Browsing by Author "Livesu, Marco"

Now showing 1 - 8 of 8
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    Computational Assemblies: Analysis, Design, and Fabrication
    (The Eurographics Association, 2022) Song, Peng; Wang, Ziqi; Livesu, Marco; Hahmann, Stefanie; Patow, Gustavo A.
    Assemblies are ubiquitous in our daily life, such as toys, electronic devices, furniture, and architecture. They enable to build large and complex objects by composing small yet simpler parts, facilitating fabrication, storage, maintenance, and usage. However, designing assemblies is a highly non-trivial task because one needs to consider not only the properties of each individual components, but also of the whole assembly, such as aesthetics and stability. Motivated by recent advancements in digital fabrication, various computational techniques have been developed to analyze, design, and fabricate assemblies, aiming to enable general users to easily personalize them. This tutorial will give an introduction to these computational techniques, focusing on four fundamental aspects, i.e., parts fabricability, parts joining, assembly planning, and structural stability. In this tutorial, we will take a deep dive into computational methods to analyze these aspects for a given assembly as well as to design and fabricate assemblies that satisfy user-specified requirements in these aspects. This tutorial assumes knowledge of the fundamentals of computer graphics. Attendees should come away from this tutorial with a broad understanding of current work in computational assemblies, as well as familiarity with the necessary knowledge to start their own research in this area.
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    Frontmatter: STAG 2018: Smart Tools and Applications in computer Graphics
    (The Eurographics Association, 2018) Signoroni, Alberto; Livesu, Marco; Agus, Marco; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
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    HexBox: Interactive Box Modeling of Hexahedral Meshes
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Zoccheddu, Francesco; Gobbetti, Enrico; Livesu, Marco; Pietroni, Nico; Cherchi, Gianmarco; Memari, Pooran; Solomon, Justin
    We introduce HexBox, an intuitive modeling method and interactive tool for creating and editing hexahedral meshes. Hexbox brings the major and widely validated surface modeling paradigm of surface box modeling into the world of hex meshing. The main idea is to allow the user to box-model a volumetric mesh by primarily modifying its surface through a set of topological and geometric operations. We support, in particular, local and global subdivision, various instantiations of extrusion, removal, and cloning of elements, the creation of non-conformal or conformal grids, as well as shape modifications through vertex positioning, including manual editing, automatic smoothing, or, eventually, projection on an externally-provided target surface. At the core of the efficient implementation of the method is the coherent maintenance, at all steps, of two parallel data structures: a hexahedral mesh representing the topology and geometry of the currently modeled shape, and a directed acyclic graph that connects operation nodes to the affected mesh hexahedra. Operations are realized by exploiting recent advancements in gridbased meshing, such as mixing of 3-refinement, 2-refinement, and face-refinement, and using templated topological bridges to enforce on-the-fly mesh conformity across pairs of adjacent elements. A direct manipulation user interface lets users control all operations. The effectiveness of our tool, released as open source to the community, is demonstrated by modeling several complex shapes hard to realize with competing tools and techniques.
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    A Mesh Generation Perspective on Robust Mappings
    (The Eurographics Association, 2020) Livesu, Marco; Biasotti, Silvia and Pintus, Ruggero and Berretti, Stefano
    Mapping a shape to some parametric domain is a fundamental tool in graphics and scientific computing. In practice, a map between two shapes is commonly represented by two meshes with same connectivity and different embedding. The standard approach is to input a mesh embedded in one domain plus a set of prescribed positions for its boundary vertices in the other domain, and compute the position of the interior points in the mesh. For the 2d case, there are numerous robust tools that follow this scheme. However, theoretical issues prevent them to scale to 3d domains, thus the robust generation of volumetric maps remains an important open scientific problem. Inspired by basic principles in mesh generation, in this paper we present the reader a novel point of view on mesh parameterization. We consider connectivity as an additional unknown, and assume that our inputs are just two boundaries that enclose the domains we want to connect. We compute the map by simultaneously growing the same mesh inside both shapes in an advancing front fashion. This change in perspective allows us to recast the parameterization problem as a mesh generation problem, granting access to a wide set of mature tools that are typically not used in this setting. Our practical outcome is a provably robust yet trivial to implement algorithm that maps non convex planar shapes to convex ones. Perhaps more interestingly, we speculate on possible extensions to planar maps between non convex domains, and to volumetric maps as well, listing the major challenges that arise. Differently from prior methods, our analysis leaves us reasonable hope that an extension to volumes is possible.
