PHOTOGRAMMETRY DRIVEN TOOLS TO SUPPORT THE RESTORATION OF OPEN-AIR BRONZE SURFACES OF SCULPTURES: AN INTEGRATED SOLUTION STARTING FROM THE EXPERIENCE OF THE NEPTUNE FOUNTAIN IN BOLOGNA

Checking the irreversible process of clean-up is a delicate task that requires a work of synthesis between theoretical knowledge and practical experience, to define an effective operating protocol on a limited patch area to be extended later to the entire artefact's surface. In this paper, we present a new, quick, semi-automated 3D photogrammetry-based solution to support restorers in the open-air bronze artwork cleaning from corrosion and weathering decay. The solution allows the conservators to assess in real time and with a high level of fidelity in colour and shape, the 'surfaces' to be cleaned before, during and after the clear-out treatment. The solution besides allows an effective and valuable support tool for restorers to identify the original layer of the bronze surface, developed and validated during the ongoing restoration of the Neptune Fountain in Bologna

The Rusterizer: An Art-Directable and Semi-Procedural Tool for Generating Rust Surfaces

The Rusterizer is an art-directable tool designed to facilitate the creation of rust on the surfaces of 3d models. Cellular automata are combined with a procedural shader to create an animated growth effect. A workflow for using the tool is provided. The result is demonstrated with a time-lapse animation of a robot in an alley as it rusts. Future extensions and improvements to the tool are suggested

Particle staining: physically based texture generation

Computers are being employed in a variety of ways by a variety of individuals to create imagery. Much work has been done to accurately model natural phenomena in the context of computer graphics as well as model specific artists' tools and techniques. Focusing on the dynamics of water flow across surfaces, it is the goal of this work to develop a physically inspired texturing tool that allows artists to create interesting staining and wearing effects on surfaces. Weathering or the wearing down of materials by natural forces can create complex and beautiful patterns on a variety of surfaces. In this process lies the very essence of the creative act. To distill the essence of the elements of the water staining process, we employ a computer generated particle system in a phenomenological model. The motion of these particles is controlled by physically based constraints, such as wind, gravity, mass, etc. The way in which each particle interacts with or modifies the look of the surface is further controlled by parameters such as surface roughness, surface color and surface hardness. Each particle can remove or deposit material as it flows across the surface, creating complex patterns

Applying the electroforming process to bio-inspired architecture: The case of Castelbuono Estate Winery

Abstract Inaugurated in June 2012, the Carapace at Castelbuono Estate Winery in Italy is a highly interesting example of biomorphic architecture. The structure, an artistic creation of world-renowned sculptor Arnaldo Pomodoro, is reminiscent of a tortoise shell that conveys a sense of protection: the Carapace structure guards wine barriques in the same way that the tortoise carapace protects the animal. Zoomorphic aspects are further exhibited by symbols on the roof, which remind observers of cuttlefish bone, a recurring element in the artistic production of Maestro Pomodoro. The roof was constructed by assembly of single copper plates with a rough surface in accordance with the design of the artist. Therefore, determining the appropriate production process was crucial. Electroforming was selected as the method to achieve a challenging architectural goal

Desarrollo de una celda electroquímica en gel para la evaluación in situ del patrimonio cultural metálico

