Browsing by Author "Tarini, Marco"

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    At‐Most‐Hexa Meshes
    (© 2022 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2022) Bukenberger, Dennis R.; Tarini, Marco; Lensch, Hendrik P. A.; Hauser, Helwig and Alliez, Pierre
    Volumetric polyhedral meshes are required in many applications, especially for solving partial differential equations on finite element simulations. Still, their construction bears several additional challenges compared to boundary‐based representations. Tetrahedral meshes and (pure) hex‐meshes are two popular formats in scenarios like CAD applications, offering opposite advantages and disadvantages. Hex‐meshes are more intricate to construct due to the global structure of the meshing, but feature much better regularity, alignment, are more expressive, and offer the same simulation accuracy with fewer elements. Hex‐dominant meshes, where most but not all cell elements have a hexahedral structure, constitute an attractive compromise, potentially unlocking benefits from both structures, but their generality makes their employment in downstream applications difficult. In this work, we introduce a strict subset of general hex‐dominant meshes, which we term ‘at‐most‐hexa meshes’, in which most cells are still hexahedral, but no cell has more than six boundary faces, and no face has more than four sides. We exemplify the ease of construction of at‐most‐hexa meshes by proposing a frugal and straightforward method to generate high‐quality meshes of this kind, starting directly from hulls or point clouds, for example, from a 3D scan. In contrast to existing methods for (pure) hexahedral meshing, ours does not require an intermediate parameterization of other costly pre‐computations and can start directly from surfaces or samples. We leverage a Lloyd relaxation process to exploit the synergistic effects of aligning an orientation field in a modified 3D Voronoi diagram using the norm for cubical cells. The extracted geometry incorporates regularity as well as feature alignment, following sharp edges and curved boundary surfaces. We introduce specialized operations on the three‐dimensional graph structure to enforce consistency during the relaxation. The resulting algorithm allows for an efficient evaluation with parallel algorithms on GPU hardware and completes even large reconstructions within minutes.
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    CMH: Coordinates Manifold Harmonics for Functional Remeshing
    (The Eurographics Association, 2019) Marin, Riccardo; Melzi, Simone; Musoni, Pietro; Bardon, Filippo; Tarini, Marco; Castellani, Umberto; Biasotti, Silvia and Lavoué, Guillaume and Veltkamp, Remco
    In digital world reconstruction, 2-dimensional surface of real objects are often obtained as polygonal meshes after an acquisition procedure using 3D sensors. However, such representation requires several manual efforts from highly experts to correct the irregularity of tessellation and make it suitable for professional applications, such as those in the gaming or movie industry. Moreover, for modelling and animation purposes it is often required that the same connectivity is shared among two or more different shapes. In this paper we propose a new method that exploits a remeshing-by-matching approach where the observed noisy shape inherits a regular tessellation from a target shape which already satisfies the professional constraints. A fully automatic pipeline is introduced based on a variation of the functional mapping framework. In particular, a new set of basis functions, namely the Coordinates Manifold Harmonics (CMH), is properly designed for this tessellation transfer task. In our experiments an exhaustive quantitative and quality evaluation is reported for human body shapes in T-pose where the effectiveness of the proposed functional remeshing is clearly shown in comparison with other methods.
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    EUROGRAPHICS 2019: Education Papers Frontmatter
    (Eurographics Association, 2019) Tarini, Marco; Galin, Eric; Tarini, Marco and Galin, Eric
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    Rethinking Texture Mapping
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Yuksel, Cem; Lefebvre, Sylvain; Tarini, Marco; Giachetti, Andrea and Rushmeyer, Holly
    The intrinsic problems of texture mapping, regarding its difficulties in content creation and the visual artifacts it causes in rendering, are well-known, but often considered unavoidable. In this state of the art report, we discuss various radically different ways to rethink texture mapping that have been proposed over the decades, each offering different advantages and trade-offs. We provide a brief description of each alternative texturing method along with an evaluation of its strengths and weaknesses in terms of applicability, usability, filtering quality, performance, and potential implementation related challenges.
