Deformable model to recover circular generalized cylinders

This paper describes a new approach to recover Circular Generalized Cylinders (CGC) using deformable models . This class includes many objects present on industrial site (pipes) or on the natural environment (human leg, tree trunk) . First, we propose a modeling algorithm of objects with constant cross-section radius, called Uniform Circular Generalized Cylinder s (UCGC). With this assumption, reconstruction is possible from a single view of the object. In the case of a single image, the cross - section radius cannot be estimated . If this radius is unknown, reconstruction is achieved up to a scale factor. The model 3D axis i s parametrized by a B-spline curve . After a coarse initialization, the model changes shape to fit the object contour detected in the studied image. Using different views of the object, the previous approach is adapted to Circular Generalized Cylinders (cross-section radiu s variations are now permitted) . No assumption is made on the axis geometry nor on the way the radius varies . In order to be sufficiently adaptative to the large range of object shape belonging to this class, we propose using two independent B-splin e functions to model respectively axis and cross-section radii variations . These algorithms use the geometrical properties of the occluding contours given by the perspective projection of the objects. It i s the first attempt to solve this problem by taking into account this accurate projective model .Dans cet article, nous proposons une méthode de reconstruction des cylindres généralisés à section circulaire par modèle déformable. Tout d'abord, nous formulons l'hypothèse que les sections de l'objet sont de rayon constant. Nous parlons alors de Cylindres Généralisés Circulaires Uniformes (CGCU). Si le rayon est connu a priori, cette hypothèse permet de retrouver l'axe 3D de l'objet, paramétré par une fonction B-Spline, à partir d'une seule vue, sinon la reconstruction est faite à un facteur d'échelle près. Après une initilisation grossière, le modèle est déformé itérativement jusqu'à ce que sa forme devienne cohérente avec les contours extraits de l'image. Nous montrerons ensuite que l'exploitation de différentes vues d'un même objet permet d'adapter notre approche à la reconstruction de Cylindres Généralisés Circulaires (CGC), objets constitués de sections circulaires à rayon non-constant. Aucune hypothèse a priori n'est faite sur la géométrie de l'axe ou sur la façon dont varie le rayon des sections. Afin de pouvoir s'adapter au plus grand nombre d'objets appartenant à cette classe, deux fonctions B-Spline indépendantes sont utilisées pour paramétrer l'axe et la fonction de variation du rayon

Sensor system and related models to determine irregular shaped 3-D objects

This work comprises several parts, the initial part o f which is a review o f the techniques in use at present for measuring shape and characterising products. The major work details a ring sensor system, which consists o f a large number o f transmitters and receivers alternately arranged on the circumference o f a metal annulus. Using a modified polar co-ordinate system and trigonometric functions, two enveloping spirals o f an object can be determined. One or both spirals can then be used for further data analysis. Each spiral consists o f intersections between enveloping chords and parts o f the chords. The area surrounding the object is segmented and properties such as volume and axis measurements can be determined. A mode! was developed to simulate artificial objects o f various shapes. Simulation tests were carried out to determine the limits o f the system concerning position within the ring, shape and speed o f the object and resolution o f the ring. A ring was manufactured for actual tests, which were carried out mainly on potatoes to confirm the possible use in practice and to show the relative merits compared with existing systems. Interesting side issues are introduced, such as the low number of primary data, possibilities of further reduction using differential coding, and the consumption time of the algorithms. Finally, a model for the simulation o f more than one object in the ring at the same time is introduced and a possible way o f separation is investigated