Aliens vs. Predator (PC) supposed to kick consoles‘ ass - at least technology wise
With Aliens vs. Predator a new game of the popular AvP franchise is scheduled for February. PC Games Hardware interviewed Kevin Floyer Lea, Head of Programming at Rebellion, and received very interesting technical information.
Currently Aliens vs. Predator is scheduled for release in February 2010 and will become available for PC, PS3 and Xbox 360 in most parts of the world - but not in Germany. The PC version of the action game will also offer several features that cannot be realized on the consoles, like for example DirectX 11. Thus AvP will be one of the first titles to make use of features delivered by DirectX 11. We already know about the Hardware Tessellation that is used for more detailed characters, but from our email interview with Rebellion's Head of Programming Kevin Floyer Lea we learned that the engine also offers HDR lighting, Tone Mapping, Screen Space Ambient Occlusion and several other effects. Besides all those graphical features that make the PC version of Aliens vs. Predator look even better than the game looks on the consoles, PC gamers will also benefit from multi-core systems.
PCGH: Did you develop your own engine for Aliens versus Predator or did you license a technology? What were the reasons to do so? What are the advantages when utilizing your own technology or using a commercial product?
Kevin Floyer Lea: We use our own engine for all the games we make at Rebellion. It means that we have full control over every feature available in the engine and can tailor it to the needs of every game we make.
PCGH: You announced that your game is developed for PC, Xbox 360 and PS3. Will the engine be a pure cross-platform product or will there be an optimized version for the PC? If there is a special built for the PC what technical feature can't be realized with the console version or in other words are there any features the PC is the ideal platform to develop for?
Kevin Floyer Lea: The PC version of AvP is fully able to take advantage of the features of all the latest video cards and is optimized to make efficient use of multicore threading if your PC supports it. We will also be one of the first games to really show off how good DirectX 11 games can look, with hardware tessellation of the Aliens using displacement mapping, and Shader Model 5.0 Compute Shaders for post-processing effects.
PCGH: Are there any differences between the Console and the PC Version as far as technical as well as visual aspects are concerned?
Kevin Floyer Lea: All the art assets are authored at higher resolutions than can be squeezed onto current console hardware so, while AvP looks fantastic on Xbox 360 and PS3, it looks truly state-of-the-art on PC. Similarly effects such as shadows and full-screen passes like ambient occlusion are more complex and detailed on PC.
PCGH: Having a closer look at the few released PC Screenshots it becomes clear that a very detailed visual presentation seems to play an important role while developing Aliens versus Predator. Do you leverage very modern rendering techniques like Parallax Occlusion Mapping, Soft Shadows, HDR, a lighting model with Deferred Shading, Screen Space Ambient Occlusion, Shader Model 4.0 or post effects like Tone Mapping, Depth of Field or Motion Blur? If yes can you please give examples how this rendering techniques are utilized in Aliens versus Predator?
Kevin Floyer Lea: Yes! Dynamic lighting and shadows are absolutely key to the atmosphere of AvP: as a Marine you are constantly trying to survive in a dark environment - jumping at shadows and lighting your way forward with a flashlight and flares. Each of the three species sees the environment differently and creatures like the Alien are able to see clearly in areas that would otherwise appear pitch black to both the Marine and the Predator. We would not be able to achieve these kinds of effects without an HDR lighting model and Tone Mapping. Deferred Rendering allows us to use all these effects together in a way that would not otherwise be possible. I remember when we implemented and turned on the Screen Space Ambient Occlusion for the first time and everyone just went "wow!”...it brings a whole new level of lighting realism and solidity to everything. It's hard to imagine how we ever did without it!
PCGH: When Developing do you try to leverage very modern PC-Technologies like Dual-GPU-Rendering/SLI- or Crossfire-Systems? In other words: As far as overall performance is concerned, can players increase it remarkably by buying a second graphics card or a card with two GPUs? Do you have to add the support for multi GPU setting when developing the PC Version?
Kevin Floyer Lea: While in theory you could get a 100% improvement in performance with two matched GPUs, in practice it's never quite that simple. We're aiming for a minimum of a 50% improvement in performance - though it may be higher especially when GPU-bound. When developing the PC version we always have to keep multi GPUs in mind, as any effects that rely on the data from the previous frame (for example, a persistent motion blur, or using the previous frame's brightness for dynamic exposure control) will cause stalls as the data is passed between GPUs. We have to be careful to avoid any such problems.
PCGH: It is no secret that the Xbox 360 and even the PS3 is a suitable platform for a multi threaded engine. As a consequence of this, is the technical base of the PC version heavily optimized for multithreading?
Kevin Floyer Lea: Absolutely, our experience with multithreading on all platforms works to the advantage of the performance of the game - and the PC version is no slouch in this department.
PCGH: How many cores are supported? What different tasks can be or are split up into different threads and what is the expected performance gain resulting from two respectively four or even more (8) cores?
Kevin Floyer Lea: Some tasks such as streaming textures, or sounds, are given an extra thread each which runs in the background whenever there is work to do. Other more complex systems generate as many threads as the PC has cores. For example the physics system will use 8 threads if the game is run on an 8 core machine, spreading the load as equally as possible.
PCGH: Does your game offer an advanced physics-simulation? If so, do physics have an impact on gameplay or do you use physics only to offer more eye candy?
Kevin Floyer Lea: We use our own physics-simulation solution in the game and it's at the root of everything. It controls how the characters collide with the environment - allowing us to do crazy things like have Aliens crawling on walls and ceilings. We have the obvious stuff like objects that you can knock around and destroy, but we also use physics in more subtle ways too. Our inverse-kinematics are used to make sure that the feet of characters connect accurately with the floors, slopes or steps that they are moving on. We also use IK to procedurally generate the animation of the long Alien tails and make sure that they collide correctly with the environment and don't poke through it as they trail fluidly behind the characters.
PCGH: Do you program your own physics engine or do you utilize middleware? Will the PC version of Aliens versus Predator furthermore support hardware accelerated physics (Nvidia Physx)? What is your personal opinion about the topic GPU physics?
Kevin Floyer Lea: We wrote our own physics engine designed for the needs of Aliens vs Predator. We don't currently support GPU physics, though the way the engine is structured it's entirely possible to take advantage of such hardware in the future, especially with Shader Model 5.0 which will work across all DirectX 11 GPUs. However, we usually find that if the GPU has more power, we want to use it for better looking visuals! We are expecting to use new techniques in the future which will require any increase in GPU power.
Kevin Floyer Lea: Yes - AvP fully supports Windows XP, Vista and Windows 7.
PCGH: When do you think game development will be at a juncture where it's more viable to put all the effort into one rendering-path using only DirectX 11 (with downlevel-paths) and drop support for XP?
Kevin Floyer Lea: It's a difficult question, as XP is still very popular with many people. As a company we've used DirectX since it first came into existence at the time of Windows 95, so we are experienced with upgrading and supporting different versions of Windows and DirectX... but XP only supporting DirectX 9 is definitely slowing progress. We're currently hoping Windows 7 does well - hopefully in another year or two most gamers will be on Vista or Windows 7 and we can concentrate on DirectX 11 ... or 12!
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