Publications
Advancing racial equity in Brazil’s academia (Sciense -2022)
Willams Oliveira, Bruno E. Soares, Piatã Marques, Caroline Souza, Arildo S. Dias, Marianne Bello, Lis Custódio
People in Brazil who identify as Black, including those with major African inheritance and those who belong to mixed-raced ethnic groups, have historically been underrepresented in postsecondary education as a result of racial and socioeconomic inequities. In Brazil, public universities are free but highly competitive, favoring students from wealthier families who generally had access to better, private secondary education. Black activism in Brazil has highlighted the inadequate access to edu-cation and stimulated debates on how to apply antiracist strategies to achieve racial equity. In 2013, the Labour Party established race-conscious affirmative actions in public universities, which provided aid to low-income Black people, a change that greatly increased the number of Black undergraduate and graduate students. However, President Jair Bolsonaro’s opposition to race-based affirmative action and hostility toward higher education jeopardize these successful measures. The Bolsonaro administration’s budget cuts to science and education limit the funding available for programs that advance diversity in academia by subsidizing housing, food, and transportation for low-income public university students, many of whom are Black. Given the success of affirmative action policies in improving racial equity in Brazilian universities, such programs should be maintained and expanded rather than cut. If decision-makers do not reevaluate this budget, Black people and other minorities will likely be pushed out of academia, and Brazil will lose a generation of bright, underrepresented scientists.As Black scholars who lived through the paradigm shift toward racial equality in higher education in Brazil, we express our profound concerns about the dismantlement of diversity initiatives in postsecondary education. We also demand urgent attention from lawmakers to proposed legislation PL 1788/21, currently under consideration by the Chamber of Deputies, that would maintain racial quotas in higher education for 10 more years. It is urgent to bring this discussion to light; without race-conscious and socioeconomic affirmative actions in the next few years, Brazil will likely face an unprecedented setback in racial equity in academia
Development of an Interactive Tourist Guide (REIC - Revista Eletrônica de Iniciação Científica em Computação - 2020)
Lucas Freitas, Lis Custódio
Abstract: Nowadays, tourists who want to visit small towns find it difficult to get to know the local sights. There is a lot of information spread across websites and social media making it difficult to quickly and objectively obtain relevant information. This difficulty becomes even greater when the desired destinations are small towns without investment in the local tourism. Using only one simple table containing the data about the tourist points of a certain region, our method is able to generate in an automated way an interactive visualization of the tourist places of that region, where you can navigate simply and intuitively to get information on local attractions and, according to user preferences, get a roadmap of attractions to see near your location. The proposed application was evaluated through a study carried out with possible users, which showed positive results regarding usability, ease of learning and satisfaction.
An Extended Triangulation to the Marching Cubes 33 Algorithm ( Journal of the Brazilian Computer Society - 2019 )
Custódio, L., Pesco, S., Silva, C.
Abstract: The Marching Cubes algorithm is arguably the most popular isosurface extraction algorithm. Since its inception, two problems have lingered, namely, triangle quality and topology correctness. Although there is an extensive literature to solve them, topology correctness is achieved in detriment of triangle quality and vice-versa. In this paper we present an extended version of the Marching Cubes 33 algorithm (a variation of the Marching Cubes algorithm which guarantees topological correctness), called Extended Marching Cubes 33. In the proposed algorithm the grid vertex are labeled with "+", "-" and "=", according to the relationship between its scalar eld value and the isovalue. The inclusion of the "=" grid vertex label naturally avoids degenerate triangles. As an application of our method, we use the proposed triangulation to improve the quality of the triangles in the generated mesh while preserving its topology as much as possible.
Derivation of Mean Value Coordinates Using Interior Distance And Their Applicaction on Mesh Deformation (Revista de Informática Teórica e Aplicada - 2018)
Custodio, L., Pesco, S.
Abstract: The deformation methods based on cage controls became a subject of considerable interest due its simplicity and intuitive results. In this technique, the model is enclosed within a simpler mesh (the cage) and its points are expressed as function of the cage elements. Then, by manipulating the cage, the respective deformation is obtained on the model in its interior. In this direction, in the last years, extensions of barycentric coordinates, such as Mean Value coordinates, Positive Mean Value Coordinates, Harmonic coordinates and Green's coordinates, have been proposed to write the points of the model as a function of the cage elements. The Mean Value coordinates, proposed by Floater in two dimensions and extended later to three dimensions by Ju et al. and also by Floater, stands out from the other coordinates because of their simple derivation. However the existence of negative coordinates in regions bounded by non-convex cage control results in a unexpected behavior of the deformation in some regions of the model. In this work, we propose a modification in the derivation of Mean Value Coordinates proposed by Floater. Our derivation maintains the simplicity of the construction of the coordinates and eliminates the undesired behavior in the deformation by diminishing the negative influence of a control vertex on regions of the model not related to it. We also compare the deformation generated with our coordinates and the deformations obtained with the original Mean Value coordinates and Harmonic coordinates.
Desenvolvimento de Ferramenta Computacional para o Ensino e Aprendizagem do Cálculo Numérico (ETARSERRA - 2016)
Almeida, V., Custodio, L.
Resumo:A busca pela motivação para o processo de ensino-aprendizagem nos faz refletir e questionar sobre as ferramentas didáticas que temos utilizado. O desenvolvimento de ferramentas educacionais adequadas para o auxílio no processo de aprendizagem nos cursos de graduação dará condições para que o estudante prossiga na construção do seu conhecimento de forma cooperativa. Neste trabalho propomos uma ferramenta computacional para o auxílio no ensino e aprendizagem da disciplina Cálculo Numérico.
