Computer Interpretation Of Line Drawings For Representing Planar Objects Under Axonometric Projection

A line drawing is an important medium that human exchanges information of three-dimensional scenes with computer. Computer interpretation of line drawings is very important in computer vision, reverse engineering, and intelligent CAD system. When we see a line drawing that is the projection of a three-dimensional scene, we can easily understand what is represented there, for computers, on the other hand, and it is difficult. Computer interpretation of line drawings is basis of reconstructing three-dimensional scenes from images.In this thesis, the main work consists of two parts: the first part is to make use of the constraints between points and planes of three-dimensional planar object in computer interpretation of line drawings; We studied the constraints between points and lines and those between lines and lines of three-dimensional planar object in computer interpretation of line drawings in the second part. Adopting these two kinds of methods, the hidden-parts-drawn and the natural line drawings are interpreted, and experiments show that our methods for inferring line drawings are successful.It is introduced the representations of straight lines in two-dimensional plane and three-dimensional space, line drawing labeling, the theory and methods of computer interpretation of line drawings based on the relative position relationships of the vertices and the planes on a planar object. Based on the existed method for interpreting line drawings, we put forward a kind of recursive method for computer interpretation of line drawings under orthographically axonometric projection. Our method can be used to interpret to the hidden-parts-drawn and the natural line drawings. The natural line drawing is the one with hidden-parts-eliminated. Based on the correlative constraints between vertices and straight lines on a planar object, we have proposed a new recursive method for computer interpretation of linedrawings under orthographically axonometric projection. Our method can be used to interpret to the hidden-parts-drawn and the natural line drawings.By using of Visual C++6.0, we have developed a procedure for extracting two-dimensional coordinates of vertices and parameters of straight lines from a line drawing.The innovation in this thesis is that a new recursive method of computer interpretation of line drawings is put forward to based on a new way of thinking of the correlative positions between vertices and lines and the constraints between vertices and lines on a planar object. Some experiments are implemented. Compared with the recursive method based on the relationships between vertices and planes, our method for computer interpretation of line drawings based on the relationships of vertices and straight lines has the advantage that it is easier to obtained the three-dimensional structure of a line drawing from its two-dimensional structure.