MeshPipe: a Python-based tool for easy automation and demonstration of geometry processing pipelines

The popularization of inexpensive 3D scanning, 3D printing, 3D publishing and AR/VR display technologies have renewed the interest in open-source tools providing the geometry processing algorithms required to clean, repair, enrich, optimize and modify point-based and polygonal-based models. Nowadays, there is a large variety of such open-source tools whose user community includes 3D experts but also 3D enthusiasts and professionals from other disciplines. In this paper we present a Python-based tool that addresses two major caveats of current solutions: the lack of easy-to-use methods for the creation of custom geometry processing pipelines (automation), and the lack of a suitable visual interface for quickly testing, comparing and sharing different pipelines, supporting rapid iterations and providing dynamic feedback to the user (demonstration). From the user's point of view, the tool is a 3D viewer with an integrated Python console from which internal or external Python code can be executed. We provide an easy-to-use but powerful API for element selection and geometry processing. Key algorithms are provided by a high-level C library exposed to the viewer via Python-C bindings. Unlike competing open-source alternatives, our tool has a minimal learning curve and typical pipelines can be written in a few lines of Python code.Peer ReviewedPostprint (published version

Single-picture reconstruction and rendering of trees for plausible vegetation synthesis

State-of-the-art approaches for tree reconstruction either put limiting constraints on the input side (requiring multiple photographs, a scanned point cloud or intensive user input) or provide a representation only suitable for front views of the tree. In this paper we present a complete pipeline for synthesizing and rendering detailed trees from a single photograph with minimal user effort. Since the overall shape and appearance of each tree is recovered from a single photograph of the tree crown, artists can benefit from georeferenced images to populate landscapes with native tree species. A key element of our approach is a compact representation of dense tree crowns through a radial distance map. Our first contribution is an automatic algorithm for generating such representations from a single exemplar image of a tree. We create a rough estimate of the crown shape by solving a thin-plate energy minimization problem, and then add detail through a simplified shape-from-shading approach. The use of seamless texture synthesis results in an image-based representation that can be rendered from arbitrary view directions at different levels of detail. Distant trees benefit from an output-sensitive algorithm inspired on relief mapping. For close-up trees we use a billboard cloud where leaflets are distributed inside the crown shape through a space colonization algorithm. In both cases our representation ensures efficient preservation of the crown shape. Major benefits of our approach include: it recovers the overall shape from a single tree image, involves no tree modeling knowledge and minimal authoring effort, and the associated image-based representation is easy to compress and thus suitable for network streaming.Peer ReviewedPostprint (author's final draft

Assessment on the Efficiency of an Active Solar Thermal Facade: Study of the Effect of Dynamic Parameters and Experimental Analysis When Coupled/Uncoupled to a Heat Pump

The building sector presents poor performance in terms of energy efficiency and is looking for effective alternatives aimed at reducing the use of fossil fuels. The facade is a key element able to harness renewable energy as an Active Solar Thermal Facade (ASTF). The main purpose of this study is the assessment of a novel design concept based on a steel sandwich panel technology. The performance of the active system will be first addressed by a parametric study in order to analyze its behavior and secondly, by describing a real case based on an experimental test by connecting the active panels to a heat pump. The study shows the impact of solar irradiation and mass flow on the thermal jump achieved, while ambient and fluid inlet temperatures are the most influencing parameters in the efficiency of the facade. When coupled to the heat pump, results from a measurement campaign demonstrate a remarkable improvement in the performance of the ASTF. The results presented provide significant proof about the benefits of a synergetic combination of both technologies—solar facades and heat pumps—as efficient alternatives for the building sector, aiming to improve energy efficiency as well as reduce their dependence on non-renewable sources.This research was partially funded by the Basque Government through IT781-13 and IT1314-19 research groups and by the University of the Basque Country UPV/EHU through PES17/25. Additionally, TECNALIA Research & Innovation supported the research activities research through a cooperation agreement (PT10516) with UPV/EHU

