Nicola Brusco

Automatic 3D modeling of textured cultural heritage objects

A widespread use of three-dimensional (3D) models in cultural heritage application requires low cost equipment and technically simple modeling procedures. In this context, methods for automatic 3D modeling of textured objects can play a central role. Such methods need fully automatic techniques for 3D view registration and for the removal of texture artifacts. The paper proposes an image processing based procedure that is very robust and simple. It does not require special equipment or skill in order to make textured 3D models. These proposals, originally conceived to address the cost issues of cultural heritage modeling, can be profitably exploited also in other modeling applications.

A System for 3D Modeling Frescoed Historical Buildings with Multispectral Texture Information

This work proposes a system for the automatic construction of multi-spectral three-dimensional (3D) models of architecture. Besides the specific application, which concerns the interactive visualization and the restoration of historical buildings, the interest of the proposed system lies in the instrumental gap it fills in the multi-spectral nature of the textures, in general needed for rendering with faithful colors, and in the automatism of the 3D model construction. The paper presents a robust procedure for matching 3D points of architecture scenes and a new multiresolution method for texture generation. The proposed system is an effective tool for producing 3D content amenable to a great number of usages.

A novel framework for the interactive transmission of 3D scenes

We consider an interactive browsing environment for 3D scenes, which allows for the dynamic optimization of selected client views by distributing available transmission resources between geometry and texture components. Texture information is available at a server in the form of scalably compressed images, corresponding to a multitude of original image views. Surface geometry is also available at the server in the form of scalably compressed depth maps, again corresponding to a multitude of original views. Texture and depth components are both open to augmentation as more content becomes available. At any point in the interactive browsing experience, the server must decide how to allocate transmission resources between the delivery of new elements from the various original view bit-streams and new elements from the original geometry bit-streams. The proposed framework implicitly supports dynamic view sub-sampling, based on rate-distortion criteria, since the best server policy is not always to send the nearest original view image to the one which the client is rendering. In this paper, we particularly elaborate upon a novel strategy for distortion-sensitive synthesis of both geometry and rendered imagery at the client, based upon whatever data is provided by the server. We also outline how the JPIP standard for interactive communication of JPEG2000 images, can be leveraged for the 3D scene browsing application.

Greedy non-linear approximation of the plenoptic function for interactive transmission of 3D scenes

We consider an interactive browsing environment, with greedy optimization of a current view, conditioned on the availability of previously transmitted information for other (possibly nearby) views, and subject to a transmission budget constraint. Texture information is available at a server in the form of scalably compressed images, corresponding to a multitude of original image views. Surface geometry is also represented at the server in a scalable fashion. At any point in the interactive browsing experience, the server must decide how to allocate transmission resources between the delivery of new elements from the various original view bit-streams and new elements from the geometry bit-stream. The proposed framework may be interpreted as a greedy strategy for non-linear approximation of the plenoptic function, since it considers both view sampling and rate-distortion criteria. We particularly elaborate upon a novel geometry- and distortion-sensitive strategy for blending the information available from different views at the client.

Metrological analysis of a procedure for the automatic 3D modeling of dental plaster casts

As well known, in the reconstruction of the 3D models through optical systems, the errors are due to the single-view acquisition error and to the 3D modeling procedure. The latter can be ascribed to the various phases of the 3D modeling pipeline: pairwise registration, global registration, surface integration. This work examines the acquisition error as well as the errors due to an automatic procedure recently proposed for the 3D modeling of dental plaster casts. This contribution derives a simple error propagation model, rather useful for practical simulation purposes. From a general viewpoint, this contribution proposes a useful simulation of error propagation in 3D modeling, it shows the quality of an automatic 3D modeling procedure recently proposed and it shows the accuracy of 3D modeling dental plaster casts by current commercial range cameras and the considered automatic method.

Simultaneous acquisition of 3D shape and color texture from large frescoed areas

We present the recent results obtained by a system which measures both 3D shape and multispectral texture of artistic and architectural cultural assets. The system consists on a rangefinder device which acquires the range and a visible scanning spectrograph for colour texture analysis. This technique is applied to the acquisition of the cycle of Stories of Maria, a frescoed lateral chapel painted by Girolamo Tessari in 1523-1526 located in the church of S. Francesco in Padua (Italy).

Server Policies For Interactive Transmission Of 3D Scenes

We consider an interactive client-server application for remote browsing of 3D scenes. The information about texture and geometry is available at server side in the form of scalably compressed images and depthmaps, corresponding to a multitude of original image views. Image and depth components are both open to augmentation as more content becomes available. During the interactive browsing experience, the server allocates the available bandwidth between the delivery of new elements from the various original view bit-streams and new elements from the original geometry bit-streams. We propose a rate-distortion criterion to decide the best transmission policy for the server, since the best solution is not always to send the nearest original view image to the one which the client is rendering. We also outline how the JPIP standard for interactive transmission of JPEG2000 images can be exploited for remote exploration of 3D scenes

Passive reconstruction of high quality textured 3D models of works of art

A wide-spread use of 3D models in cultural heritage application requires low cost equipment and simple modeling procedures. In this context, passive 3D reconstruction methods allow to build 3D models from a set of calibrated cameras, without the need of expensive machinery. Unfortunately the surfaces characteristics often lead to bad quality reconstructions. Recent efforts attempt to combine together information from different passive methods in order to improve the overall quality of the result. The combination of stereo matching and silhouette information has recently received considerable attention. Typically the major contribution to the appearance of the model comes from texture, rather than from geometry. The straightforward application of the photographs over the model can lead to artifacts, due to errors in 3D reconstructions, which must be minimized. This work, building on recent results, proposes a variation of an algorithm for 3D geometry recovery from stereo and silhouette information within a classical deformable model framework, which improves the quality of the shape. In order to avoid visible texture artifacts, it also proposes a new algorithm for texture synthesis based on wavelet decomposition. Experimental verification shows the effectiveness of the proposed solution with respect to robustness, computational speed and quality of the final result.

Automatic 3D modelling of palatal plaster casts

We introduce a procedure for automatic 3D modelling and discusses its performance in the context of a medical application, namely the 3D modelling of palates casts. The general interest of the proposed method lays in the fact that a widespread use of 3D modelling in nonengineering applications requires automatic procedures. The specific interest is in the intriguing mixture of open issues concerning 3D modelling, geometrical metrology and medicine represented by the modelling of free-form surfaces of anatomical interest.

A Range Camera Collecting Multi-Spectral Texture for Architecture Applications

This work proposes a system for the automatic construction of multi-spectral 3D models of architecture. Besides the specific application which concerns the interactive visualization and the restoration of historical buildings, the interest of the proposed techniques lays in the multi-spectral nature of the textures which allow rendering with faithful colors and in the automatism of 3D model construction. The proposed system is an effective tool for producing 3D content amenable to a great number of applications.