a comprehensive list of game resolutions, regularly updated, and is pretty much the definitive resource for Xbox 360 and PS3 games.
In the case of Halo 3, and its pseudo-sequel ODST, Bungie's decision to opt for HDR lighting meant that the Xbox 360's memory deficit in the eDRAM was once again the prime suspect for the performance issues. Similar to conventional HDR photography, the final image you see is actually based on two passes of the scene using different dynamic ranges and those two passes were thought to have issues fitting into the available 10MB eDRAM. However, Trials HD uses similar HDR techniques, with only a minor hit to resolution, carefully hidden away in the average HDTV's overscan area at the top and bottom of the screen.
In effect, the eDRAM limitation means that Halo could have been 1280x680 like Trials HD (with 20 pixel borders top and bottom) or instead 1208x720 [sic]. That being the case, the reduction seen in Halo 3 is almost certainly down to the need to maintain the 30FPS frame-rate, which the game manages to achieve very well indeed (at least according to our own analysis of the single-player campaign).
We suspect that fill-rate and pixel shading are the main issues in maintaining Halo 3 performance and it's here that we see much the same reasons why a selection of PlayStation 3 cross-platform games run at a lower resolution compared to their Xbox 360 counterparts.
Fewer pixels to render means less stress on the fill-rate (the process of filling in the millions of triangles from which the screen is created), and obviously the shading effort require for those pixels is reduced significantly, as there are literally fewer of them to process. Over and above those factors, PlayStation 3 bandwidth to the GPU is often cited by developers as a reason why working with RSX can be challenging - while the graphics hardware is equivalent to an NVIDIA G71 chip like the 7800GTX, it only has a 128-bit bus to communicate with the rest of the architecture. In short, it's often the case that information to and from the GPU to Cell is held up due to the size of the pipe connecting them.
So, in the case of a game as anticipated as Tekken 6, is there no hope that the game might actually run at proper 720p? We only have preview code, right? What about optimisation? Well, short of the developers completely binning off a lot of the work on their current engine (which we suspect is derived from the Soul Calibur IV code), it's unlikely that the core rendering techniques will change that dramatically when the game finally ships. If it does, we'll be sure to tell you.
But here's where things get very, very weird. Indeed, Tekken 6 is the most bizarre game we've ever analysed in that with just one option tweak you can get the game running in excess of 1280x720, on Xbox 360 at least.
The reason that 1024x576 resolution has been introduced is to accommodate the dynamic motion blur system that Namco-Bandai has added to the game. Similar to Killzone 2 and Uncharted 2, this effect is realistically calculated in order to produce the effect of motion smoother than the actual frame-rate. It actually works rather well, and the developers have added code that makes the game arguably look superior in some respects to the higher resolution mode.
Simply turn off the motion blur effect and resolution jumps from 1024x576 to 1365x768 (the same as Soul Calibur IV). In effect, resolution almost doubles, in exchange for the omission of motion blur. However, there's still no anti-aliasing, so overall appearance still looks pretty rough compared to Street Fighter IV and Virtua Fighter 5.
Regardless, it's quite a remarkable turn of events, and the first time we've seen anything like it. But the staggering thing is that in this case, the extra resolution does virtually nothing for image quality. Check out this comparison, with analysis from DF contributor MazingerDUDE. Texture detail on the sub-HD image is noticeably sharper than it is in the higher-resolution image.
Pixel measurements for Tekken 6 on Xbox 360 with blur on, and blur off. Switch between the two shots, and note the difference in detail on Heihachi's pantaloons. Despite having almost twice as much resolution, 576p looks sharper.
So, what's going on? We'll be producing a more in-depth report once we've taken a closer look at the PlayStation 3 version of Tekken 6, but in the case of the Xbox 360 version, the reduction in resolution is also backed by additional processing of the texture quality. So in choosing between the two options, you're effectively selecting fewer jaggies (768p) instead of nice motion blurring, and higher quality, sharper textures (576p).
The end result is that the two modes look much the same in motion, and from a personal perspective, neither of them look that attractive overall. However, Namco-Bandai's approach is an intriguing one in that it suggests that working with a lower resolution doesn't necessarily mean that it's automatically the wrong choice for the best look overall. But certainly, it is the first and only game we've seen where the additional processing does make up for, and indeed sometimes surpass, the resolution deficit in terms of actual detail.
While custom solutions like this may well appeal to the geeks in us, the fact remains that in most cases the traditional solution of working at native resolution with edge-smoothing anti-aliasing employed does produce the most pleasing image quality. However, the recent changes at Microsoft now mean that both HD platform holders are giving the developers the freedom to do as they will. We can only hope that it doesn't open the doors for more games with sloppy code making their way to gamers. Interesting technical trickery as seen in Tekken 6 is one thing, but the overwhelming use of sub-HD resolution is in making code that can't run at a sustained frame-rate at 720p run acceptably smooth.
In the meantime, keep your eyes peeled for a more in-depth Tekken 6 update coming in the next couple of days. While our analysis has been limited to the Xbox 360 version of the game, it has to be noted that Tekken 6 is an arcade game running on PlayStation 3 hardware. Will this translate into higher performance on the Sony platform? Digital Foundry will have the definitive answers.
http://www.eurogamer.net/articles/digitalfoundry-not-so-high-definition-article?page=1