Parametric assessment of a building active façade by means of a combined metallic sandwich panel with an unglazed solar collector

The building sector has a poor performance in terms of energy efficiency and is looking for alternatives to reduce the use of fossil fuels on building use stage. Renewables are unlimited and solar thermal energy is a technology with a demonstrated potential. The façade is a key element able to harness renewable energy coming from the sun becoming in an Active Solar Thermal Façade (ASTF). The main purpose of this study is the development of a parametric study using a numerical model to analyze the behavior of an unglazed solar collector. Thus, evaluating different design and meteorological parameters to show their influence on the heat transfer and the efficiency. The study shows that solar irradiation and mass flow are the most influential on thermal difference. However, for the efficiency ambient temperature and inlet temperature both are the most influencing ones. In brief, a set of parameters have a significant influence on the behavior of the ASTF that are fully governed by environmental conditions. Nevertheless, there are some other parameters that can be controlled during the operation. The challenge is to make a continuous configuration of this adaptable values depending on the external situation to achieve a higher performance for the ASTF

La emigración cualificada española en Francia y Alemania

A pesar del interés que despierta el fenómeno de las migraciones cualificadas, es difícil encontrar datos que permitan realizar un análisis detallado de los factores que condicionan la movilidad. El caso español constituye un ejemplo de la modificación cualitativa en la composición de las migraciones de sur a norte en Europa tras el ingreso en la Comunidad Económica Europea. No se produjeron migraciones masivas de trabajadores sin cualificación; sin embargo, sí se alteró drásticamente su composición: la migración no cualificada fue sustituida por migración cualificada de España a Alemania y Francia. Esta migración queda ocultada por la llegada masiva de inmigrantes a España. Empleando los datos de la encuesta EIMSS, se analizan las diferencias de las condiciones de egreso y movilidad entre los dos tipos de migrantes, cualificados y no cualificados.Despite the interest in the phenomenon of migration, it is difficult to find qualified data which allows for a detailed analysis of the factors upon which this mobility is conditioned. The Spanish case shows an important example of qualitative modification in the composition of migrations from the south to the north of Europe since Spain's introduction into the European Community. No mass migration of low skilled workers was experienced. Nonetheless, the composition underwent drastic changes: The migration of low skilled workers was replaced by that of highly skilled workers from Spain to Germany and France. This migration went unnoticed due to the mass arrival of immigrants in Spain. An analysis was made of the differences in the conditions of migration and mobility between the two types of migrants, highly and low skilled, using the data obtained in the EIMSS survey

Triangle influence supersets for fast distance computation

We present an acceleration structure to efficiently query the Signed Distance Field (SDF) of volumes represented by trianglemeshes. The method is based on a discretization of space. In each node, we store the triangles defining the SDF behaviour inthat region. Consequently, we reduce the cost of the nearest triangle search, prioritizing query performance, while avoidingapproximations of the field. We propose a method to conservatively compute the set of triangles influencing each node. Given anode, each triangle defines a region of space such that all points inside it are closer to a point in the node than the triangle is.This property is used to build the SDF acceleration structure. We do not need to explicitly compute these regions, which is crucialto the performance of our approach. We prove the correctness of the proposed method and compare it to similar approaches,confirming that our method produces faster query times than other exact methods.This work has been partially funded by Ministeri de Ciència i Innovació (MICIN), Agencia Estatal de Investigación (AEI) and the Fons Europeu de Desenvolupament Regional (FEDER) (project PID2021-122136OB-C21 funded by MCIN/AEI/10.13039/501100011033/FEDER, UE). The first author gratefully acknowledges the Universitat Politècnica de Catalunya and Banco Santander for the financial support of his predoctoral grant FPI-UPC grant.Peer ReviewedPostprint (published version

Adaptive approximation of signed distance fields through piecewise continuous interpolation