A lo largo de toda la historia, la humanidad ha tratado de preservar ciertos objetos que por diversos motivos han adquirido un valor y un significado para la sociedad que los ha poseído, constituyendo su patrimonio cultural. En ese esfuerzo por preservar el pasado para las generaciones presentes y futuras, la investigación científica ha ido adquiriendo una relevancia progresiva. La ciencia de la conservación trata de comprender los problemas y aportar soluciones para la conservación del patrimonio, tanto desde el punto de vista tecnológico como estratégico o de sostenibilidad. El adecuado diseño y planificación de las estrategias de conservación de los objetos y colecciones del patrimonio cultural son fundamentales, y deben tener en cuenta las limitaciones tecnológicas y de recursos. El fin de esta tesis ha sido contribuir desde la Ciencia e Ingeniería de Materiales a este objetivo, concretamente en el ámbito del patrimonio cultural metálico, desarrollando una herramienta de diagnóstico del estado de conservación y de los sistemas de protección para este tipo de bienes culturales. El principal problema para la conservación del patrimonio metálico es la corrosión, que tiene lugar por interacción entre el objeto metálico y el medio que lo rodea. Para enfrentarse a este problema, los conservadores de patrimonio metálico cuentan con dos estrategias: el control de las condiciones ambientales –lo que no siempre es posible- o el empleo de recubrimientos protectores, que lo aíslen del medio, que es el método más habitual en la práctica de la conservación. Sin embargo, cualquier método presenta limitaciones, por lo que resulta de gran relevancia el poder evaluar la eficacia y la duración de los sistemas empleados, antes de que aparezcan efectos negativos en el objeto. Así, los recubrimientos habituales en conservación –principalmente ceras y barnices acrílicos- tienen una capacidad protectora bastante limitada y deben ser renovados cada cierto tiempo. Esto conlleva la necesidad de conocer y evaluar el comportamiento de los sistemas aplicados, con especial hincapié en su durabilidad. La espectroscopía de impedancia electroquímica (EIS) es una técnica electroquímica que permite estudiar los procesos de corrosión en los metales en diferentes medios y evaluar la capacidad protectora de los recubrimientos, por lo que a priori resulta una técnica idónea para este propósito. Sin embargo, la aplicación de la EIS a la conservación del patrimonio cultural metálico no es una práctica generalizada, por las dificultades particulares que presenta su aplicación en este campo. Las características propias de los bienes culturales, hacen que en muchos casos los estudios de laboratorio no sean suficientes, y que el objeto no se pueda trasladar, por lo que resulta imprescindible la realización de medidas in situ, directamente sobre la superficie del objeto a conservar. La aplicación de técnicas electroquímicas requiere montar una celda electroquímica, en la que poner en contacto la superficie del material que se va a estudiar con un electrólito líquido y los electrodos auxiliares (electrodo de referencia y contraelectrodo). Esta tarea resulta compleja en el caso de superficies irregulares y no horizontales como las de una escultura. Para dar una solución a este problema, el objetivo de esta tesis ha sido el desarrollo de una celda electroquímica con un electrólito en gel, específicamente diseñada para la realización de medidas in situ sobre patrimonio cultural. Para el diseño se han tenido en cuenta diversos factores relacionados con este tipo de medidas, tales como la forma y tamaño de la celda para facilitar su colocación en la superficie de la obra, la naturaleza, geometría y posición de los electrodos para obtener una señal de calidad, o el tipo de soporte adecuado para lograr una buena estabilidad mecánica. El trabajo se ha estructurado en varios apartados, si bien no recorrido su no ha sido lineal, ya que los avances y dificultades en cada uno de los aspectos o subapartados han contribuido al desarrollo de los demás. El primer paso ha sido comprobar la posibilidad de realizar medidas de impedancia utilizando un electrólito gelificado con agar, abordando cuestiones como la validez, reproducibilidad o repetividad de los resultados. Una vez verificada la obtención de medidas de calidad y comparables a las de un electrólito tradicional, se ha estudiado en mayor detalle la contribución del agar en las medidas, para establecer la concentración más adecuada tanto desde el punto de vista electroquímico como mecánico. En esta misma línea, se ha comparado el comportamiento del agar y de la agarosa, uno de los dos polisacáridos que componen este material, y que es el responsable de las propiedades gelificantes. El siguiente paso ha sido analizar en detalle el comportamiento del sistema completo, incluyendo los electrodos (de referencia y contraelectrodo) para optimizar el diseño. Así, se han estudiado diferentes configuraciones de celda con electrodos de distinta naturaleza y geometría, un factor que ha demostrado su relevancia para minimizar la aparición de artefactos en las medidas al emplearse electrólitos de baja conductividad. En paralelo al desarrollo y estudio de la celda, se han realizado medidas sobre diferentes sustratos para evaluar la aplicabilidad del sistema desarrollado a la resolución de problemas de conservación. Por un lado, se han realizado ensayos de laboratorio sobre probetas de bronce y acero patinable con diversas pátinas y recubrimientos, simulando cuestiones que se abordan habitualmente en la conservación del patrimonio metálico; por otro lado, se han realizado estudios in situ, sobre obra real (principalmente escultura moderna y contemporánea del Museo Arqueológico Nacional, Museo de Escultura de Leganés y colección de escultura del campus de la Universidad Politécnica de Valencia), para comprobar y validar el diseño de la celda en su modo de aplicación final, e ir introduciendo las modificaciones necesarias para solventar las dificultades prácticas que se iban encontrando en diferentes situaciones. Todo ello ha permitido concluir con éxito con el diseño de una celda electroquímica con electrólito en gel, adecuada para la realización de medidas electroquímicas in situ sobre el patrimonio cultural metálico, aportando una nueva