Direct Illumination

Direct illumination plays the most noticeable part in rendering a synthetic scene, so it must be calculated as accurately as possible to avoid major artifacts. The procedure does not change when photon maps are applied, so everything works the way we implemented our homeworks: Cast a number of rays from the sampled surface point towards the light source to estimate the direct irradiance at that point. Then take this value and use it in a standard Phong shading formula to obtain the resultant color.