It is very significant to simulate non-line-of-sight (NLOS) light propagation in complex terrain. The single-scatter theory is always used to study the NLOS light propagation inland and abroad now

but only single-scattering photons are calculated approximately by the method. Furthermore

if the weather is bad or the transmission distance is large comparatively

much larger error will occur. So the single-scatter model is unfeasible when photons enter the detector inevitably by multiple scattering (two or more). In the paper

considering emission and detector don’t have the visual angle in common

the multiple-scattering theory based on Monte Carlo (MC) method is described here to calculate two typical instances: the detector and emission are in opposite directions and the visual angle of the detector is limited by the obstacles in front. Accordingly

a solution is presented in detail to simulate the light propagation when the detector and emission do not have mutual scattering-substance. And the correct results are obtained according to the comparative experimental results

which is very practicable in complicated conditions.