herramienta para avanzar en la conservación de este tipo de patrimonio.Along history, mankind has sought to preserve certain objects which, for multiple reasons, have acquired a special value and a meaning for the society that owned them, constituting their cultural heritage. In this effort to preserve the past for the present and future generations, scientific research has gained an increasing relevance. Conservation science aims at understanding problems and provide solutions for the conservation of heritage, both from the technological and sustainable point of view. The proper design and planning of strategies for the conservation of cultural heritage objects and collections is essential, and should take into account both technological and resources limitations. The purpose of this thesis is to contribute through Materials Science and Engineering to this objective, in particular in the field of metallic cultural heritage, developing a tool of diagnosis of the state of conservation and evaluation of protection systems for this type of heritage. The main challenge for the conservation of the heritage metal is corrosion, which takes place because of the interaction between the metal object and its environment. To deal with this problem, metal conservators have two strategies: control of environmental conditions - which is not always possible - or the use of protective coatings to isolate the metal object from the environment, which is the most frequent solution in conservation practice. Nonetheless, any method has certain limitations. For this reason, it is of great importance being able to evaluate the effectiveness and lifespan of protective systems before damage occurs. Common coatings in heritage conservation –mainly waxes and acrylic varnishes- have a quite limited protective ability, and have to be renewed periodically. This entails the need of knowing and evaluating the behavior of applied protective coatings, with particular focus on durability. Electrochemical impedance spectroscopy (EIS) is an electrochemical technique that allows to investigate corrosion mechanisms of metals in different environments and to evaluate the protective properties of coatings. This makes EIS the ideal technique for this purpose. Unfortunately, the use of EIS in metal cultural heritage is not a widespread practice, due to the particular difficulties in applying this technique in heritage objects. The special characteristics of cultural heritage assets make it necessary to carry out on site measurements, directly on the surface of the object to preserve. The use of electrochemical techniques requires mounting an electrochemical cell, in which the surface of the material under study is placed in contact with a liquid electrolyte and the auxiliary electrodes (reference and counter electrode). This is not an easy task for irregular and non-horizontal surfaces as in a sculpture. To overcome this challenge, the objective of this thesis is to develop an electrochemical cell with a gelled electrolyte, specifically designed for conducting in situ electrochemical measurements on cultural heritage. The design has taken into account various factors related to this type of measures, such as the shape and size of the cell to be placed on the surface of the object, the nature, geometry and position of the electrodes to obtain a quality signal, or the fixing system to ensure a good mechanical stability. This work has been structured into several sections, although its progress has not been linear in time, since the advances and difficulties in each of the aspects or subsections have contributed to improve and develop the others. The first step has been checking the possibility of performing impedance measures using an agar gelled electrolyte, addressing issues such as validity, reproducibility, or repeatability of the results. Once verified the quality of measurements, comparable to a traditional electrolyte, detail the contribution of the agar been studied in greater detail, to establish the most appropriate concentration both from the electrochemical and mechanical point of view. With the same purpose the behavior of agar and agarose has been compared. The next step was to analyze in detail the behavior of the entire system, including electrodes (reference and counter electrode) to optimize the design. Thus, we have studied different configurations of cell with electrodes of different nature and geometry, a factor that has shown its relevance to minimize the appearance of artifacts in the measurements when using low-conductivity electrolytes. In parallel to the development and study of the cell, measurements on different substrates have been performed to assess the applicability of the developed system to solve conservation problems. On the one hand, laboratory tests on bronze and weathering steel coupons, with different patinas and coatings were performed, simulating issues usually addressed in metallic heritage conservation; on the other hand, studies have been conducted in situ on real work (mainly modern and contemporary sculpture of the National Archaeological Museum, Museum of Sculpture in Leganes and the sculpture collection at the Polytechnic University of Valencia campus), to check and validate the design of the cell in its final application mode, and to introduce the modifications necessary to solve the practical difficulties that were found in different situations. This has allowed concluding successfully with the design of an electrochemical cell with a gel electrolyte, suitable for carrying out on-site electrochemical measures on metallic cultural heritage, providing a new tool for a better conservation of this kind of heritage.El trabajo que aquí se presenta ha sido financiado por la beca FPI BES-2012-052716 y el proyecto HAR2011-22402 del Plan Nacional de I+D+i 2008-2011 del Ministerio de Ciencia e Innovación, el proyecto HAR2014-54893-R, HAR2014-54893-R, la Comunidad de Madrid y el fondo Social Europeo en el marco del Programa Geomateriales 2 (S2013/MIT 2914), y el proyecto IPERION-CH (European Union H2020, G.A. 654028).Programa de Doctorado en Ciencia e Ingeniería de Materiales por la Universidad Carlos III de MadridPresidente: Juan Carlos Galván Sierra.- Secretario: Antonia Jiménez Morales.- Vocal: Kepa Castro Ortiz de Pined