In this paper, we present an adaptive structure to represent a signed distance field through trilinear or tricubic interpolation of values, and derivatives, that allows for fast querying of the field. We also provide a method to decide when to subdivide a node to achieve a provided threshold error. Both the numerical error control, and the values needed to build the interpolants, require the evaluation of the input field. Still, both are designed to minimize the total number of evaluations. C0 continuity is guaranteed for both the trilinear and tricubic version of the algorithm. Furthermore, we describe how to preserve C1 continuity between nodes of different levels when using a tricubic interpolant, and provide a proof that this property is maintained. Finally, we illustrate the usage of our approach in several applications, including direct rendering using sphere marching.This work has been partially funded by Ministeri de Ciència i Innovació (MICIN), Agencia Estatal de Investigación (AEI) and the Fons Europeu de Desenvolupament Regional (FEDER) (project PID2021-122136OB-C21 funded by MCIN/AEI/10.13039/501100011033/FEDER, UE). The first author gratefully acknowledges the Universitat Politècnica de Catalunya and Banco Santander for the financial support of his predoctoral grant FPI-UPC grant.Peer ReviewedPostprint (published version

Zeolites: Promised Materials for the Sustainable Production of Hydrogen

Zeolites have been shown to be useful catalysts in a large variety of reactions, from acid to base and redox catalysis. ð£e particular properties of these materials (high surface area, uniform porosity, interconnected pore/channel system, accessible pore volume, high adsorption capacity, ion-exchange ability, and shape/size selectivity) provide crucial features as effective catalysts and catalysts supports. Currently, new applications are being developed from the considerable existing knowledge about these important and remarkable materials. Among them, those applications related to the development of processes with less impact on the environment (green processes) and with the production of alternative and cleaner energies are of paramount importance. Hydrogen is believed to be critical for the energy and environmental sustainability. It is a clean energy carrier which can be used for transportation and stationary power generation. In the production of hydrogen, the development of new catalysts is one of the most important and effective ways to address the problems related to the sustainable production of hydrogen. ð£is paper explores the possibility to use zeolites as catalysts or supports of catalysts to produce hydrogen from renewable resources. Speci􀄕cally, two approaches have been considered: reforming of biomass-derived compounds (reforming of bioethanol) and water splitting using solar energy. ð£is paper examines the role of zeolites in the preparation of highly active and selective ethanol steam reforming catalysts and their main properties to be used as efficient water splitting photocatalysts.Chica, A. (2013). Zeolites: Promised Materials for the Sustainable Production of Hydrogen. ISRN Chemical Engineering. (907425):1-19. doi:10.1155/2013/907425S119907425Barrer, R. M., & Ibbitson, D. A. (1944). Occlusion of hydrocarbons by chabazite and analcite. 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M., Sánchez-Sánchez, M. C., Alvarez-Galvan, M. C., Valle, F. del, & Fierro, J. L. G. (2009). Hydrogen production from renewable sources: biomass and photocatalytic opportunities. Energy Environ. Sci., 2(1), 35-54. doi:10.1039/b808138gVaidya, P. D., & Rodrigues, A. E. (2006). Insight into steam reforming of ethanol to produce hydrogen for fuel cells. Chemical Engineering Journal, 117(1), 39-49. doi:10.1016/j.cej.2005.12.008Kolios, G., Glöckler, B., Gritsch, A., Morillo, A., & Eigenberger, G. (2005). Heat-Integrated Reactor Concepts for Hydrogen Production by Methane Steam Reforming. Fuel Cells, 5(1), 52-65. doi:10.1002/fuce.200400065Haryanto, A., Fernando, S., Murali, N., & Adhikari, S. (2005). Current Status of Hydrogen Production Techniques by Steam Reforming of Ethanol:  A Review. Energy & Fuels, 19(5), 2098-2106. doi:10.1021/ef0500538Ni, M., Leung, D. Y. C., & Leung, M. K. H. (2007). A review on reforming bio-ethanol for hydrogen production. International Journal of Hydrogen Energy, 32(15), 3238-3247. doi:10.1016/j.ijhydene.2007.04.038FATSIKOSTAS, A. (2004). Reaction network of steam reforming of ethanol over Ni-based catalysts. Journal of Catalysis, 225(2), 439-452. doi:10.1016/j.jcat.2004.04.034Llorca, J., Piscina, P. R. de la, Sales, J., & Homs, N. (2001). Direct production of hydrogen from ethanolic aqueous solutions over oxide catalysts. Chemical Communications, (7), 641-642. doi:10.1039/b100334hDiagne, C., Idriss, H., & Kiennemann, A. (2002). Hydrogen production by ethanol reforming over Rh/CeO2–ZrO2 catalysts. Catalysis Communications, 3(12), 565-571. doi:10.1016/s1566-7367(02)00226-1Llorca, J., de la Piscina, P. R., Dalmon, J.