ABSTRACT Different quality metrics have been proposed in the literature to evaluate how well a vi... more ABSTRACT Different quality metrics have been proposed in the literature to evaluate how well a visualization represents the underlying data. In this paper, we present a new information-theoretic framework that quantifies the information transfer between the source data set and the rendered image. This approach is based on the definition of an observation channel whose input and output are given by the intensity values of the volumetric data set and the pixel colors, respectively. From this channel, the mutual information, a measure of information transfer or correlation between the input and the output, is used as a metric to evaluate the visualization quality. The usefulness of the proposed observation channel is illustrated with three fundamental visualization applications: selection of informative viewpoints, transfer function design, and light positioning.
To evaluate diffusion anisotropy from diffusion tensor imaging using new measures derived from He... more To evaluate diffusion anisotropy from diffusion tensor imaging using new measures derived from Hellinger divergences and from compositional data distances. New anisotropy measures obtained from the diffusion tensor imaging were measured and compared with classic ones such as fractional anisotropy (FA) and relative anisotropy (RA). The evaluation was done using the three-phase plot (3P-plot). The measures were compared with regard to their sensitivity to detect white and gray matter changes on human DTI data acquired from five normal volunteers. For each volunteer, different volumes of interest located in white matter (WM) and gray matter (GM) were considered. The proposed Compositional Kullback-Leibler (KLA) and the classic FA had a similar behavior, although KLA detected better the transitions between white and gray matter. Moreover, KLA showed a better discrimination in areas with great confluence of fibers. KLA detects better than FA the difference between WM and GM. This leads KLA to be a good measure for segmenting WM from GM.
RESUMEN. Presentamos la evolución y evaluación de una plataforma de e-learning denotada ACME. ACM... more RESUMEN. Presentamos la evolución y evaluación de una plataforma de e-learning denotada ACME. ACME es un entorno virtual de soporte a la docencia presencial que personaliza el aprendizaje del alumno a través de la asignación, ayuda y corrección automática de problemas. El ...
The majority of Computer Based Assessment (CBA) environments have been designed for fixed-respons... more The majority of Computer Based Assessment (CBA) environments have been designed for fixed-response questions. This feature is not enough for the university context since not all the skills can be reduced to this typology of questions and free response exercises are required. In this paper, we present a web-based tool designed to automatically correct exercises that require a diagram or a graph to be solved. The main novelty of this tool is the strategy used for the correction. The tool starts without the knowledge about correct and incorrect solutions and then learns about the solutions provided by teachers and students. It automatically records the information of all entered solutions, the teacher correction and the corresponding feedback in a system database. When a new student solution is entered the information of the database is used for correction. The main components of the tool are the graph editor module, designed to support diagram drawing, and the correction module, which corrects the solutions entered by the students. These modules are integrated in a more general e-learning platform denoted ACME. ACME provides teachers all functionalities required for student work tracking, assessment, personalized attention, etc. The proposed tool has been evaluated on experimental group.
The paper presents a web-based tool designed to give support to teaching and learning of UML clas... more The paper presents a web-based tool designed to give support to teaching and learning of UML class diagrams. The proposed UML environment is capable to correct automatically UML class diagrams exercises providing feedback to the student immediately. The tool is part of a more general framework, denoted ACME, which provides the main functionalities of an e-learning platform. The tool has been used in a first experimental group of an introductory database course.
International Journal of Emerging Technologies in Learning, 2010
... A Formative Assessment Tool for Conceptual Database Design Using UML Class Diagram. Josep Sol... more ... A Formative Assessment Tool for Conceptual Database Design Using UML Class Diagram. Josep Soler, Imma Boada, Ferran Prados, Jordi Poch, Ramon Fabregat. Abstract. Database design is one of the main topics of any introductory database course. ...
This paper presents new algorithms to compute ambient occlusion for volumetric data. Ambient occl... more This paper presents new algorithms to compute ambient occlusion for volumetric data. Ambient occlusion is used in video-games and film animation to mimic the indirect lighting of global illumination. We extend a novel interpretation of ambient occlusion to volumetric models that measures how big portion of the tangent sphere of a surface belongs to the set of occluded points, and propose statistically robust estimates for the ambient occlusion value. The data needed by this estimate can be obtained by separable filtering of the voxel array. As ambient occlusion is meant to obtain global illumination effects, it can provide decisive clues in interpreting the data. The new algorithms obtain smooth shading and can be computed at interactive rates, being thus appropriate for dynamic models exploration.
