Friday, 15 October 2010

Tech Report: DLAA Used In SW:Force Unleashed II

Nowadays it seems like everyone is experimenting with various forms of anti-aliasing. Titles such as MGS4, DMC4, and Halo Reach use a form of temporal AA - edge smoothing which works by blending two frames together to eliminate jaggies, whilst others like God Of War 3 and Little Big Planet 2 use morpthalogical AA, a method that works on depth buffers and individual pixels in each frame resulting in up to 16xMSAA on some surfaces, and 4x on most. Now LucasArts are joining the club with their latest Star Wars action game.

In Star Wars: The Force Unleashed 2, the developers are using something called Directionally Localized Anti-Aliasing (DLAA), which looks to be similar to MLAA in its effects and implementation, though it appears to work on a directional, positional type basis (possibly multiple frame) leading to some undesirable artefacts in motion.

The tech is undeniably impressive, and the 360 demo showcases what looks like being the most accomplished form of AA on the platform so far, regardless of a few noticeable shortcomings.

The screenshots below (thanks IGN) show the DLAA working under somewhat ideal conditions, with very little in the way of inconsistant, fast-paced movement present in the scene. Notice how clean looking the entire image is. There’s very little, to no aliasing at all, and even smaller pixels get smoothened over successfully.

Unfortunitely, due to the way this form of AA seems to work, in scenes with quick camera pans, and fast moving objects there is noticeable artifacting. This also seems to be the case when directionality and positioning of the light sources in the scene change in accordance with the action. When this happens not all surfaces get AA, with some missing out on edge smoothing almost entirely.

The artifacting caused by the AA in these screens is also joined by other undesired side effects from the game’s use of motion blur, which tends to accentuate the overall amount of artifacting in the scene. However, it is also hard to tell whether it is just the AA causing problems, the motion blur, or a combination of both.

You can see this below:

Either way the use of DLAA in SWFU2 is very impressive, though not faultless, and has a very similar effect to MLAA with regards to edge smoothing. It’s not quite as polished, or a beautifully clean as MLAA however, although it does provide a workable alternative to traditional 2x and 4xMSAA at a lesser cost.

A high quality implementation of SSAO is also visible in the screenshots, and in the actual demo. There’s minimal artifacting, and a nice amount of additional depth.

And another thing. Despite being released by the press, these screens certainly are not bullshots - the demo available on the Xbox Live looks exactly the same. SWFU2 renders in 1280x720p on the 360 at least, with DLAA providing the high quality edge smoothing on offer here.

This is the first time that any developer has attempted this type of AA on the Xbox 360, and the results are very impressive, and the outlook positively optimistic. The use of alternative, less memory intensive forms of edge smoothing could easily have a beneficial effect on use of the 360’s EDRAM for other rendering tasks, freeing it up for developers to use on improving other graphical areas in the pipeline, pushing the boundaries of the hardware further than initially thought possible. But until then, this is a firm shift in the right direction.

DLAA is also being used in the PS3 build of the game (implemented on the SPU’s) and on the PC (on the GPU), although we haven’t had a chance to try either version out. But I imagine that overall image quality should be the same, assuming identical rendering resolutions and alpha buffers for effects.

Thanks go out to AlStrong for counting those pixels, and IGN for the screens.

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