Method of simulating lighting at a point of a synthesized image

A method of simulating lighting at an estimation point of an image synthesized in three dimensions describing a scene provided with at least one light source, said estimation point being situated on a surface, said method comprising the following steps:

• selecting a cloud of virtual photons (photon map) by sending photons from said at least one light source and by following the paths of said photons, each interaction with a surface of the scene potentially generating a new photon in the cloud, and storing at least one surface characteristic of the surfaces touched by said photon;
• and
• selecting a local volume of said photon map arranged around said estimation point;
• the method comprising the following steps:
• analyzing the photons contained in said local volume to detect the presence of at least one other surface different from said surface and extending in the vicinity of said estimation point, said local volume contains “valid” photons having surface position and orientation characteristics similar to those of the estimation point, and “invalid” photons having surface position and orientation characteristics different from those of the estimation point, said method comprising making use of the invalid photons contained in said local volume to detect said at least one other surface in the vicinity of said estimation point;
• and
• calculating the indirect lighting at said estimation point while taking account of said at least one other detected surface.