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Tech Focus: Motorstorm Apocalypse

From first impressions of the PS3 to stereoscopic 3D and 1080p

Digital FoundryIt's not been mentioned much in the marketing, but MotorStorm Apocalypse supports 1080p to the same level that Gran Turismo 5 does - native 1280x1080, upscaled to full 1080p. Bearing in mind the increased fill-rate requirements of 3D, did 1080p support come about almost like a by-product of supporting stereoscopy?
Oli Wright

Yes. If we stayed at 1280x720 for 2D, it would inevitably mean a compromised 3D experience. We saw it as an opportunity to improve our 2D experience though. This is a gross oversimplification, but 1280x1080 is exactly the same number of pixels as 960x720x2 - so that's what we targeted, although in the end it became 1024x720x2 due to some boring alignment reasons. Of course we also wanted to add dynamic lighting, improve our shadows, fix our particle halos, add MLAA and add SSAO. It goes without saying that we're not sane.

We'd rather have a four-player experience with some compromises than not have it at all.

Oli Wright, lead graphics programmer, Evolution Studios
Digital FoundryYou've worked extensively in retrofitting 3D to Motorstorm: Pacific Rift, using techniques such as lower detail models and dynamic resolution - how valuable was this work in the new game and do you have use any of these techniques in Apocalypse?
Oli Wright

With a game like Apocalypse, it's incredibly difficult to guarantee the RSX rendering time for any given frame up-front. The frames are just so variable, primarily because of the vehicles. We like to have lots of vehicles on screen, and often they're close to the camera, and quite often engulfed in a fireball. So we have two choices. We either make everything so cheap that we can draw our most expensive frame still within budget, or we scale back the rendering for frames that we think are going to be over budget.

We hugely prefer this latter approach. It means the RSX is close to being maxed out far more often, without losing frames. If we didn't do the dynamic detail scaling, then it would mean that the RSX would be idle for a lot of the time to give us the headroom for our variable frame cost, and frames that were more expensive than we considered for would tear and frame out.

Digital FoundryDo you use dynamic resolution in the 2D 1080p mode? On a more general level, resolution adjustment on the fly suggests that you would need to anticipate bottlenecks and spikes before they actually happen - what is the real-life approach?
Oli Wright

We do use dynamic resolution changing in 2D - but we've tried to budget things so it only kicks in in exceptional circumstances. When you play the game, it's really hard to notice it happening unless you have a little flashing light that pops up to say 'dynamic resolution active!' Our rule for anticipating the RSX rendering time is simply to assume that the current frame will cost the same as the previous one, unless there's a camera cut. It's a bit basic, but it works very well.

Digital FoundrySplit-screen support has been upped to four players for Apocalypse, including online integration. What were the major rendering challenges here and how did you overcome them?
Oli Wright

Split-screen is, obviously, a nightmare. We have lots of things that we can scale back to make four-player split screen possible. LOD biasing, shadow resolution, shadow range, SSAO and motion blur. So the visuals are compromised in four-player, but we'd rather have a four-player experience with some compromises than not have it at all.

Digital FoundryOnline integration of split-screen gameplay suggests that the amount of raw data you need to transmit over the internet increases exponentially with each new player you add - are there any implications here for latency?
Dave Hewitt

If you have a peer-to-peer architecture then yes, there will be an exponential increase, and you do run the risk of saturating the upstream bandwidth on a consumer connection, and introducing latency. However, since we have a client/server architecture there is no exponential increase in network traffic - only a linear increase in upload.

MotorStorm Apocalypse's support for 3D means gains for 2D players too - there's processing power for the game left over to support 1080p, with 1280x1080 native res upscaled to full HD. A similar approach is used in Polyphony Digital's Gran Turismo 5.
Digital FoundryThe basic principle of off-loading GPU work onto Cell seems to be a common approach in all the major Sony first party titles - does the same principle hold true for Apocalypse? What are the major tasks in the rendering pipeline you assign to the CPU and RSX?
Oli Wright

The only major pixel-pushing task that we run on SPU is the MLAA. The SPUs are mostly occupied with physics, vehicle simulation (which runs at 600Hz), animation processing, particles, scene processing and rendering preparation. They're certainly not sat idle. If the SPUs were tied up doing lots of work off-loaded from the GPU, then we'd need to have much simpler worlds with far fewer dynamic objects. That wouldn't be MotorStorm. As it stands, we have worlds with over 2000 dynamic objects in them.

Digital FoundryFrom what we've heard of ATG's MLAA, the technique is designed for a 1280x720 framebuffer, but you have it running while processing 50 per cent more pixels in 1080p mode. Did the MLAA tech require an upgrade? What was involved here?
Oli Wright

The MLAA processing itself wasn't upgraded, it just took 50 per cent longer to run. So we had to find the SPU time and the XDR memory to make it work.

Digital FoundryA smooth, consistent frame-rate and controller response is especially important in a racing game - what are the systems you have in place for maintaining performance? Do you use anything along similar lines to Guerrilla's Autobot?
Oli Wright

We have a couple of tools to try to make sure that the performance of world rendering in particular is as consistent as possible. The first is a world benchmarking tool that runs a camera through the world along all possible routes, timing various GPU phases and reporting on hot and cold spots. The second is a tool called The Auditor that gives a more spreadsheet type breakdown of a resource usage for a world.

Digital FoundryOn a more general level, you've now shipped three major PlayStation 3 titles, each significantly different to the last. Do you feel that your tech has matured, or are there any specific areas you still feel could be better exploited?
Oli Wright

I don't think we'd ever be complacent enough to say that any particular area can't be improved upon. There are always things that can be done better. A major area for us that we know we need to improve on is that of world production - our existing process is simply too labour intensive.

In terms of exploiting the hardware better - yes - there are always things you have in your mind that could be done better. But there's always a difficult balance to strike between making something that's production ready versus blue sky experimentation.

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Richard Leadbetter avatar
Richard Leadbetter: Rich has been a games journalist since the days of 16-bit and specialises in technical analysis. He's commonly known around Eurogamer as the Blacksmith of the Future.