Browsing by Author "Hahmann, Stefanie"

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    3D Design Of Ancient Garments
    (The Eurographics Association, 2019) Carrière, Melanie; Skouras, Melina; Hahmann, Stefanie; Rizvic, Selma and Rodriguez Echavarria, Karina
    3D Modeling of this kind of draped clothes worn by a virtual human body is a particularly challenging task in computer graphics primarily due to the combined difficulty of creating layers of numerous fine folds and draping a person with a procedure quite different from dressing modern clothes. We propose a procedural approach for synthesizing a toga draped around a virtual body by starting from a flat fabric. We recreate visible and invisible folds as well as layers of the garment. This approach is composed into different stages inspired by movements made by roman people as they put on their toga. To adjust the toga to the morphology of the 3D model, we present a technique to create the mesh of the toga that adapts to certain parameters of the human body. Using a physical-based simulator allows us to reach our final goal: A 3D model wearing a realistic toga.
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    Approximate Reconstruction of 3D Scenes From Bas-Reliefs
    (The Eurographics Association, 2019) Casati, Pierre; Ronfard, Rémi; Hahmann, Stefanie; Rizvic, Selma and Rodriguez Echavarria, Karina
    For thousands of years, bas-reliefs have been used to depict scenes of everyday life, mythology and historic events. Yet, the precise geometry of those scenes remains difficult to interpret and reconstruct. Over the past decade, methods have been developed for generating bas-reliefs from 3D scenes. In this paper, we investigate the inverse problem of interpreting and reconstructing 3D scenes from their bas-relief depictions. Even approximate reconstructions can be useful for art historians and museum exhibit designers, as a first entry to the complete interpretation of the narratives told in stone or marble. To create such approximate reconstructions, we present methods for extracting 3D base mesh models of all characters depicted in a bas-relief. We take advantages of the bas-relief geometry and high-level knowledge of human body proportions to recover body parts and their three-dimensional structure, even in severe cases of contact and occlusion. We present experimental results for 6 bas-relief depictions of Greek mythological and historical scenes involving 18 characters and draw conclusions for future work.
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    EUROGRAPHICS 2022: Tutorials Frontmatter
    (The Eurographics Association, 2022) Hahmann, Stefanie; Patow, Gustavo A.; Hahmann, Stefanie; Patow, Gustavo A.
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    Fashion Transfer: Dressing 3D Characters from Stylized Fashion Sketches
    (© 2021 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2021) Fondevilla, Amelie; Rohmer, Damien; Hahmann, Stefanie; Bousseau, Adrien; Cani, Marie‐Paule; Benes, Bedrich and Hauser, Helwig
    Fashion design often starts with hand‐drawn, expressive sketches that communicate the essence of a garment over idealized human bodies. We propose an approach to automatically dress virtual characters from such input, previously complemented with user‐annotations. In contrast to prior work requiring users to draw garments with accurate proportions over each virtual character to be dressed, our method follows a style transfer strategy : the information extracted from a single, annotated fashion sketch can be used to inform the synthesis of one to many new garment(s) with similar style, yet different proportions. In particular, we define the style of a loose garment from its silhouette and folds, which we extract from the drawing. Key to our method is our strategy to extract both shape and repetitive patterns of folds from the 2D input. As our results show, each input sketch can be used to dress a variety of characters of different morphologies, from virtual humans to cartoon‐style characters.
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    Geometric Construction of Auxetic Metamaterials
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Bonneau, Georges-Pierre; Hahmann, Stefanie; Marku, Johana; Mitra, Niloy and Viola, Ivan
    This paper is devoted to a category of metamaterials called auxetics, identified by their negative Poisson's ratio. Our work consists in exploring geometrical strategies to generate irregular auxetic structures. More precisely we seek to reduce the Poisson's ratio n, by pruning an irregular network based solely on geometric criteria. We introduce a strategy combining a pure geometric pruning algorithm followed by a physics-based testing phase to determine the resulting Poisson's ratio of our structures. We propose an algorithm that generates sets of irregular auxetic networks. Our contributions include geometrical characterization of auxetic networks, development of a pruning strategy, generation of auxetic networks with low Poisson's ratio, as well as validation of our approach.We provide statistical validation of our approach on large sets of irregular networks, and we additionally laser-cut auxetic networks in sheets of rubber. The findings reported here show that it is possible to reduce the Poisson's ratio by geometric pruning, and that we can generate irregular auxetic networks at lower processing times than a physics-based approach.