This paper describes sensors and algorithms developed and used for the creation of coloured 3-D triangular meshes from a set of range images with registered colour measurements. The objective is the creation of a digital model of a real object that is compatible with established computer graphics techniques. Triangular meshes are the fundamental rendering primitive supported by most high performance graphics workstations. The surface colour of objects can be represented by attributing reflectance values to the vertices of the mesh. Such a geometric and reflectance model provides a uniform and general representation for sculptured surfaces with non-uniform colouring.

We present an algorithm that reduces significantly the level of the registration errors between all pairs in a set of range views. This algorithm refines initial estimates of the transformation matrices obtained from either the calibrated acquisition setup or a crude manual alignment. It is an instance of a category of registration algorithms known as iterated closest-point (ICP) algorithms. The algorithm considers the network of views as a whole and minimizes the registration errors of all views simultaneously. This leads to a well-balanced network of views in which the registration errors are equally distributed, an objective not met by previously published ICP algorithms which all process the views sequentially. Experimental results show that this refinement technique improves the calibrated registrations and the quality of the integrated model for complex multi-part objects. In the case of scenes comprising man-made objects of very simple shapes, the basic algorithm faces problems common to all ICP algorithms and so must be extended.

This paper presents a new and general solution to the problem of range view integration. The integration problem consists in computing a connected surface model from a set of registered range images acquired from different viewpoints. The proposed method does not impose constraints on the topology of the observed surfaces, the position of the viewpoints, or the number of views that can be merged. The integrated surface model is piecewise estimated by a set of triangulations modeling each canonical subset of the Venn diagram of the set of range views. The connection of these local models by constrained Delaunay triangulations yields g non-redundant surface triangulation describing all surface elements sampled by the set of range views. Experimental results show that the integration technique can be used to build connected surface models of free-form objects. No integrated models built from objects of such complexity have yet been reported in the literature, It is assumed that accurate range views are available and that frame transformations between all pairs of views can be reliably computed.>

Building integrated models of existing 3-D objects is a key requirement for both reverse engineering and object recognition systems. An automatic 3-D model builder goes through three main steps: i) surface sampling from many views, ii) registration of the sampled views, and iii) integration of the registered views. The accuracy obtained depends on the acquisition and registration errors. The latter is critical since a misalignment of the range views causes their noise distributions to be centered around different means, which makes it difficult to reduce the effect of the acquisition error by simple averaging. In this paper, we propose a general algorithm that reduces significantly the level of the registration errors between all pairs in a set of range views. This algorithm refines initial estimates of the transformation matrices obtained from the calibrated acquisition setup. It considers the network of views as a whole and minimizes the registration errors of all views simultaneously. This leads to a well-balanced network of views in which the registration errors are equally distributed. Experimental results show an improvement of both the calibrated registrations and integrated models.>

A multiresolution surface modeling technique is presented. Several registered range views obtained from different viewpoints are first integrated into a nonredundant surface triangulation. The integration technique is based on the reparameterization of the canonic subsets of the Venn diagram of the set of views. The resulting triangulation is then input to a sequential optimization process that computes different levels of resolution of the surfaces of interest.>

Presents a dynamic approach for the integration of multiple registered range views. A nonredundant surface model for N views is computed from the model built from N-1 views by reprocessing only the surface segments seen in the Nth view. The integration technique is based on the reparametrization of the canonic subsets of the Venn diagram of the range views. The resulting surface model consists in a triangulation defined in an object-centered reference frame.>

The authors present a surface triangulation technique for surface description at different levels of resolution in a range image. A step discontinuity constrained 2-1/2-D triangulation of all points is first computed. A sequential optimization process then removes, at each iteration. the point that minimizes the local retriangulation approximation error caused by its removal. The iterative process can stop at any time to obtain a desired level of approximation error.>

A surface approach for the integration of registered 3-D range images, is presented. The method is a two-step algorithm based on the theory of sets. The proposed algorithm can deal with any number of views and is tailored for parallel implementation. Experimental results obtained by applying this algorithm to complicated objects showed that it is both effective and reliable. An advantage of the method is that it allows view interlacing. A surface segment not viewed because of the presence of a step discontinuity can be viewed by a view taken from another viewpoint.>