1 Introduction

The automated reconstruction of realistic 3D models of a scene is relevant in many disciplines. The approach usually adopted is based on an ``inverse optic'' procedure, a simple model of which is, for instance, binocular vision. Accordingly, the third dimension (field depth) is reconstructed by merging the information extracted from 2D monocular images.

We designed and realized a network service named WEB3R, Web-based 3D Reconstruction, based on the HTTP protocol to manage the remote reconstruction of 3D scenes.

The main idea behind WEB3R is reconstructing on demand, according to the well-known client-server paradigm: the user/client connects to the service and, interacting with the system in several ways - by setting parameters, or correcting unexpected results, ... - obtains a graphical model from a sequence of input images.

Examples of interactive systems managed via web are present on the Internet. The Institute for Theoretical Neurophysics, University of Bremen (D) hosted a Web-based Image Processing system [1]. At present there is an off-line version of the service: some web pages act as interface, but it's not possible to interact with the system any more. The service provided the following resources: stereo vision; segmentation; edge extraction; texture and gradients; color-separations and histogram-manipulations.

The stereo vision section contains the documentation about the algorithms used: both a new method [4] and the standard one based on correlation. The INRIA Institute [2] presents an interactive demonstration of the computation of the epipolar geometry: the user provides a stereo pair and the system searches for the matches and the related fundamental matrix. The user can change parameters - i.e., the threshold and maximum number of iterations in relaxation - to obtain better results.

Another interesting service is supplied by the Geoscience Australia [3]: an on line system - part of the Geoscience Awareness education kit "Discovering Remote Sensing" - processes the satellite data for the Murwillumbah area on the east coast of Australia. The system allows the following operations on the images: Zoom in and pan; Brightness setting; Representation (RGB, vegetation index, water depth, water chlorophyll).

WEB3R is intended to provide greater flexibility, being useful not only to obtain finalized models, but also to support research/development and instruction.

Especially in connection with the former aspect, the system is proposed as a testbed for research in the field of stereo vision. From the educational point of view, WEB3R can be considered a remote laboratory to experiment in the field of (multi) stereo reconstruction.