August 15th, 2010
While Sony and the PlayStation 3 are doing most the pioneering work in establishing stereoscopic 3D gaming, Microsoft’s public approach has been to ignore this new dimension in gameplay, instead concentrating its resources and marketing on its Kinect motion control system.
“We’re a fully 3D-capable console today. We support 3D games that are in the market today,” Microsoft’s Aaron Greenberg told VG247.
“If you look at things like Avatar and the new Batman game, and some of the titles that were announced in 3D [at E3] like Crysis 2, they’re coming to Xbox 360. There’s no confusion that anyone looking for a 3D gaming experience will find those same experiences on the Xbox. We’re also demoing here, behind closed doors, movies in 3D running on Xbox 360. The capability is there. The question is whether or not the consumer demand is there. That’s the unanswered question. We’re not a consumer electronics company that’s trying to sell 3DTVs, so we have the benefit of waiting until the market responds. We’re going to take probably more of a pull than a push approach.”
However, behind the scenes, the platform holder is beginning to take 3D gaming seriously – something that will become very apparent within the next 12 months. Third party developers are already being briefed by Microsoft on the ways and means in which the now vintage console can be made to run with the new wave of 3DTVs. While Microsoft itself may be adopting Greenberg’s “pull rather than push” approach, it is at least offering support to publishers looking to support 3DTVs.
Ubisoft has been at the forefront of 3D, is upbeat about the take-up of the displays and foresees that many of its major titles will support the system. The new Shaun White and Ghost Recon titles are set to include stereoscopic 3D support.
“I do believe that Avatar allowed us just a little bit of advantage in terms of experience with how this market will work,” Ubisoft UK managing director Rob Cooper told MCV.
“We are working to offer the possibility of 3D on most of our upcoming triple-A titles as we’d like to ensure that we are there for those consumers that begin putting new 3D enabled televisions in their homes.”
The question is, can the Xbox 360 meet the technical standard for stereoscopic 3D set down by the HDMI 1.4 protocols, and supported by the PlayStation 3?
Real 3D – as in proper, full-on HDMI 1.4 stereoscopic 3D in the 1280×1470 twin 720p framebuffer configuration – may well be a problem for the Xbox 360. Here’s where things get complicated. In terms of the basic capabilities of the Xenos GPU, the resolution should in theory be a walk in the park. Probably the closest version of the 360’s graphics architecture on PC is ATI/AMD’s R520 (found in the X1x00 cards), capable of a maximum resolution of 2560×1600. Even its predecessor could process 2048×1536, at 75Hz, no less.
Two full 720p stereo 3D HDMI framebuffers, culled from the PlayStation 3 versions of Super Stardust HD and WipEout HD. Two images, one per eye, transmitted at 60Hz with an overall resolution of 1280×1470. It’s the standard for 720p 3D on PS3. Doubts remain as to whether the 360 can use this exact 3D format.
However, Xenos is a bespoke part made for 360 only, with its own unique properties – the 10MB daughter die of eDRAM for starters. Not only that, but all output from the GPU is routed through the HANA video processor – the chip that converts the framebuffer into HDMI, component, and legacy standard def outputs. Connect up the 360 to a DVI monitor and you can see that HANA is a pretty useful piece of kit: it’s able to support just about any single-link DVI resolution – even relatively obscure ones such as 1440×900.
However, notable by its absence is 1920×1200, the de facto standard top-end resolution for single-link DVI, and utilised by a large amount of 24″ LCDs, and from several of our developer sources, we’ve learned there’s still no support for it in the current revision of the upcoming Kinect dash, nor is there implementation of the HDMI 1.4 720p stereo 3D format when a 3DTV is attached.
Quite why it is missing is a bit of a puzzle: its omission suggests that HANA has set limitations to vertical frequency, which may preclude the 1280×1470 HDMI 1.4 set-up used by the PlayStation 3. And even if it can output the resolution, there’s no guarantee that HANA would be able to offer HDMI 1.4 handshakes to the 3DTV. After all, the chip was designed years before the HDMI 1.4 standard was even being considered.
Our developer sources inform us that Microsoft is now accepting that 3D will form a part of the Xbox 360’s future, and is recommending either side-by-side or top-bottom approaches to the visual make-up of the 3D framebuffer. The obvious conclusion is that the games we play will be operating at half-resolution, similar to the pre-alpha version of Killzone 3 seen at E3, with the image created from two 640×720 images.
