Bounding box and projections detection of hidden polygons in

Abstract

An image is generated from a database of three-dimensional object data where each the objects is formed from at least one polygon having at least one edge. Successively determinations are made as to whether a particular one of the object polygons designated as the test polygon is not visible to an observer located at a predetermined location by virtue of being hidden by other objects in the database. If the test polygon is determined to be not visible, then it does not need to be rendered by an image renderer and may be discarded. The decision is made by successively selecting one of the three-dimensional object in the database. After an object is selected, each of the object polygon is selected to determining whether the polygon is occulted by another object. This determination is performed by determining the exterior region of the object as the union of bounding boxes of exterior polygons, determining the interior region of the object as the union of bounding boxes of interior polygons, and testing for overlap between the projected bounding box of the polygon and the projected bounding boxes of the exterior polygons and the projected bounding boxes of the interior polygons. The test polygon is determined to possible be visible or to be not visible based on overlaps between the projected bounding boxes of the test polygon, the interior polygons, the exterior polygons, and coordinate values. Polygons that are not visible are discarded while polygons that may be visible are retained.