Abstract: A ray is cast into a volume described by a volumetric data structure, which describes the volume at a plurality of levels of detail. A first entry in the volumetric data structure includes a first set of bits representing voxels at a lowest one of the plurality of levels of detail, and values of the first set of bits indicate whether a corresponding one of the voxels is at least partially occupied by respective geometry. A set of second entries in the volumetric data structure describe voxels at a second level of detail, which represent subvolumes of the voxels at the first lowest level of detail. The ray is determined to pass through a particular subset of the voxels at the first level of detail and at least a particular one of the particular subset of voxels is determined to be occupied by geometry.

Abstract: Airports and other public places require security measures for the screening of human subjects for illicit objects and materials concealed from view beneath clothing. However, at present most of such screening processes involve only metal detectors, which are inherently incapable of detecting non-metallic illicit objects and materials. For this reason, there remains a strong need for novel systems and methods that can detect all types of materials. The present invention provides for a portal detection system that is configured for safe, rapid, and non-invasive scanning of human subjects. For this purpose, the portal detection system utilizes acoustic technology to achieve this end. The portal detection systems of the present invention may optionally be used in conjunction with conventional metal detection means. The invention encompasses portal detection systems, their use in scanning human subjects, and corresponding methods of scanning human subjects for illicit objects and substances.