Fix FastSweeping call in sdfToExt and fix comments on the op parameter.
Fix FastSweeping call in sdfToExt and fix comments on the op parameter.

Signed-off-by: Andre Pradhana <825a1bc3df256148afa0e85b15649bcb998dccc3@dreamworks.com>

dreamworksanimation/openvdb,dreamworksanimation/openvdb,dreamworksanimation/openvdb,dreamworksanimation/openvdb