Half-resolution images are something we’ve already seen with the 3D games currently available on the 360: both Blitz Games’ Invincible Tiger and Ubisoft’s far more impressive Avatar render in a user-defined choice of non-HDMI 1.4 stereo 3D techniques, but all of them are based on the principle of two distinct images crammed into one 720p framebuffer.
This then gives the PlayStation 3D solution a clear resolution advantage. The 1280×1470 framebuffer format allows for a full 720p resolution – you see it in Super Stardust HD, WipEout HD and also in the forthcoming Gran Turismo 5. However, despite these titles, there are many others which operate with resolution handicaps – Killzone 3 for example operates at half-res in its E3 guise, so while the 3D framebuffer is used, it makes no effective difference compared to a side-by-side Xbox 360 game.
(see four images in original article , “A 2D shot of Avatar (top left) followed by several 3D modes supported by the game. The one thing they all have in common is that they effectively half resolution up against the HDMI 1.4 solution.”)
A potential solution for this is to go for a 1080p framebuffer on 360: a 960×1080 image per eye actually offers more resolution than native 720p, the only disadvantage being the use of rectangular pixels, an effect we can simulate by downscaling an existing 1080p game.
Aside from question marks over whether this 1080p format is actually standards compliant with HDMI 1.4, going for a 1080p framebuffer also presents technical issues with the 360 in tiling from the 10MB of eDRAM, plus of course it introduces fill-rate issues too. More pixels need to be generated, meaning more of a load on Xenos.
All true stereoscopic 3D games face an additional challenge over and above the generation of more pixels, as Criterion’s technical director, Richard Parr told us in a discussion about the implementation of 3D in the PS3 version of Need for Speed: Hot Pursuit.
“Yes, fill rate, GPU geometry processing and RAM are the big challenges, although CPU is also a potential issue if you haven’t designed the architecture from day one to support stereo 3D – and we haven’t,” Parr says. “Fill rate and RAM can obviously be offset choosing a lower resolution, as Killzone does, but the GPU is still left needing to process twice the number of vertices. ”
In theory, the Xbox 360 should be able to match PlayStation 3’s 3D performance – when taken as a whole, the two systems are capable of remarkably similar results. However, the 360’s Xenos GPU is markedly superior to the RSX in terms of both fill-rate throughput and geometry processing. While PS3 can draw upon the performance of the SPUs to make up the deficit, the question is whether developers – particular on multi-platform titles – will make use efficient of them. This is the sort of implementation you’d really need to see added to the basic architecture of the engine, as Parr suggests.
As Ubisoft’s Rob Cooper pointed out, and it already has extensive 3D experience by retrofitting stereoscopy to its state-of-the-art Dunia engine, as used in Far Cry 2 and James Cameron’s Avatar.
“There are some special optimisations that were done for the stereoscopic version. Rendering for stereoscopy only impacts your rendering thread and GPU performance,” Ubisoft international brand manager Luc Duchaine tells us.
“As such, game logic, physics, etc, don’t need to be run twice per frame. To decrease the GPU performance hit, we are re-using the same shadow maps and we also implemented some specific optimisations. Overall, the stereoscopic version’s frame rate is close to that of the monoscopic version’s.”
This is something we can put to the test fairly easily by carrying out like-for-like tests on the game running on both PS3 and 360. In these tests the darker line signifies 2D performance, the lighter line 3D. Tear graphs for 2D are on the top of the graph, 3D on the bottom.
( See video in original article.)
On Xbox 360 the game copes well processing those additional vertices, but it’s clear to see that the same game on PS3 – already running at a performance disadvantage in 2D mode – has trouble keeping up. Bearing in mind how many game engines on cross-platform titles run smoother on Xbox 360, there is the very possibility that as 3D gains traction on multi-platform games, the 360 may well end up providing the smoother 3D experience on these titles while PS3 leads from the front with its first party output.
Other developers are planning 3D solutions that aren’t true examples of proper stereoscopy but should at least provide a decent approximation of real depth without over-taxing the capabilities of consoles that were never really designed for the kinds of workload 3D demands from what are – by today’s standards – pretty old and decrepit graphics chips.
The performance factor is something that can be mitigated and perhaps overcome by adopting a pseudo 3D approach, or 2D plus depth as it should be more accurately described. Instead of two power-sapping passes, the conventional single pass is carried out, but with separation of elements in the scene carried out based on the depth or z-buffer.