For performance reasons, however, HBAO is typically rendered at half-resolution, as in Battlefield: Bad Company 2 and Battlefield 3, reducing the number of AO pixels by three-quarters . Unfortunately, rendering HBAO at reduced resolutions inevitably causes flickering that is challenging to hide in all situations – Battlefield 3’s HBAO selective temporal filtering helps, but in some cases flickering persists.
To overcome these issues, NVIDIA’s Louis Bavoil has completely redeveloped and revamped Screen Space Ambient Occlusion to create HBAO+, a paradigm shift in the field SSAO rendering. In comparison to HBAO, HBAO+ doubles the detail level of the AO effect, runs three times faster, aand uses the latest DirectX 11 technologies.
HBAO+ provides cutting-edge shadow tech for Splinter Cell Blacklist.
The world of Tom Clancy’s Splinter Cell Blacklist is full of shadows, demanding new, cutting-edge shadow tech that only HBAO+ can provide.
The first goal for Louis at the outset of his work was to create an AO technique that could be rendered fast enough at full resolution at 1920x1200, on a modern GPU like the GeForce GTX 660. HBAO offered good definition at full resolution, but its crippling performance impact made it impractical for modern games, and when it was used at a reduced resolution it still had a heavy impact on frame rates in comparison to SSAO, as observed in Far Cry 3.
Louis’s second goal was to maximize the efficiency of the AO implementation by leveraging the software advances brought to the table by DirectX 11 when launched it in 2009 (in particular texture arrays and gather4 instructions). Ultimately, the new DirectX 11 hardware and software enabled Louis to render HBAO+ with a fast Interleaved Rendering technique instead of a slow Fullscreen Pass.
Louis’s third and final goal was to improve the visual fidelity of HBAO+ in comparison to HBAO, especially in scenes with grass, leaves, and other fine detail. As seen in Far Cry 3, HBAO struggled in such situations, creating overbearing, solid areas of shadowing.
