Saturday, 13 February 2010

Tech Analysis: Bioshock 2 (PS3 - 360)

Earlier this week we brought you our in-depth analysis on the technically proficient Dante’s Inferno, a game that impressed us with its startlingly solid approach to achieving almost 100% parity across both PS3 and 360, and if it weren’t for a slight horizontal blur on the 360 version, it would have been absolutely identical. Now at IQGamer we roll out the same treatment for Bioshock 2, going over every detail with a fine toothcomb seeing just how close both PS3 and 360 versions are, and of course take a look at the reasons behind any technical differences we find.

First impressions of Bioshock 2 are rather good, there initially seemed to be very little in the way of differences between both versions of the game, with texture detail being very similar and sharpness being pretty much equal. Lighting looked also to be on par for both PS3 and 360, with the only difference I noticed were with regards to the gamma levels being lower on 360, making for some loss of shadow detail in dark areas. However just a few minutes into the game things began to change, and it was extremely clear than something was going on with regards to how the effects were rendered in both versions, and the impact it was having on overall image quality.

Before I go into detail about those changes I’ll start by saying that Bioshock 2 renders in 720p (1280x720) for both platforms, with the 360 gaining an image quality advantage from having 2xMSAA (multi-sample anti-aliasing) and the PS3 version once again having no AA solution whatsoever, though a slight edge blur is present without affecting edge sharpness to any detriment. The level of sharpness with regards to the actual geometry is identical across both platforms, and this only changes when certain visual effects are present, in which case the PS3 game seems to blur noticeably over the 360 one.

In terms of texture detail and filtering, there are advantages and disadvantages on both versions to consider. These are the same ones we find on most cross platform PS3/360 ports or conversions. The 360 game seems to have a very slight edge in texture quality and detail, though not always in all circumstances. In most areas textures are actually identical across both platforms, and in other areas in which some textures seem blurrier on PS3, they are in fact the same as on 360, with the blurring caused by the lower resolution alpha and transparency effects being rendered.

In terms of texture filtering, anisotropic is present on the PS3 with 360 instead using the older trilinear method, meaning that texture detail is clearer from further away on PS3, which can lead to some of that version’s less detailed textures actually looking more detailed from a distance.

The PS3 also sees a small advantage in the area of texture streaming and with the LOD system present in the game. When playing through both versions one thing that did strike out at me was that texture pop-in was a semi-regular occurrence on 360, with on some occasions in which the higher quality mipmap would load in only a few feet away from the object you were approaching. This issue was quite infrequent and by and large didn’t affect the most prominent areas of scenery. By contrast when playing the PS3 game I noticed hardly any texture pop-in whatsoever, despite the fact that the extra level of filtering made it easier to spot any potential issues with this problem.

The reason behind this seems to stem from the fact that the PS3 game is streaming textures directly from the Hard Drive, in which there is a 5GB mandatory install, whereas the 360 is having to load them in directly from DVD. Essentially the PS3 has greater available bandwidth to do this via the HDD compared to 360’s DVD drive, which allows it to push through more higher quality textures at faster speeds, though not necessarily displaying more texture detail, as this is still limited by the system’s internal RAM.

Earlier we mentioned that there was a noticeable difference on how each version renders its transparency and alpha effects. Basically on PS3 all effects are rendered in as little as a quarter of HD resolution, whilst they are of full resolution on the 360. As we have pointed out before in our Dante’s Inferno comparison, this is done on the PS3 to save bandwidth as there is much less available than on Microsoft’s console. The PS3 only has around 21.6GBs per-second worth of bandwidth available for framebuffer effects compared to a huge 250GBs that the 360 can draw upon. This means that in order to render all the same visual details they have to be displayed at a lower resolution in order to fit into the bandwidth requirements of the PS3.

The effects of this can be seen above. Notice how the water running down the stairs is much blurrier than the surrounding stairwell and the stairs themselves. The same thing can be seen with almost all water, fire and particle effects in the game. It does mean that although textures are almost the same in both versions, the lower resolution effects tend to blur out those very same textures on the PS3. Basically the high res bump mapping and texture detail is effectively being displayed at a lower resolution and upscaled every time a transparency or alpha-based effect is rendered on top of them. With this happening frequently - as Rapture is an underwater city, leaking and slowing decaying with age - you find that the entire scene has a tendency to blur when all these visual effects are present, thus negating any advantage the PS3 version might have had with its use of better filtering and superior LOD system.

