depthMipChain property
Renders the depth prepass at full resolution and samples it through a downsampled mip chain (a level per sample distance), instead of rasterising the depth at the occlusion resolution.
This is the Scalable Ambient Obscurance depth-mip design. It keeps the depth accurate where the projection compresses a large range into few pixels (a steep grazing surface or a vertex-displaced "curved world"), so the occlusion of near geometry is not contaminated by the far surface behind it, and it keeps large radii cache-friendly. The cost is a full-resolution depth prepass plus the chain build, so it is off by default and best reserved for higher-end targets.
Implementation
bool depthMipChain = false;