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3D4LIFE Journals Results
Bosch, Carles; Patow, Gustavo A.
Computer Graphics Forum, Vol. 38, Num. 1, pp 274-285, 2019.
DOI: http://dx.doi.org/10.1111/cgf.13530
Abstract Modelling flow phenomena and their related weathering effects is often cumbersome due their dependence on the environment, materials and geometric properties of objects in the scene. Example-based modelling provides many advantages for reproducing real textures, but little effort has been devoted to reproducing and transferring complex phenomena. In order to produce realistic flow effects, it is possible to take advantage of the widespread availability of flow images on the Internet, which can be used to gather key information about the flow. In this paper, we present a technique that allows the transfer of flow phenomena between photographs, adapting the flow to the target image and giving the user flexibility and control through specifically tailored parameters. This is done through two types of control curves: a fitted theoretical curve to control the mass of deposited material, and an extended colour map for properly adapting to the target appearance. In addition, our method filters and warps the input flow in order to account for the geometric details of the target surface. This leads to a fast and intuitive approach to easily transfer phenomena between images, providing a set of simple and intuitive parameters to control the process.
A procedural technique for thermal simulation and visualization in urban environments
Muñoz, David; Besuievsky, Gonzalo; Patow, Gustavo A.
Building Simulation, 2019.
DOI: http://dx.doi.org/10.1007/s12273-019-0549-x
Analysing the thermal behaviour of buildings is an important goal for any and all of the tasks involving energy flow simulation in urban environments. However, the number of variables to be considered, along with the difficulty of implementing some of them, make it difficult to address the problem on an urban scale. In this paper we propose a procedural approach that, from a 3D urban model and a set of parameters, simulates the thermal exchanges that take place inside and outside buildings in an urban environment. We also provide a technique to efficiently visualise thermal variations over time of both the interior and exterior of buildings in an urban environment. We believe this technique will be helpful for performing a rapid analysis when building parameters, such as materials, dimensions, shape or number of floors, are being changed.
Diego Jesus; Patow, Gustavo A.; António Coelho; António Augusto Sousa
Computers & Graphics, Vol. 72, pp 106-121, 2018.
DOI: http://dx.doi.org/10.1016/j.cag.2018.02.003
Procedural modeling techniques reduce the effort of creating large virtual cities. However, current methodologies do not allow direct user control over the generated models. Associated with this problem, we face the additional problem related to intrinsic ambiguity existing in user selections. In this paper, we propose to address this problem by using a genetic algorithm to generalize user-provided point-and-click selections of building elements. From a few user-selected elements, the system infers new sets of elements that potentially correspond to the user’s intention, including the ones manually selected. These sets are obtained by queries over the shape trees generated by the procedural rules, thus exploiting shape semantics, hierarchy and geometric properties. Our system also provides a complete selection-action paradigm that allows users to edit procedurally generated buildings without necessarily explicitly writing queries. The pairs of user selections and procedural operations (the actions) are stored in a tree-like structure, which is easily evaluated. Results show that the selection inference is capable of generating sets of shapes that closely match the user intention and queries are able to perform complex selections that would be difficult to achieve in other systems. User studies confirm this result.
Mas, Albert; Martí­n, Ignacio; Patow, Gustavo A.
Computers & Graphics, Vol. 77, pp 1 - 15, 2018.
DOI: http://dx.doi.org/10.1016/j.cag.2018.09.010
This paper presents a global optimization algorithm specifically tailored for inverse reflector design problems. In such problems, the goal is to obtain a reflector shape that produces a light distribution as close as possible to a user-provided one. The optimization is an iterative process where each step evaluates the difference between the current reflector illumination and the desired one. We propose a tree-based stochastic method that drives the optimization process, using some heuristic rules, to reach a minimum below a user-provided threshold that satisfies the requirements. When we are close to the solution, we resort to the Hooke and Jeeves method, to reach the minimum faster. Extending our previous work Mas et al. (2010), we show that our method reaches a solution in fewer steps than most other classic optimization methods, and also avoids many local minima. The method has been tested on a real case study based on European road lighting safety regulations.
3D4LIFE Conferences Results
A Level-of-Detail Technique for Urban Physics Calculations in Large Urban Environments
Muñoz, David; Besuievsky, Gonzalo; Patow, Gustavo A.
Spanish Computer Graphics Conference (CEIG), pp 09-17, 2019.
DOI: http://dx.doi.org/10.2312/ceig.20191198
In many applications, such as urban physics simulations or the study of the solar impact effects at different scales, complex 3D city models are required to evaluate physical values. In this paper we present a new technique which, through the use of an electrical analogy and the calculation of sky view factors and form factors, allows to simulate and study the thermal behaviour of an urban environment, taking into account the solar and sky radiation, the air and sky temperatures, and even the thermal interaction between nearby buildings. We also show that it is possible, from a 3D recreation of a large urban environment, to simulate the heat exchanges that take place between the buildings of a city and its immediate surroundings. In the same way, taking into account the terrestrial zone, the altitude and the type of climate with which the simulations are carried out, it is possible to compare the thermal behaviour of a large urban environment according to the chosen conditions.
LeoMCAD: A Lego-based Mechanical CAD system
Gonzalez, Francisco; Jesús Amador Pérez; Patow, Gustavo A.
Spanish Computer Graphics Conference (CEIG), 2018.
DOI: http://dx.doi.org/10.2312/ceig.20181163
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Mechanical Design (MCAD) tools are used for creating 3D digital prototypes used in the design, visualization, and simulation of products. In this paper we present LeoMCAD, a Lego-based mechanical system designed to be used as an education tool both for kids and Lego hobbyists; but which features a novel solver that naturally and seamlessly computes the interaction between the pieces that build-up a given model, solving an otherwise complex forward kinematic system of equations in a much simpler way. The results show how our system is able to cope with situations that would produce dead-lock situations in more advanced commercial systems.
3D4life PhD Thesis Results