These lower res effects also feature less animation than those of the 360 game, with most of the water effects being affected, along with some rather strange errors when it came to rendering certain flame effects, and seemingly random objects in Rapture’s various rooms. Some pixallation occurs when viewing these at various angles and at long distances, and although this isn’t as apparent up close, you can still see that something doesn’t look quite right. In addition it seems that there is less, or more subtle use of bump mapping on the PS3 when compared to the 360. Sometimes it appears that the levels used are the same, at other times it seems like the PS3 is lacking in that department. Perhaps the reduced resolution alpha effects are to blame, as in areas in which there is very few of them, the bump mapping appears to be much better and can reach parity with the 360.

However there are many times when the use of lower res buffers hardly impacts upon image quality at all, looking nigh on indistinguishable from the 360 version. From what I’ve observed, this mainly applies to pools of water located on the floor in small dark corridors, or areas with low light levels. In these cases texture detail, bump mapping and IQ of the effects looked only slightly worse, and sometimes pretty much identical, showing that you don’t always need the technical advantage to produce similar results. Unfortunately this is the exception rather than the rule when talking about Bioshock 2.

You see, another issue is that these reduced resolution effects, and strangely rendered texture anomalies on the PS3 also give the game a slightly more washed out look than the 360 one. Differences in gamma between both versions we also believe attributes to this as well. The 360 game has lower gamma levels than the PS3 which means any details in really dark areas suffer from a slight black crush. Even after calibrating both consoles and the TV, the two versions couldn’t be matched up in a way that didn’t reduce the black levels of the 360 version, whilst still failing to reveal shadow detail. It’s not a massive difference, and doesn’t impact in the enjoyment of the game in any serious way, although people playing the PS3 version first will certainly notice.

Performance wise there are similar trade-offs but between smoothness and screen tearing. The PS3 version suffers from next to no screen tearing whatsoever when compared to the 360, though it does slow down more frequently in heavy battle scenes with lots going on.

Bioshock 2 runs at a near constant 30fps for most of the time, with only occasional screen tear and slow down only really occuring when lots of stuff is happening on screen at once. Occasionally I’ve noticed that the game will tear for a split second just randomly as you are venturing along Rapture’s many corridors and communal areas. Not sure why this happens, and it doesn’t seem to be performance related. The most likely candidate is triple buffering, in which the game renders several frames as a back up in case one or more of the frames are torn. It appears that occasionally the game loses one or two of its frames to tearing, and the triple buffering system accidentally displays one of those instead of a clean frame.

This however comes as a cost to the framerate, and when the PS3 game slows down it does so more frequently than the 360 one and for longer. The controls tend to suffer slightly as a result, loosing responsiveness for a brief second or two on top of the slight lag caused by the use of triple-buffering.

With the 360 game the framerate is a much steadier affair, although in response you get a greater amount of tearing. What looks to be happening isn’t always a case of a greater volume of tearing, though this does happen, and much more than you might think, but rather when the tearing occurs, it simply stays on screen a little longer than when the same thing happens on PS3. On the 360 the game also tears frequently in the overscan area of the picture, something that never occurs on PS3. Now this is an area that you simply cannot see unless you turn off the overscan option on your TV. So for 99% of people it won’t be seen at all, and naturally because of this, won’t impact in any way on your experience of the game.

In terms of performance there is no clear winner here. The PS3 drops framerate more often but has virtually no screen tear, and the 360 one doing the opposite; suffering from a greater amount of tearing but having much less in the way of slow down, making the game a smoother more responsive experience. Either way both versions present the gamer with a smooth enough engrossing experience, and the slow down on PS3 doesn’t prevent you from really enjoying the game, as it doesn’t happen very often.

In the end whilst both versions of Bioshock 2 are excellent in their own right, it is the 360 version which takes the lead, with it’s higher resolutions effects, better bump-mapping and smoother framerate, making for an all round more immersive experience. The PS3 game with its low resolution effects, although still a great game and one which looks pretty damn good at times, ventures into a slightly blurry mess on occasions when lots of water, transparencies and particles are on screen. Sadly that can be pretty often, which is a real shame as these effects are integral to helping create Bioshock’s wondrous and foreboding atmosphere.

Either way if you only have a PS3 don’t be discouraged, as many of the issues seen here are not always apparent, plus you get next to no screen tearing and a still very good looking game (in many places at least), just not as technically accomplished one.

Overall if you have both systems and given the choice, I’d say that the 360 game is the one to get.

If of course you've had enough of reading about all this tech stuff, or simply looked at those pictures instead, head on over to Beames on Games for the full review of Bioshock 2.

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