Building detection based on facet for urban reconstruction

This paper describes an approach to detect the building based on facet for urban reconstruction. The urban environment is composed of a variety objects. In particular, the building has a rich geometric structure. It consists of two or more facets. Each facet is presented with a quadrangle in the image. A quadrangle is produced by two or more vertical and horizontal lines. There are many lines which are orthogonal to each other on the building. The parallel lines in the 3D space are projected onto lines in the image plane that are grouped along the direction of vanishing points, provide strong cues for detecting the building facet in the urban environment. We detect the facet of building based on vanishing points. MSAC is used to estimate the dominant vanishing points in the image. These are separated into one vertical direction and two or more horizontal directions. An initial facet is made by a vertical and one of horizontal clusters. The building has a cubic structure with two orthogonal planes which meet at one line. The intersection points between two horizontal vanishing points are located on the intersection line of two facets. Finally, building facets are extracted by the geometric relationships between vertical and horizontal vanishing points.