Ambient occlusion is ubiquitous in games and other real-time applications
to approximate global illumination effects. However there
is no analytic solution to ambient occlusion integral for arbitrary
scenes, and using general numerical integration algorithms is too
slow, so approximations used in practice often are empirically made
to look pleasing even if they don’t accurately solve the AO integral.
In this work we introduce a new formulation of ambient occlusion,
GTAO, which is able to match a ground truth reference in half a
millisecond on current console hardware. This is done by using
an alternative formulation of the ambient occlusion equation, and
an efficient implementation which distributes computation using
spatio-temporal filtering. We then extend GTAO with a novel technique
that takes into account near-field global illumination, which
is lost when using ambient occlusion alone. Finally, we introduce a
technique for specular occlusion, GTSO, symmetric to ambient occlusion
which allows to compute realistic specular reflections from
probe-based illumination. Our techniques are efficient, give results
close to the ray-traced ground truth, and have been integrated in
recent AAA console titles.
Click here to read the full technical report: PDF
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