Sunday, 14 November 2010

Tech Analysis: Call Of Duty: Black Ops (360 vs PS3)

It’s no surprise to hear that the Call Of Duty series currently leads the way in high-precision first-person shooters, with low latency controls and a framerate to die for, where near instant feedback and overall fluidity makes it one of the best gaming experiences around. And all of this comes with the decision to aim, and achieve a blistering sixty frames per-second. The sheer advantage that this bump in smoothness provides cannot be underestimated, and seeing this on primarily a console release is outstanding to say the least.

Of course, with such a high level of fluidity to maintain (something that is utterly essential for the whole experience to work) some compromises have obviously been made. And to that end, sacrifices in overall rendering resolution have taken place in order to accommodate this, along with reduced lighting and shader effects compared to other comparable games.

But despite this, the series is still home to lavish visual spectacle: a myriad of particle effects often don the screen, and a whole lot of work has gone into creating a highly detailed, albeit often closed off world in which to best demonstrate the trade-off between all out graphical exposition and a blindingly smooth framerate.

And with Call Of Duty: Black Ops, the action is even more intense, the effects are even more spic in scale, so parity between platforms then isn’t quite on the same level as with MW2 - compromises have definitely been made in getting the game up and running on the PS3 without cutting back on the core assets used. Though when you consider the additional graphical upgrades the engine has seen, the differences, compromises, whatever you want to call them, are completely understandable, if not unavoidable.

Like with previous instalments, the engine powering Black Ops is clearly engineered around reaching and maintaining regular 60fps performance. And like with those titles, it is no surprise to find that the game is presented in sub-HD on both platforms, with the drop in resolution offset with good scaling and use of anti-aliasing, following the same blueprint as every other COD title.

Black Ops renders in the familiar 1040x608 resolution on the 360, while the PS3 build gets a further downgrade to the even more lowly 960x544. Both versions benefit from having 2x multisampling anti-aliasing (MSAA) help smooth over the upscaling process, reducing jagged edges at the same time.

The change in rendering resolution on the PS3 may at first seem a little surprising. But Black Ops has also had some noticeable upgrades in shader effects and in its use of alpha-based particles, both of which put a heavier strain on the engine than ever before. In essence, getting better performance with more in the way of effects means sacrificing the overall pixel workload - something PS3 owners aren’t exactly unfamiliar too.

Looking at the screenshot above, you can easily see that the 360 game commands a slight, but noticeable lead in sharpness. The reduction in both horizontal and vertical resolution clearly impacts on overall image quality, resulting in a slightly blurrier look, and fuzzy edges being present on far-away objects. However, in motion the two look far more alike, and from some 5 feet away on a 32” screen, the PS3 game only looks slightly softer. The quality of the scaling is still incredibly good, and compared to the PC version you can see that both PS3 and 360 builds are fairly close to each other.

Despite the sub-HD nature of the framebuffer, Black Ops still looks relatively clean and reasonably sharp as a whole in motion. While many have stated that the game looks worse in this regard than MW2, this is actually down to Treyarch’s dark and gritty art style more than the technical make-up of the game itself. The clinical nature of Inifinity Ward’s own art is replaced with something partially more organic, rougher in appearance. On the 360 build the actual resolution, and most of the underlying tech is presented in the same way, bar the obvious improvements.

As already mentioned, the use of MSAA helps in mitigating intrusive upsclaing artefacts, whilst the edge smoothing it provides deals with most jaggies fairly effectively. There is still some shimmering that occurs in the trees and surrounding foliage in many environments - naturally thin stripes of geometry, such as fences and powerlines are affected, suffering from sub-pixel aliasing. Although, this is nothing to be overly concerned about.

Thankfully, much of the game remains almost like for like in most areas. As with MW2, texture detail for example, is pretty much identical across the board, with only a few genuinely lower res textures appearing on the PS3.

Most of the differences apparent in screenshots actually stem from a texture streaming issue on the PS3, whereby mip-map transitions are a little behind. The actual assets used are for the most part, identical, with only a few lower res textures to be found here and there in places. You can clearly see this when both versions are running side by side, where these texture transitions are also visible on the 360, but not quite so often.