-A., Sales, J., & Homs, N. (2003). CO-free hydrogen from steam-reforming of bioethanol over ZnO-supported cobalt catalysts. Applied Catalysis B: Environmental, 43(4), 355-369. doi:10.1016/s0926-3373(02)00326-0Batista, M. S., Santos, R. K. ., Assaf, E. M., Assaf, J. M., & Ticianelli, E. A. (2004). High efficiency steam reforming of ethanol by cobalt-based catalysts. Journal of Power Sources, 134(1), 27-32. doi:10.1016/j.jpowsour.2004.01.052Kaddouri, A., & Mazzocchia, C. (2004). A study of the influence of the synthesis conditions upon the catalytic properties of Co/SiO2 or Co/Al2O3 catalysts used for ethanol steam reforming. Catalysis Communications, 5(6), 339-345. doi:10.1016/j.catcom.2004.03.008Llorca, J., Dalmon, J.-A., Ramı́rez de la Piscina, P., & Homs, N. (2003). In situ magnetic characterisation of supported cobalt catalysts under steam-reforming of ethanol. Applied Catalysis A: General, 243(2), 261-269. doi:10.1016/s0926-860x(02)00546-xIdriss, H. (2004). Ethanol Reactions over the Surfaces of Noble Metal/Cerium Oxide Catalysts. Platinum Metals Review, 48(3), 105-115. doi:10.1595/147106704x1603Bussi, J., Bespalko, N., Veiga, S., Amaya, A., Faccio, R., & Abello, M. C. (2008). The preparation and properties of Ni–La–Zr catalysts for the steam reforming of ethanol. Catalysis Communications, 10(1), 33-38. doi:10.1016/j.catcom.2008.07.028Sun, G. B., Hidajat, K., Wu, X. S., & Kawi, S. (2008). A crucial role of surface oxygen mobility on nanocrystalline Y2O3 support for oxidative steam reforming of ethanol to hydrogen over Ni/Y2O3 catalysts. Applied Catalysis B: Environmental, 81(3-4), 303-312. doi:10.1016/j.apcatb.2007.12.021PEREIRA, E., HOMS, N., MARTI, S., FIERRO, J., & RAMIREZDELAPISCINA, P. (2008). Oxidative steam-reforming of ethanol over Co/SiO2, Co–Rh/SiO2 and Co–Ru/SiO2 catalysts: Catalytic behavior and deactivation/regeneration processes. Journal of Catalysis, 257(1), 206-214. doi:10.1016/j.jcat.2008.05.001Fajardo, H. V., Probst, L. F. D., Carreño, N. L. V., Garcia, I. T. S., & Valentini, A. (2007). Hydrogen Production from Ethanol Steam Reforming Over Ni/CeO2 Nanocomposite Catalysts. Catalysis Letters, 119(3-4), 228-236. doi:10.1007/s10562-007-9222-6Cavallaro, S. (2000). Ethanol Steam Reforming on Rh/Al2O3Catalysts. Energy & Fuels, 14(6), 1195-1199. doi:10.1021/ef0000779Fierro, V., Klouz, V., Akdim, O., & Mirodatos, C. (2002). Oxidative reforming of biomass derived ethanol for hydrogen production in fuel cell applications. Catalysis Today, 75(1-4), 141-144. doi:10.1016/s0920-5861(02)00056-1Velu, S., Satoh, N., Gopinath, C. S., & Suzuki, K. (2002). Catalysis Letters, 82(1/2), 145-152. doi:10.1023/a:1020516830768Goula, M. A., Kontou, S. K., & Tsiakaras, P. E. (2004). Hydrogen production by ethanol steam reforming over a commercial Pd/γ-Al2O3 catalyst. Applied Catalysis B: Environmental, 49(2), 135-144. doi:10.1016/j.apcatb.2003.12.001Sheng, P. Y., & Idriss, H. (2004). Ethanol reactions over Au–Rh/CeO2 catalysts. Total decomposition and H2 formation. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 22(4), 1652-1658. doi:10.1116/1.1705591Srinivas, D., Satyanarayana, C. V. V., Potdar, H. S., & Ratnasamy, P. (2003). Structural studies on NiO-CeO2-ZrO2 catalysts for steam reforming of ethanol. Applied Catalysis A: General, 246(2), 323-334. doi:10.1016/s0926-860x(03)00085-1Galvita, V. V., Belyaev, V. D., Semikolenov, V. A., Tsiakaras, P., Frumin, A., & Sobyanin, V. A. (2002). Reaction Kinetics and Catalysis Letters, 76(2), 343-351. doi:10.1023/a:1016500431269Platon, A., Roh, H.-S., King, D. L., & Wang, Y. (2007). Deactivation Studies of Rh/Ce0.8Zr0.2O2 Catalysts in Low Temperature Ethanol Steam Reforming. Topics in Catalysis, 46(3-4), 374-379. doi:10.1007/s11244-007-9007-6Birot, A., Epron, F., Descorme, C., & Duprez, D. (2008). Ethanol steam reforming over Rh/CexZr1−xO2 catalysts: Impact of the CO–CO2–CH4 interconversion reactions on the H2 production. Applied Catalysis B: Environmental, 79(1), 17-25. doi:10.1016/j.apcatb.2007.10.002CAI, W., WANG, F., ZHAN, E., VANVEEN, A., MIRODATOS, C., & SHEN, W. (2008). 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Image-based tree variations

