Portal Extraction Based on an Opening Labeling for Ray Tracing

Abstract

Rendering photo-realistic images from a 3D scene description remains a challenging problem when processing complex geometry exposing many occlusions. In that case, simulating light propagation requires hours to produce a correct image. An opening map can be used to extract information from the geometry of the empty space of a scene, where light travels. It describes local thickness and allows to identify narrow regions that are difficult to traverse with ray tracing. We propose a new method to extract portals in order to improve rendering algorithms based on ray tracing. This method is based on the opening map, which is used to define a labeling of the empty space. Then portals - 2D surfaces embedded in empty space - are extracted from labeled regions. We demonstrate that those portals can be sampled in order to explore the scene efficiently with ray tracing.