On the other hand, in terms of texture filtering, we can see that the 360 build features slightly better AF (anisontropic filtering) at all times, in keeping with the change introduced in MW2.

Previously, on past COD titles it was the PS3 versions that always had a filtering advantage owing to the RSX GPU having more texturing units than 360’s Xenos. Effectively, this meant that high levels of AF were virtually free on Sony’s system. Whereas on 360 similar quality was only obtainable by using a combination of AF plus a bilinear or trilinear solution. This is now reversed in Black Ops, as it was in MW2. And as a result detail is indeed visible for further into the distance on the 360.

The use of sub-HD framebuffers has always been a staple for the COD series on consoles, and the new texture streaming tech introduced in MW2 clearly helps both versions maintain a similar level of high quality artwork throughout. However, in terms of particle and alpha effects the 360 usually sees a near continuous advantage. The exception of course was with Modern Warfare 2, which was the first game in the series to even things up with equal size buffers across both platforms.

Looking at Black Ops, and things seem to have taken a step back. The increase in smoke, particles, and fire effects all eat into each systems available bandwidth, and with the PS3 having less of that particular resource available, it means that a few cut backs have been made in order to sustain overall performance.

On the PS3 all these effects are rendered in a lower resolution to the rest of the frame. Whereas on the other hand, 360 owners get the same level of graphical fidelity on these objects as seen in past COD titles – full res buffers. The differences can be seen above for those interested: you can clearly see that the effects look softer and less defined in the PS3 game due their resolution being reduced.

Of course this is a common trade-off for owners of many AAA PS3 titles. Rather than sacrificing the amount of objects being rendered on-screen, developers usually choose to either: render certain objects in a lower resolution to the rest of the frame, or to render them in a half-resolution of sorts using A2C for blending, introducing shimmery screen-door artefacts into the mix.

For Black Ops it is the former we are seeing, and the choice made in terms of preserving quality was definitely the right one. The developers have taken the time to carefully blend all alpha effects in the PS3 game order to ensure that as little shimmering or aliasing takes place as possible. Aside from the odd bit of pixelation, in motion (at regular viewing distances) these differences are likely to go un-noticed for many people.

Looking at performance, when it comes to a Call Of Duty game, maintaining 60fps is absolutely paramount, and the sacrifices made with regards to both the overall framebuffer, and the use of lower res alpha effects are an essential part of trying to achieve that goal.

In effect, without that 60fps update COD would be just another arcadey military shooter with large set pieces, and the tendency to rip-off various action movies/famous war flicks. So, it goes without saying that the reduced resolution on both platforms, and lower res effects on the PS3 are a worthy trade-off in meeting that goal.

To that end, on the 360 Black Ops manages to largely hit its target 60fps for much of the time, but with frequent drops throughout the entire single-player campaign. Most of these drops are so subtle in nature, that you may not notice them. And even when the game noticeably approaches framerates in the 30-40fps mark, the action always seems smooth and incredibly fluid.

Controller latency does indeed increase slightly, but not to detrimental levels – the action always feels smooth even when the framerate is noticeably running below the desired 60fps.

In terms of the larger framerate drops, they tend to occur in scenes with high levels of environmental detail, or when there is heavy use of alpha going on. In these kinds of scenarios the game regularly drops down well below the 60fps mark, though it maintains for the most part, an update above that of the more common 30fps.

Moving on to the PS3, and we can see the same trend occurring through the first few levels. Black Ops starts off confidently, running at the targeted 60fps with relative ease, although this begins to drop considerably in areas with more detail putting a greater load on system resources. In almost like for like scenarios the PS3 game perhaps lingers behind by around 10 to 20fps or so, in a rough estimation of what I am seeing.

Outside of the gameplay, and things are even more pronounced - during cut-scenes the 360 game runs at a near constant 60fps, with very little slowdown whatsoever. On PS3 however, the framerate has a tendency to drop regularly, but not always in a smooth fashion – the cut scenes often stutter, almost like the game’s framerate was bouncing up and down in small increments.

Despite the differences in performance during gameplay, both versions end up feeling smooth and extremely fluid, just with the 360 game commanding a noticeable lead on many occasions. The PS3 version, even during times of slow down, still feels very responsive, and the drops down to 30fps aren’t quite as bad as they sound. However, neither version manages to lock down a constant 60fps, with regular dips happening according to the action on screen. In this respect MW2 is clearly superior in this regard.

