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Killzone 2 Breakdown: Part Two

Also: What is deferred rendering?

Into the second part of our Killzone 2 coverage, and with it, analysis of three more campaigns, plus a primer on Deferred Rendering - the key technology that runs the game's engine.

Deferred Rendering generally applies to the deferring of some aspect of rendering, whether it be lighting, shadowing, shading, or other, writes Alex Goh. For a deferred lighting renderer, the entire frame is broken down into several render targets/frame buffers that each describe particular surface properties in the scene and are then combined (or used in other post-processing effects) for the final image. Compare this to a multi-pass forward renderer, which considers the scene multiple times depending on the number of lights, looking at each light that affects each object on-screen. It can be seen how the process does not scale well as the number of lights increases in the scene - inefficiencies are prominent when overdraw comes into play as objects that are occluded are still rendered despite being invisible.

That is not to say this deferred approach is without its own issues, namely memory consumption and the inability to handle transparent objects. There are a number of implications with the former as these buffers are indeed responsible for the material variety in the scene as well as the range of colours - more variety means more data properties, which means more buffers, more memory consumption and memory bandwidth required. Killzone 2 uses a 36MB memory buffer when factoring in its quincunx anti-aliasing, up against a 14.5MB buffer for a traditional forward renderer.

However, Killzone 2 also includes a more traditional forward renderer too. Transparencies do not work within a deferred rendering engine. Simply put, these include smoke and fire... particle effects, or alpha textures such as chain-link fences. There is no way to incorporate these within the deferred solution, so there is a fallback to a forward pass render that puts them into the scene. In general, these effects can tax the memory bandwidth and fillrate of the GPU, and given the brevity with which they are displayed, it was not surprising to observe a reduced resolution buffer for the more dynamic effects (rocket trails, explosions, flamethrower), which most will not notice.

Killzone 2 Analysis, Campaign 4.

The analysis continues with this breakdown of the fourth campaign. The environments become more impressive, more complex and more... vertical, but the gameplay doesn't really evolve so much... yet.

Killzone 2 Analysis, Campaign 5.

Into the fifth campaign and, yes, it's all-out urban warfare along with memorable face-offs against Arc Towers and ATACs.

Killzone 2 Analysis, Campaign 6.

The last campaign we'll reveal today is the superb-looking train sequence. As game moves into its last quarter, the variety is far more pronounced and the gameplay more satisfying.

Coming up in part three: the final round of Killzone 2 coverage as we round-up our technical analysis of the single-player experience. Guerilla Games have definitely left the best until last. Plus, we'll be giving our opinions on the game itself. Yes, a "review" if you will. Warp straight to the page now.

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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.