debugging and suppressing poisson distribution for single-photon flashs.

(cherry picked from commit f3d82bcb2a18878b4a661f7fbd91db7e8d11af7d)
auto reformat propagation kernel using the clang-format tool.

no actual changes have been made in this commit.
hole ice: beginning to implement cylinder

(cherry picked from commit f20a465661b054dab97c5192d7c2af0c2bf461af)