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The Making of Shift 2 Unleashed

How to pull a double shift.

While MLAA is now an important component in Sony's performance-enhancing Edge tools, the development schedule required that Slightly Mad utilised a pre-release version of the tech.

"It's a slightly modified version of the pre-release Edge code. It's very easy to integrate in the pipeline and is placed between the HDR tone-mapping phase and motion blur," clarifies PS3 lead Tim Mann.

"It can be quite fussy tuning-wise but we managed to find a good balance between too much edge-detection - which produces too much blurring - and not enough, which leaves you with jagged edges."

Slightly Mad uses individual teams to produce each version of Shift 2, an acknowledgement that while the feature-set is identical between platforms, the ways and means by which this was achieved required addressing each console individually.

"We basically looked at what the required output was - be it damage, motion blur, HDR etc, and then at the initial source data for that stage," adds Mann.

"How we then got from one to the other was left to the platform-specific teams since, due to using completely different techniques on each platform, certain things took longer to process on one than the other. Damage, for example, is a breeze on an SPU but takes longer on a 360 core.

"On the other hand, the 360 has a much quicker GPU in general, so some graphical items had to be processed on SPU on PS3. We didn't really impose any restrictions on the techniques that could be used, be it SPUs on PS3 or threads on 360 - just use what you have available."

A breakdown of the different rendering passes used to create the frame in the centre - an interesting insight into how a deferred frame is broken down into individual buffers which are then combined for the final image.

Common to all three versions of the game is a move to deferred rendering, a technique utilised in many of the most advanced console titles on the market. Slightly Mad went for the light pre-pass approach, as used in titles such as GTA IV, Medal of Honor and Blur.

"We use a three-phase light pre-pass approach for our deferred renderer. The main reason we chose this as opposed to a two-phase approach was because being a racing game, we needed to focus on high-quality rendering of diverse material types, ranging from rubber and cloth all the way up to paintwork, glass and carbon fibre," reveals Nettleship.

"Also, our most important visual components are the cars, which need high-quality environment mapping. We tried every encoding possible for the normals channel of the G-buffer before deciding that it wasn't possible to get an acceptable quality level for bodywork reflections. So, we dropped back to the cheapest normal encoding (888 view space XYZ, which helped a lot with PS3 performance) and use those for general lighting. For bodywork reflections, we re-evaluate the normal mapping in the third phase of the light pre-pass render. It's more expensive, but the quality you get makes it worthwhile."

This isn't technology being implemented for its own sake, it's the application of an advanced rendering technique with results that go beyond better-looking cars or more aesthetically pleasing lighting. The shift to a deferred approach produces a distinct look and feel that adds to the core gameplay experience.

"Lighting is one thing - talented artists can easily recreate a stunning sunset or a starry sky, but with the advanced techniques our engine is capable of we've now been able to temporarily blind the player with dazzling sunlight as they approach a corner or cast individual shadows across their dashboard when racing at night," enthuses design lead Andy Tudor.

"Not only do these effects look spectacular but they also invoke an emotional reaction from the player; concentration when approaching a tough corner, fear when descending into the pitch black darkness, or apprehension seeing the headlights of a car behind sweeping across your dashboard knowing that one wrong mistake and they're going to overtake. So lighting in Shift 2 Unleashed is an integral part of heightening the challenge when racing, not just making the environments look pretty."

Having additional control over the lighting of the game also ensures an additional level of individuality in the game's many environments.

"With 100 different track locations in the game spanning 15 different countries we also wanted to make sure they were both distinguishable and true to their geography for easy recall by the player," Tudor adds.

"Regardless of track layout, the sun and 'temperature' of the West Coast Willow Springs track therefore intentionally looks distinctive to that of the East Coast Laguna Seca, despite sharing common geological traits such as ground composition and vegetation. As you play through Career, a forest-based Belgian track immediately followed by a forest-based Italian track will look different to each other and ensure individuality and variety."

Image quality between the Xbox 360 and PlayStation 3 versions of Shift 2 is very close indeed, the only obvious difference being 4x MSAA on 360 and SPU-based MLAA on the Sony platform. Use the full-screen button for 720p resolution or click the link below for a larger window.

Bearing in mind the overhauled engine, Slightly Mad handed in a sequel that operates at the same consistent 30 frames per second as its predecessor. Dynamic adjustments to elements such as LOD (level of detail) help make this possible. The studio's approach is that consistent gameplay is as important as the visual make-up of the game.

"We take the view that both graphical and gameplay quality are critical to the experience of our games so we throw everything possible in, and then optimise via a range of in-house tools," explains render lead Rob Dibley.

"I don't think there was ever a silver bullet. Every area was optimised individually. We used a number of approaches including controlling level of detail on light shaders, clipping light cones to geometry, running large chunks of the rendering logic on SPU on PS3, dynamically prioritising shadows based on light occlusion tests, MLAA instead of MSAA on PS3 etc."

A lot of clever behind-the-scenes logic is used to assess how much stress the action puts on the engine, with the game allocating rendering resources in order to produce the best possible look.

"Asset-wise, we profile the render cost of each vehicle (and each upgrade thereof) in a fixed scene in order to determine which vehicles need to be modified for performance and similarly we profile each track location using an automated camera system that moves around the track monitoring performance and identifying hotspots for optimisation," Dibley continues.

"We also use dynamic variation of detail in order to keep the performance up when it starts to drop due to a heavy load from some particular situation. In the same way that MP3 compression removes subtle detail from audio to compress it, we analyse the entire frame context and if there is a lot of foreground detail you won't miss background subtleties. In the same way that if you are driving very slowly you notice a lot more detail."

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About the Author

Richard Leadbetter avatar

Richard Leadbetter

Technology Editor, Digital Foundry

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.


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