Shape from apparent contours for bent pipes with constant diameter under perspective projection.

• The single-view perspective projection model of a pipe with constant diameter is established. • Projected axis extraction method based on two facing apparent contours is developed. • A trinocular vision system is adopted to realize the 3D reconstruction of pipe axis. • After the pipe axis is reconstructed, the pipe radius can also be measured. In perspective projection images, apparent contours are important bases for recovering the three-dimensional (3D) shapes of constant diameter pipes (CDP). In order to complete the 3D reconstruction of CDP under perspective projection, this article first analyzes the single-view perspective projection model of CDP in detail. On this basis, coupled point pairs searching and projected axis extraction methods based on two facing apparent contours are proposed. After that, stereo vision technology is adopted to realize the 3D reconstruction of axis and the measurement of radius. Finally, the experiments with both synthetic and real data show that the proposed method has higher CDP reconstruction accuracy compared with the conventional method processed under orthogonal projection. [ABSTRACT FROM AUTHOR]