SSDO: Screen Space Directional Occlusion
SSDO or Screen Space Directional Occlusion is a new method for approximating real time global illumination (GI). It can be seen as an improved version of the SSAO (screen space ambient occlusion) method with one bounce of indirect illumination.
With SSDO, red and blue shadows are visible, whereas AO shadows are completely grey.
The paper that describes the SSDO method is available HERE.