Acquisition And Representation Of Object Surface Data

Abstract

A simple, low cost, and universal automatic 3 -D acquisition system was developped using active triangulation. Its main characteristics are:-its speed of acquisition (about 1 minute per object), -the density of its sampling (from 30,000 to 250,000 measures per object), -the structured lattice of the resulting data (distributed on parallel and meridian equidistant lines). From these data, it is possible to use several techniques of surface approximation to

Some aspects of parametric surface meshing

“…Any point with coordinates (x = sin 1 , y = sin 2 ) is therefore located inside the square [− sin 1 and remains constant afterwards. Therefore, if the mesh is sufficiently regular so that angle between two edges is always between 40 • and 140 • , then the angular deviation of an element remains below 31 • , which is a generally acceptable threshold.…”

“…− → v ) on the tangent plane. We consider angles 1 where is fixed, and x and y are real variables. The equation z=f (x, y) defines a Cartesian surface whose minimum is at the point (0, 0, 0).…”

“…Indeed, this representation is widely used, especially in CAD (computer aided design) environments using the B-Rep (boundary representation) model. It can also be used after an interpolation of a structured grid of points, resulting for instance from a 3D digitizer [1]. Another typical case is that of a surface composed of simple geometric shapes, like portions of planes, spheres or tori, modeling for example industrial parts or even molecular surfaces in computational chemistry [2].…”

Animation of a B-Spline figure

“…What varies according to culture are "the rules for emotional expression or the conditions for the release of each emotion" [7], but not the use of specific muscles related to each expression. In order to simulate the principal emotions, we have experimented with the displacements of the characteristic points, especially the movement of eyebrows, the dilation of the eyes, the form of the mouth and the creases of the checks.…”

“…The face's data that we used have been obtained by an automatic 3-D digitizing system elaborated by the laboratoire Image of the Ecole Nationale Superieure des Telecommunications [7]. It has about 70000 points organized in slices going from the top to the bottom of the head.…”