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    Seamless Compressed Textures
    (The Eurographics Association, 2022) Maggiordomo, Andrea; Tarini, Marco; Sauvage, Basile; Hasic-Telalovic, Jasminka
    We present an algorithm to hide discontinuity artifacts at seams in GPU compressed textures. Texture mapping requires UV-maps, and UV-maps (in general) require texture seams; texture seams (in general) cause small visual artifacts in rendering; these can be prevented by careful, slight modifications a few texels around the seam. Unfortunately, GPU-based texture compression schemes are lossy and introduce their own slight modifications of texture values, nullifying that effort. The result is that texture compression may reintroduce the visual artefacts at seams. We modify a standard texture compression algorithm to make it aware of texture seams, resulting in compressed textures that still prevent the seam artefacts.
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    Texture Defragmentation for Photo-Reconstructed 3D Models
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Maggiordomo, Andrea; Cignoni, Paolo; Tarini, Marco; Mitra, Niloy and Viola, Ivan
    We propose a method to improve an existing parametrization (UV-map layout) of a textured 3D model, targeted explicitly at alleviating typical defects afflicting models generated with automatic photo-reconstruction tools from real-world objects. This class of 3D data is becoming increasingly important thanks to the growing popularity of reliable, ready-to-use photogrammetry software packages. The resulting textured models are richly detailed, but their underlying parametrization typically falls short of many practical requirements, particularly exhibiting excessive fragmentation and consequent problems. Producing a completely new UV-map, with standard parametrization techniques, and then resampling a new texture image, is often neither practical nor desirable for at least two reasons: first, these models have characteristics (such as inconsistencies, high resolution) that make them unfit for automatic or manual parametrization; second, the required resampling leads to unnecessary signal degradation because this process is unaware of the original texel densities. In contrast, our method improves the existing UV-map instead of replacing it, balancing the reduction of the map fragmentation with signal degradation due to resampling, while also avoiding oversampling of the original signal. The proposed approach is fully automatic and extensively tested on a large benchmark of photo-reconstructed models; quantitative evaluation evidences a drastic and consistent improvement of the mappings.
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    User-assisted Sphere-mesh Construction
    (The Eurographics Association, 2023) Paolillo, Davide; Taroni, Andrea; Tarini, Marco; Banterle, Francesco; Caggianese, Giuseppe; Capece, Nicola; Erra, Ugo; Lupinetti, Katia; Manfredi, Gilda
    In this study, we investigate the semi-automated generation of sphere-meshes as high-quality approximations for given threedimensional shapes, originally represented as common triangular meshes. A sphere-mesh is a class of geometric proxy defined as the volume swept by spheres with linearly interpolated centers and radii, that potentially strikes a good balance between conciseness of representation, simplicity of spatial queries, and expressive power, and is amenable to animations. Despite these favorable characteristics, its broader adoption in applications such as video games, physical simulation, or robotics is hindered by the difficulty of its construction, which remains an open problem. Existing fully automatic algorithms, based on interactive coarsening of the input mesh, fail to consistently produce satisfactory results, especially when very coarse sphere-meshes are sought. We improve on this situation with a 3D interface specifically designed to permit users to easily and intuitively modify the automatically generated models. The two phases (existing automatic algorithm and novel interactive tool), used in cascade, constitute a viable semi-automatic way to produce sphere-meshes. We test our method on several inputs tri-meshes, assess their quality, and finally experiment with a few downstream applications to exemplify the usability of our results.
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    Velocity Skinning for Real-time Stylized Skeletal Animation
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Rohmer, Damien; Tarini, Marco; Kalyanasundaram, Niranjan; Moshfeghifar, Faezeh; Cani, Marie-Paule; Zordan, Victor; Mitra, Niloy and Viola, Ivan
    Secondary animation effects are essential for liveliness. We propose a simple, real-time solution for adding them on top of standard skinning, enabling artist-driven stylization of skeletal motion. Our method takes a standard skeleton animation as input, along with a skin mesh and rig weights. It then derives per-vertex deformations from the different linear and angular velocities along the skeletal hierarchy. We highlight two specific applications of this general framework, namely the cartoonlike ''squashy'' and ''floppy'' effects, achieved from specific combinations of velocity terms. As our results show, combining these effects enables to mimic, enhance and stylize physical-looking behaviours within a standard animation pipeline, for arbitrary skinned characters. Interactive on CPU, our method allows for GPU implementation, yielding real-time performances even on large meshes. Animator control is supported through a simple interface toolkit, enabling to refine the desired type and magnitude of deformation at relevant vertices by simply painting weights. The resulting rigged character automatically responds to new skeletal animation, without further input.