ABSTRACT Different quality metrics have been proposed in the literature to evaluate how well a vi... more ABSTRACT Different quality metrics have been proposed in the literature to evaluate how well a visualization represents the underlying data. In this paper, we present a new information-theoretic framework that quantifies the information transfer between the source data set and the rendered image. This approach is based on the definition of an observation channel whose input and output are given by the intensity values of the volumetric data set and the pixel colors, respectively. From this channel, the mutual information, a measure of information transfer or correlation between the input and the output, is used as a metric to evaluate the visualization quality. The usefulness of the proposed observation channel is illustrated with three fundamental visualization applications: selection of informative viewpoints, transfer function design, and light positioning.
To evaluate diffusion anisotropy from diffusion tensor imaging using new measures derived from He... more To evaluate diffusion anisotropy from diffusion tensor imaging using new measures derived from Hellinger divergences and from compositional data distances. New anisotropy measures obtained from the diffusion tensor imaging were measured and compared with classic ones such as fractional anisotropy (FA) and relative anisotropy (RA). The evaluation was done using the three-phase plot (3P-plot). The measures were compared with regard to their sensitivity to detect white and gray matter changes on human DTI data acquired from five normal volunteers. For each volunteer, different volumes of interest located in white matter (WM) and gray matter (GM) were considered. The proposed Compositional Kullback-Leibler (KLA) and the classic FA had a similar behavior, although KLA detected better the transitions between white and gray matter. Moreover, KLA showed a better discrimination in areas with great confluence of fibers. KLA detects better than FA the difference between WM and GM. This leads KLA to be a good measure for segmenting WM from GM.
RESUMEN. Presentamos la evolución y evaluación de una plataforma de e-learning denotada ACME. ACM... more RESUMEN. Presentamos la evolución y evaluación de una plataforma de e-learning denotada ACME. ACME es un entorno virtual de soporte a la docencia presencial que personaliza el aprendizaje del alumno a través de la asignación, ayuda y corrección automática de problemas. El ...
The majority of Computer Based Assessment (CBA) environments have been designed for fixed-respons... more The majority of Computer Based Assessment (CBA) environments have been designed for fixed-response questions. This feature is not enough for the university context since not all the skills can be reduced to this typology of questions and free response exercises are required. In this paper, we present a web-based tool designed to automatically correct exercises that require a diagram or a graph to be solved. The main novelty of this tool is the strategy used for the correction. The tool starts without the knowledge about correct and incorrect solutions and then learns about the solutions provided by teachers and students. It automatically records the information of all entered solutions, the teacher correction and the corresponding feedback in a system database. When a new student solution is entered the information of the database is used for correction. The main components of the tool are the graph editor module, designed to support diagram drawing, and the correction module, which corrects the solutions entered by the students. These modules are integrated in a more general e-learning platform denoted ACME. ACME provides teachers all functionalities required for student work tracking, assessment, personalized attention, etc. The proposed tool has been evaluated on experimental group.
The paper presents a web-based tool designed to give support to teaching and learning of UML clas... more The paper presents a web-based tool designed to give support to teaching and learning of UML class diagrams. The proposed UML environment is capable to correct automatically UML class diagrams exercises providing feedback to the student immediately. The tool is part of a more general framework, denoted ACME, which provides the main functionalities of an e-learning platform. The tool has been used in a first experimental group of an introductory database course.
International Journal of Emerging Technologies in Learning, 2010
... A Formative Assessment Tool for Conceptual Database Design Using UML Class Diagram. Josep Sol... more ... A Formative Assessment Tool for Conceptual Database Design Using UML Class Diagram. Josep Soler, Imma Boada, Ferran Prados, Jordi Poch, Ramon Fabregat. Abstract. Database design is one of the main topics of any introductory database course. ...
This paper presents new algorithms to compute ambient occlusion for volumetric data. Ambient occl... more This paper presents new algorithms to compute ambient occlusion for volumetric data. Ambient occlusion is used in video-games and film animation to mimic the indirect lighting of global illumination. We extend a novel interpretation of ambient occlusion to volumetric models that measures how big portion of the tangent sphere of a surface belongs to the set of occluded points, and propose statistically robust estimates for the ambient occlusion value. The data needed by this estimate can be obtained by separable filtering of the voxel array. As ambient occlusion is meant to obtain global illumination effects, it can provide decisive clues in interpreting the data. The new algorithms obtain smooth shading and can be computed at interactive rates, being thus appropriate for dynamic models exploration.
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Papers by Imma Boada