The automatic generation of realistic vegetation closely reproducing the appearance of specific plant species is still a challenging topic in computer graphics. In this paper, we present a new approach to generate new tree models from a small collection of frontal RGBA images of trees. The new models are represented either as single billboards (suitable for still image generation in areas such as architecture rendering) or as billboard clouds (providing parallax effects in interactive applications). Key ingredients of our method include the synthesis of new contours through convex combinations of exemplar countours, the automatic segmentation into crown/trunk classes and the transfer of RGBA colour from the exemplar images to the synthetic target. We also describe a fully automatic approach to convert a single tree image into a billboard cloud by extracting superpixels and distributing them inside a silhouette-defined 3D volume. Our algorithm allows for the automatic generation of an arbitrary number of tree variations from minimal input, and thus provides a fast solution to add vegetation variety in outdoor scenes.Peer ReviewedPostprint (author's final draft

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Despite the large amount of methods and applications of augmented reality, there is little homogenization on the software platforms that support them. An exception may be the low level control software that is provided by some high profile vendors such as Qualcomm and Metaio. However, these provide fine grain modules for e.g. element tracking. We are more concerned on the application framework, that includes the control of the devices working together for the development of the AR experience. In this paper we present a software framework that can be used for the development of AR applications based on camera-projector pairs, that is suitable for both fixed, and nomadic setups.Peer ReviewedPostprint (author's final draft