Not so High Definition

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.

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.