Originally Posted by Anandtech
But what if there was a way to have a forward renderer with performance similar to that of a deferred renderer? That’s what AMD is proposing with one of their key tech demos for the 7000 series: Leo. Leo showcases AMD’s solution to the forward rendering lighting performance problem, which is to use a compute shader to implement light culling such that the compute shader identifies the tiles that any specific light will hit ahead of time, and then using that information only the relevant lights are computed on any given tile. The overhead for lighting is still greater than pure deferred rendering (there’s still some unnecessary lighting going on), but as proposed by AMD, it should make complex lighting cheap enough that it can be done in a forward renderer.
As AMD puts it, the advantages are twofold. The first advantage of course is that MSAA (and SSAA) compatibility is maintained, as this is still a forward render; the use of the compute shader doesn’t have any impact on the AA process. The second advantage relates to lighting itself: as we mentioned previously, deferred rendering doesn’t work well with complex materials. On the other hand forward rendering handles complex materials well, it just wasn’t fast enough until now.
Leo in turn executes on both of these concepts. Anti-aliasing is of course well represented through the use of 4x MSAA, but so are complex materials. AMD’s theme for Leo is stop motion animation, so a number of different material types are directly lit, including fabric, plastic, cardboard, and skin. The total of these parts may not be the most jaw-dropping thing you’ve ever seen, but the fact that it’s being done in a forward renderer is amazingly impressive. And if this means we can have good lighting and excellent support for real anti-aliasing, we’re all for it.