On the plus side both versions are solidly v-synced and exhibit no screen tearing of any kind, which is in itself impressive, if not another trademark of the series highly optimised 60fps game engine.

Outside of performance, and we can see that the overall rendering engine has seen some considerable upgrades for Black Ops. Most noticeably there is an increase in use of dynamic lighting and shadowing, first expanded upon greatly in MW2, and the use of better surface shaders on the characters. Normal mapping also looks to have been refined slightly as well.

Dynamic lighting and shadowing is now more abundant on both versions. Gunfire, explosions, and fire etc, light up the surrounding environment to a larger degree than before, whilst use of dynamic, and self-shadowing creates a greater level of depth to the scene. Examples can be found all through the game - the fan in the bar at the beginning, and the rotating emergency lights on the ceiling in another mission showcase these improvements early on, whilst the second Vietnam stage (set in the jungle and caves) demonstrates this effortlessly.

In terms of shadowing, the 360 build benefits from not only high-resolution shadows, but also better shadow filtering as well. By contrast shadows are rendered in a lower resolution on the PS3, often looking rather blurry, and occasionally quite pixelated. Like with the use of lower resolution particle and alpha effects, the reduction in shadow quality has been done to save on memory bandwidth, thus allowing the full range of graphical improvements to be included without cutting back on their scope and visual range.

The only exception to this appears to be with the amount of bloom lighting on screen. Bloom has been paired back on both versions from earlier COD titles, and in Black Ops the effect has been even more reduced on the PS3. However, this appears to be more down to gamma and contrast differences between both versions. Although, even when adjusting the in-game brightness slider, and the brightness control on my calibrated HDTV, I still wasn’t able to get a complete like for like match.

This gamma/brightness issue made the PS3 version of the game appear slightly more washed out than the 360 version. It seems that even when calibrtation to both the game's brightness and the HDTV settings have taken place, overall contrast is still reduced on the PS3.

Other than that, both versions are largely like for like in pretty much every other area. Resolution aside there’s very little that has been actively cut back on, instead the developers have preferred to render in a lower resolution on PS3 and maintain the amount of visual spectacle seen in the 360 build.

In terms of multi-platform development, achieving parity on both platforms whilst pushing the tech forwards even further on, Treyarch’s effort here is indeed commendable despite not reaching IW’s high point with MW2. The engine itself has seen a number of carefully implemented, and thoroughly skilled deployments, from an obvious increase in the use of dynamic lighting and shadowing, to the presence of more advanced skin shaders and overall character modelling. The tech is solid, as it is impressive.

Perhaps the only thing which doesn’t have the same level of impact, is with regards to the overall quality of the PS3 version of the game, which does indeed suffer from the traditional lowering of FB resolution and alpha effects buffers. That said, ‘suffering’ is maybe too strong a word to use, as whatever such improvements were implemented, every one of those are stretching memory requirements on both systems – it just so happens that overall memory constraints (especially bandwidth) is simply more of an issue for PS3 development in general.

But for a game that is so doggedly built around 360’s high bandwidth, fast EDRAM, to see pretty much all of the improvements on the PS3, even if they are in a lower resolution is an impressive feat nonetheless. The reduced screen resolution is one thing that does disappoint – it is indeed noticeable. And the framerate, which has taken a bigger hit than before, could be substantially better.

That said, Black Ops is still well worth picking up on the PS3, and for many, most of the graphical differences will absolutely fail to register. If you have access to both platforms however, then there is no contest: the 360 version, with its higher resolution FB and effects, smoother framerate and sharper image is the one to get.

In conclusion, Call of Duty: Black Ops is a worthy combination of graphical compromises interwoven with impressive underlying tech, that which, for the most part comes out shining incredibly well as a whole. Given the make-up of the engine, and the load being pushed on screen, I couldn’t have seen it going any other way with regards to platform parity. But at least the end result is overly solid and well balanced - the baseline tech and assets haven’t been cut back on.

As ever thanks go out to AlStrong for counting those pixels, and to for the screens.

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