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    Practical Computation of the Cut Locus on Discrete Surfaces
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Mancinelli, Claudio; Livesu, Marco; Puppo, Enrico; Digne, Julie and Crane, Keenan
    We present a novel method to compute the cut locus of a distance function encoded on a polygonal mesh. Our method exploits theoretical findings about the cut locus and - with a combination of analytic, geometric and topological tools - it is able to compute a topologically correct and geometrically accurate approximation of it. Our result can be either restricted to the mesh edges, or aligned with the real cut locus. Both outputs may be useful for practical applications. We also provide a convenient tool to optionally prune the weak branches of the cut locus, simplifying its structure. Our approach supersedes prior art, in that it is easier to use and also orders of magnitude faster. In fact, it depends on just one parameter, and it flawlessly operates on meshes with high genus and very high element count at interactive rates. We experiment with different datasets and methods for geodesic distance estimation. We also present applications to local and global surface parameterization.
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    ProMED: Production Optimization for Additive Manufacturing of Medical Devices
    (The Eurographics Association, 2022) Attene, Marco; Berti, Tiziano; Cabiddu, Daniela; Garosi, Antonio; Livesu, Marco; Pasztor, Zsolt; Petrovszki, Daniel; Ranieri, Andrea; Cabiddu, Daniela; Schneider, Teseo; Allegra, Dario; Catalano, Chiara Eva; Cherchi, Gianmarco; Scateni, Riccardo
    In metal 3D printing, and in particular in the production of dental implants and prosthodontics, a careful geometric analysis of the parts is key to maximize the overall throughput and minimize fabrication costs. Herewith we describe the main results obtained within the European Project DIGITBrain/ProMED, whose objective is to optimize the production of customized metal medical devices. ProMED delivers a digital twin of an existing production pipeline and allows for the quick simulation of a large number of fabrication scenarios. This is achieved thanks to a clever geometric analysis driving the optimal orientation of the part in the platform combined with a geometry-based process simulator that makes it possible to estimate fabrication time, material consumption, human labour, and other useful information that greatly supports users in the task of optimizing the overall fabrication performances from many meaningful points of view. Compared to standard simulation software provided by printer vendors, our approach can be orders of magnitude faster: this makes it possible to analyze and compare a great number of scenarios to support companies in their day-by-day decisions for real productions.
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    Topological Initialization of Injective Integer Grid Maps
    (The Eurographics Association, 2022) Livesu, Marco; Cabiddu, Daniela; Schneider, Teseo; Allegra, Dario; Catalano, Chiara Eva; Cherchi, Gianmarco; Scateni, Riccardo
    Integer Grid Maps (IGM) are a class of mappings characterized by integer isolines that align up to unit translations and rotations of multiples of 90 degrees. They are widely used in the context of remeshing, to lay a quadrilateral grid onto the mapped surface. Computing an IGM is notoriously a challenging task, because it requires to solve a numerical problem with mixed discrete and continuous variables which is known to be NP-Hard. As a result, state of the art methods rely on heuristics that may occasionally fail to produce a valid quadrilateral mesh. Existing pipelines incorporate a final sanitization step which attempts to fix such defects, but no guaranteees can be given in this regard. In this paper we propose a simple topological construction that allows to reduce the problem of computing an IGM to the one of mapping a topological disk to a convex domain. This is a much easier problem to deal with, because it does not endow integer translational and rotational constraints, permitting to obtain a parameterization that is guaranteed to incorporate all the correct integer transitions and to not contain degenerate or inverted elements. Despite provably correct, the so generated maps contain a considerable amount of geometric distortion and a poor quad connectivity, making this technique more suitable for a robust initialization rather than for the computation of an application-ready IGM. In the article we present the details of our construction, also analyzing its geometric and topological properties.
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    VOLMAP: a Large Scale Benchmark for Volume Mappings to Simple Base Domains
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Cherchi, Gianmarco; Livesu, Marco; Memari, Pooran; Solomon, Justin
    Correspondences between geometric domains (mappings) are ubiquitous in computer graphics and engineering, both for a variety of downstream applications and as core building blocks for higher level algorithms. In particular, mapping a shape to a convex or star-shaped domain with simple geometry is a fundamental module in existing pipelines for mesh generation, solid texturing, generation of shape correspondences, advanced manufacturing etc. For the case of surfaces, computing such a mapping with guarantees of injectivity is a solved problem. Conversely, robust algorithms for the generation of injective volume mappings to simple polytopes are yet to be found, making this a fundamental open problem in volume mesh processing. VOLMAP is a large scale benchmark aimed to support ongoing research in volume mapping algorithms. The dataset contains 4.7K tetrahedral meshes, whose boundary vertices are mapped to a variety of simple domains, either convex or star-shaped. This data constitutes the input for candidate algorithms, which are then required to position interior vertices in the domain to obtain a volume map. Overall, this yields more than 22K alternative test cases. VOLMAP also comprises tools to process this data, analyze the resulting maps, and extend the dataset with new meshes, boundary maps and base domains. This article provides a brief overview of the field, discussing its importance and the lack of effective techniques. We then introduce both the dataset and its major features. An example of comparative analysis between two existing methods is also present.