Realistic Aging of Materials in Computer Graphics

One of the most challenging tasks in Computer Graphics (CG) is depicting the accurate appearance of aging and weathered materials. This thesis examines the physical aging process of materials and translates that information into data that can be applied to CG materials resulting in a new prototype system for simulating realistic aging and weathering of CG materials. This new system will enable artists to quickly and accurately generate materials with a realistic appearance of aging and weathering. The resulting user interface generated from this system allows artists to create a variety of realistic and customized layered materials which offers a wide array of complexities. This prototype was then implemented into a studio setting which helped speed up the production process for material generation

A viscous paint model for interactive applications

We present a viscous paint model for use in an interactive painting system based on the well-known Stokes’ equations for viscous flow. Our method is, to our knowledge, the first unconditionally stable numerical method that treats viscous fluid with a free surface boundary. We have also developed a real-time implementation of the Kubelka-Munk reflectance model for pigment mixing, compositing and rendering entirely on graphics hardware, using programmable fragment shading capabilities. We have integrated our paint model with a prototype painting system, which demonstrates the model’s effectiveness in rendering viscous paint and capturing a thick, impasto-like style of painting. Several users have tested our prototype system and were able to start creating original art work in an intuitive manner not possible with the existing techniques in commercial systems

Computer graphics simulation of natural mummification by desiccation

© 2020 The Authors. Computer Animation and Virtual Worlds published by John Wiley & Sons, Ltd. Organic bodies are subject to internal processes after death, causing significant structural, and optical changes. Mummification by desiccation leads to volume shrinkage, skin wrinkling, and discoloration. We propose a method to simulate the process of mummification by desiccation and its effects on the corpse's morphology and appearance. The mummifying body is represented by a layered model consisting of a tetrahedral mesh, representing the volume, plus a high resolution triangle surface mesh representing the skin. The finite element method is used to solve the moisture diffusion and the resulting volume deformations. Skin wrinkling is achieved using position based dynamics. In order to model a visually believable reproduction of the skin coloration changes due to mummification, a skin shading approach is used that considers moisture content, hemoglobin content, and oxygen saturation. The main focus of the work in this article is to recreate the appearance changes of mummification by desiccation, which, to the best of our knowledge, has not been attempted before in computer graphics to this level of realism. The suggested approach is able to model changes in the internal structure and the surface appearance of the body which resemble the postmortem processes of natural mummification by desiccation

Procedural aging techniques of synthetic cities and 3D scenarios

Today we live in an increasingly computerized and demanding world. A world where is constantly presented the need for, the industry of video games and movies, to find ways to create more realistic graphics environments, faster and longer with a huge level of variety. To address this need, the techniques for procedural generation appeared. These techniques were used by the computer graphics industry to create textures to simulate special effects and generate complex natural models, including mostly vegetation. Within these first techniques we can find a wide range of techniques. Subsequently, with the needs to create increasingly more complex and realistic environments, emerged the solution to adapt these algorithms, already known, to something more complex such as the generation of a road infrastructure, the generation of buildings or allowed to practically generate a world only with procedural generation and a set of rules. Although this development is increasingly felt, we noticed there is an interest in a new area, which is the procedural aging of buildings in these graphical worlds. Several authors had proposed to create new and better algorithms of procedural aging in building. These authors when approaching this subject, tend to follow a very unique and specific way, creating an algorithm capable of playing a unique phenomenon of aging. Thus, identified this gap in the literature, it was decided to seize this opportunity and present and develop a procedural aging algorithm applied to buildings that is capable of reproduce different aging phenomena, and that consumes low computational resources being capable of be applied to a huge 3D scenario.Hoje em dia vivemos num mundo cada vez mais computorizado e exigente. Um mundo onde cada vez mais está presente a necessidade de a industria dos jogos de vídeo e dos filmes arranjar maneiras de criar ambientes gráficos mais realistas, mais rapidamente e já com um nível de variedade grande. Para colmatar esta necessidade surgiu então as técnicas de geração procedural. Estas técnicas aliaram-se á industria de computação gráfica para criar texturas naturais, simular efeitos especiais e gerar modelos naturais complexos, incluindo maioritariamente vegetação. Dentro destas primeiras técnicas podemos encontrar as fractais, L-system e Perlin Noise, entre outros. Posteriormente, com a necessidades de criar cada vez mais ambientes mais complexos, surgiu a solução de adaptar estes algoritmos já conhecidos para algo mais complexo, como a geração de uma estrutura rodoviária, ou como a geração de edifícios podendo assim praticamente gerar um mundo inteiro somente com a geração procedural e um conjunto de regras. Apesar de esta evolução ser cada vez mais sentida, notou-se um crescente interesse num tema em partcular, sendo essa, o envelhecimento procedural dos edifícios nestes mundos gráficos. Vários autores até então tinham-se proposto a criar novos e cada vez melhores algoritmos de envelhecimento procedural dos edifícios. Estes autores ao abordar este tema, tendem em seguir um caminho muito singular e especifico, criando um algoritmo capaz de reproduzir um unico fenomeno de envelhecimento. Assim, identificada esta lacuna na literatura, decidiu-se agarrar esta oportunidade e apresentar e desenvolver um algoritmo de envelhecimento procedural aplicado aos edifícios que é capaz de reproduzir diferentes fenomenos de envelhecimento, e que consome poucos recursos computacionais sendo capaz de ser aplicado a um grande cenário 3D