Mathematical modelling of the alcoholic fermentation of glucose by Zymomonas mobilis mobilis

The kinetics of alcoholic fermentation of a strain of Zymomonas mobilis, isolated from sugarcane juice, has been studied with the objective of determining the constansts of a non-structured mathematical model that represents the fermentation process. Assays in batch and in continuous culture have been carried out with different initial concentrations of glucose. The final concentrations of glucose, ethanol and biomass were determined. The following kinetic parameters were obtained: μ_max, 0·5 h^?1; K_s, 4·64 g dm^?3; P_max, 106 g dm^?3; Y_x/s, 0·0265 g g^?1; m, 1·4 g g^?1 h^?1; α, 17·38 g g^?1; β, 0·69 g g^?1 h^?1.     

Flow-based local optimization for image-to-geometry projection

The projection of a photographic data set on a 3D model is a robust and widely applicable way to acquire appearance information of an object. The first step of this procedure is the alignment of the images on the 3D model. While any reconstruction pipeline aims at avoiding misregistration by improving camera calibrations and geometry, in practice a perfect alignment cannot always be reached. Depending on the way multiple camera images are fused on the object surface, remaining misregistrations show up either as ghosting or as discontinuities at transitions from one camera view to another. In this paper we propose a method, based on the computation of Optical Flow between overlapping images, to correct the local misalignment by determining the necessary displacement. The goal is to correct the symptoms of misregistration, instead of searching for a globally consistent mapping, which might not exist. The method scales up well with the size of the data set (both photographic and geometric) and is quite independent of the characteristics of the 3D model (topology cleanliness, parametrization, density). The method is robust and can handle real world cases that have different characteristics: low level geometric details and images that lack enough features for global optimization or manual methods. It can be applied to different mapping strategies, such as texture or per-vertex attribute encoding.     

Stereo Light Probe

In this paper we present a practical, simple and robust method to acquire the spatially‐varying illumination of a real‐world scene. The basic idea of the proposed method is to acquire the radiance distribution of the scene using high‐dynamic range images of two reflective balls. The use of two light probes instead of a single one allows to estimate, not only the direction and intensity of the light sources, but also the actual position in space of the light sources. To robustly achieve this goal we first rectify the two input spherical images, then, using a region‐based stereo matching algorithm, we establish correspondences and compute the position of each light. The radiance distribution so obtained can be used for augmented reality applications, photo‐realistic rendering and accurate reflectance properties estimation. The accuracy and the effectiveness of the method have been tested by measuring the computed light position and rendering synthetic version of a real object in the same scene. The comparison with standard method that uses a simple spherical lighting environment is also shown.     

Effective Annotations Over 3D Models

Annotation support in interactive systems is often considered a simple task by the CG community, since it entails the apparently easy selection of a region and its connection with some information. The reality appears more complex. The scope of this paper is two-fold: first, to review the status of this domain, discussing and characterizing several approaches proposed in literature to manage annotations over geometric models; second, to present in detail an innovative solution proposed and assessed in the framework of Cultural Heritage (CH) applications, called ClippingVolumes. At the annotation definition stage ClippingVolumes uses 3D data to characterize the annotation region; subsequently, annotations are visualized by adopting a two-pass rendering solution which uses stencil buffers, thus without introducing new geometric elements, changing the topology or duplicating geometry elements. It solves most of the issues that afflict the current state of the art, such as fragmentation, annotation transfer to multiple representations and multi-resolution data encoding. The latter is a mandatory requirement to produce efficient web-based systems. We implemented and we fully tested this approach in the framework of a complex system that supports the documentation of CH restoration projects.     

Virtual inspector: a flexible visualizer for dense 3D scanned models.

Virtual inspector lets novice users inspect dense 3D models at interactive frame rates on commodity PCs. The system obtains visualization efficiency without sacrificing quality by adopting a continuous level-of-detail representation. Visual inspector's use of XML to encode the GUI's structure and behavior makes it flexible and configurable. We can improve the virtual inspector system by adding new functionality and increasing its efficiency. Few restorers would consider the simple visualization of a digital 3D replica as the ultimate goal for the use of 3D scanning technologies in cultural heritage contexts. Once we can visualize an artifact with great accuracy, the need to map other data on the 3D model will rise. We're working on a slightly extended version of the tool to support mapping and selective visualization of different sources of surface data. We're also developing tools to compute measures. Finally, we're working to more dynamically enrich the data linked to the mesh by letting users add annotations or link multimedia material to selected points of the artifact surface. Our goal is to transform virtual inspector into a more dynamic instrument for cultural heritage research and restoration.     