A Evolução do Algoritmo Marching Cubes (Proceeding Series of the Brazilian Society of Computational and Applied Mathematics - 2016)
Custodio, L. e Pesco, S.
Resumo: O algoritmo Marching Cubes, é sem dúvida o mais popular entre os algoritmos de extração de isosuperfície, e uma importante ferramenta para muitos pesquisadores e especialistas em visualização. A adoção generalizada do Marching Cubes resultou em um grande número de melhorias em seu algoritmo ao longo dos anos. Neste trabalho apresentamos uma revisão sobre a evolução do algoritmo Marching Cubes, destacando as principaiscontribuições relacionadas à continuidade e coerência topológica da malha resultante.
Fast Adaptive Blue Noise on Polygonal Surfaces (Graphical Models - 2014)
Medeiros, E., Custodio, L., Pesco, S. and Silva, C. T.
Abstract: This paper proposes a novel method for the computation of hierarchical Poisson disk samplings on polygonal surfaces. The algorithm generates a pointerless hierarchical structure such that each level is a uniform Poisson disk sampling and a subset of the next level. As the main result, given a dynamically-varying importance sampling function defined over a surface, the hierarchy is capable of generating adaptive samplings with blue noise characteristics, temporal-coherence and real-time computation. Classical algorithms produce hierarchies in tight ratios, which is a serious bottleneck specially for a large number of samples. Instead, our method uses sparse ratios and decreases the adaptation error of the hierarchy through a fast optimization process. Therefore, we save a considerable amount of time (up to 74% in our experiments) while preserving the good blue noise properties. We present applications on Non Photo Realistic rendering (NPR), more specifically, on surface stippling effects. First, we apply our method by taking illumination to be the importance sampling to shade the surface, and second, we dynamically deform a surface with a predefined stippled texture.
Practical considerations on Marching Cubes 33 topological correctness (Computer and Graphics - 2013)
Custodio, L., Etiene, T., Pesco, S. and Silva, C. T.
Abstract: Chernyaev's Marching Cubes 33 is one of the first algorithms intended to preserve the topology of the trilinear interpolant. In this work, we address three issues with the Marching Cubes 33 algorithm, two of which are related to its original description and one that is related to its variant. In particular, we solve a problem with the core disambiguation procedure of Marching Cubes 33 that prevents the extraction of topologically correct isosurfaces for the ambiguous configuration 13.5. This work closes an existing gap in the topological correctness of Marching Cubes 33. Furthermore, we make our results reproducible, meaning that examples provided in this work can be easily explored and studied. Finally, as part of the philosophy of reproducibility, we provide a corrected version of the Marching Cubes 33 open-source implementation and access to datasets that can be used to verify the correctness of any available topologically correct isosurface extraction implementation that preserves the topology of the trilinear interpolant.
Extensões de Coordenadas Baricêntricas para Deformação de Malhas (Sibgrapi - Workshop of Theses and Dissertations - 2011)
This work received the best Computer Graphics M.Sc. dissertation award.
Custodio, L., Lewiner, T., Pesco, S.
Abstract: In recent years there has been an increased interest in the use of closed polyhedral cages for surface deformation in three dimensions. The main proposed methods represent the surface points as a linear combination of elements of the cage In this work, we propose a modification of Mean Value Coordinates (MVC) proposed by Floater, in order to maintain the simplicity of construction and eliminate the problems caused by negative coordinates in regions bounded by non- convex polyhedra.
Tuning manifold harmonics filters - (Sibgrapi - XXIII Conference on Graphics, Patterns and Images - 2010)
Thomas Lewiner, Thales Vieira, Alex Bordignon, Allyson Cabral, Clarissa Marques, João Paixão, Lis Custódio, Marcos Lage, Maria Andrade, Renata Nascimento, Scarlett de Botton, Sinésio Pesco, Hélio Lopes, Vinícius Mello, Adelailson Peixoto, Dimas Martinez
Abstract: There are several techniques for automatic music visualization, which are included with virtually any media player. The basic ingredient of those techniques is spectral analysis of the sound, used to automatically generate parameters for procedural image generation. However, only a few music visualizations rely on 3d models. This paper proposes to use spectral mesh processing techniques, namely manifold harmonics, to produce 3d music visualization. The images are generated from 3d models by deforming an initial shape, mapping the sound frequencies to the mesh harmonics. A concise representation of such frequency mapping is proposed to permit for an animated gallery interface with genetic reproduction. Such galleries allow the user to quickly navigate between visual effects. Rendering such animated galleries in real-time is a challenging task, since it requires computing and rendering the deformed shapes at a very high rate. This paper introduces a direct GPU implementation of manifold harmonics filters, which allows to display animated gallery.
An interactive version of Triangle Centers Encyclopedia (IV Colloquium of History and Technology in Mathematics Teaching, Rio de Janeiro, Brazil - 2008)
Bortolossi, H. J., Custódio, L., Dias, S. M. M.
Resumo: Na escola aprendemos que as três medianas de um triângulo sempre se encontram em um mesmo ponto: o baricentro do triângulo. Outros pontos conhecidos desde a Grécia Antiga são o ortocentro, o circuncentro e o incentro. Com o passar do tempo, uma série de propriedades, lugares geométricos e centros do triângulo foram descobertos. Nas últimas décadas, usando coordenadas baricêntricas, o pesquisador Clark Kimberling criou uma enciclopédia com mais de 3000 destes pontos especiais, listando suas propriedades algébricas, mas sem figuras. Neste trabalho apresentamos uma versão visual e interativa desta enciclopédia, construída com o auxílio do software de geometria dinâmica gratuito Régua e Compasso.