Restoring David using 3D

Refurbishing Michelangelo's David has produced several useful restoration guidelines. These guidelines can help restorers select the proper procedures for the task and, objectively, assess the results. The work also has helped us develop innovative ways to process and visualize 3D data in cultural heritage projects. The David restoration was an ideal test bed. We try various methodologies to support restorers and scientists with visualization tools based on 3D digital models. 3D digital models can be a tool for undertaking specific investigations, or as supporting media for archiving and integrating the restoration-related information.     

A Statistical Method for SVBRDF Approximation from Video Sequences in General Lighting Conditions

We present a statistical method for the estimation of the Spatially Varying Bidirectional Reflectance Distribution Function (SVBRDF) of an object with complex geometry, starting from video sequences acquired with fixed but general lighting conditions. The aim of this work is to define a method that simplifies the acquisition phase of the object surface appearance and allows to reconstruct an approximated SVBRDF. The final output is suitable to be used with a 3D model of the object to obtain accurate and photo‐realistic renderings. The method is composed by three steps: the approximation of the environment map of the acquisition scene, using the same object as a probe; the estimation of the diffuse color of the object; the estimation of the specular components of the main materials of the object, by using a Phong model. All the steps are based on statistical analysis of the color samples projected by the video sequences on the surface of the object. Although the method presents some limitations, the trade‐off between the easiness of acquisition and the obtained results makes it useful for practical applications.     

Color to gray conversions in the context of stereo matching algorithms

This study tackles the image color to gray conversion problem. The aim was to understand the conversion qualities that can improve the accuracy of results when the grayscale conversion is applied as a pre-processing step in the context of vision algorithms, and in particular dense stereo matching. We evaluated many different state of the art color to grayscale conversion algorithms. We also propose an ad-hoc adaptation of the most theoretically promising algorithm, which we call Multi-Image Decolorize (MID). This algorithm comes from an in-depth analysis of the existing conversion solutions and consists of a multi-image extension of the algorithm by Grundland and Dodgson (The decolorize algorithm for contrast enhancing, color to grayscale conversion, Tech. Rep. UCAM-CL-TR-649, University of Cambridge, 2005) which is based on predominant component analysis. In addition, two variants of this algorithm have been proposed and analyzed: one with standard unsharp masking and another with a chromatic weighted unsharp masking technique (Nowak and Baraniuk in IEEE Trans Image Process 7(7):1068–1074, 1998) which enhances the local contrast as shown in the approach by Smith et al. (Comput Graph Forum 27(2), 2008). We tested the relative performances of this conversion with respect to many other solutions, using the StereoMatcher test suite (Scharstein and Szeliski in Int J Comput Vis 47(1–3):7–42, 2002) with a variety of different datasets and different dense stereo matching algorithms. The results show that the overall performance of the proposed MID conversion are good and the reported tests provided useful information and insights on how to design color to gray conversion to improve matching performance. We also show some interesting secondary results such as the role of standard unsharp masking vs. chromatic unsharp masking in improving correspondence matching.     

Visualization and 3D data processing in the David restoration

The program of scientific investigations planned in the framework of the restoration of Michelangelo's David produced several useful guidelines for defining and developing innovative ways to process and visualize 3D data in cultural heritage applications. Our ultimate goal was to include 3D graphics among the tools which can help restorers select the proper restoration procedures for the task at hand and objectively assess restoration results. For this, the David restoration was an ideal test bed to demonstrate the usefulness of digital 3D models and visualization tools in a restoration project. Because a complex set of scientific investigations was planned before and after the restoration intervention, we could try various methodologies to support restorers and scientists with visualization tools based on 3D digital models.     

Digital Fabrication Techniques for Cultural Heritage: A Survey

Digital fabrication devices exploit basic technologies in order to create tangible reproductions of 3D digital models. Although current 3D printing pipelines still suffer from several restrictions, accuracy in reproduction has reached an excellent level. The manufacturing industry has been the main domain of 3D printing applications over the last decade. Digital fabrication techniques have also been demonstrated to be effective in many other contexts, including the consumer domain. The Cultural Heritage is one of the new application contexts and is an ideal domain to test the flexibility and quality of this new technology. This survey overviews the various fabrication technologies, discussing their strengths, limitations and costs. Various successful uses of 3D printing in the Cultural Heritage are analysed, which should also be useful for other application contexts. We review works that have attempted to extend fabrication technologies in order to deal with the specific issues in the use of digital fabrication in the Cultural Heritage. Finally, we also propose areas for future research.