ORCID Profile
0000-0002-8271-2102
Current Organisations
University of Technology Sydney Faculty of Engineering and Information Technology
,
University of Technology Sydney
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Publisher: The Eurographics Association
Date: 2014
DOI: 10.2312/GCH.20141306
Publisher: Springer Science and Business Media LLC
Date: 12-08-2020
Publisher: Wiley
Date: 04-03-2013
DOI: 10.1111/CGF.12014
Publisher: IOP Publishing
Date: 15-09-2023
Abstract: Spheroids are microtissues containing cells organized in a spherical shape whose diameter is usually less than a millimetre. Depending on the properties of the environment they are placed in, some nearby spheroids spontaneously fuse and generate a tissue. Given their potential to mimic features typical of body parts and their ability to assemble by fusing in permissive hydrogels, they have been used as building blocks to 3D bioprint human tissue parts. Parameters controlling the shape and size of a bioprinted tissue using fusing spheroid cultures include cell composition, hydrogel properties, and their relative initial position. Hence, simulating, anticipating, and then controlling the spheroid fusion process is essential to control the shape and size of the bioprinted tissue.& #xD & #xD This study presents the first physically-based framework to simulate the fusion process of bioprinted spheroids. The simulation is based on elastic-plastic solid and fluid continuum mechanics models. Both models use the “smoothed particle hydrodynamics” (SPH) method, which is based on discretizing the continuous medium into a finite number of particles and solving the differential equations related to the physical properties (e.g., Navier-Stokes equation) using a smoothing kernel function.& #xD & #xD To further investigate the effects of such parameters on spheroid shape and geometry, we performed sensitivity and morphological analysis to validate our simulations with in-vitro spheroids. Through our in-silico simulations by changing the aforementioned parameters, we show that the proposed models appropriately simulate the range of the elastic-plastic behaviours of in-vitro fusing spheroids to generate tissues of desired shapes and sizes.& #xD & #xD Altogether, this study presented a physically-based simulation that can provide a framework for monitoring and controlling the geometrical shape of spheroids, directly impacting future research using spheroids for tissue bioprinting.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2020
Publisher: Association for Computing Machinery (ACM)
Date: 27-07-2014
Abstract: We present a robust method for computing locally bijective global parametrizations aligned with a given cross-field. The singularities of the parametrization in general agree with singularities of the field, except in a small number of cases when several additional cones need to be added in a controlled way. Parametric lines can be constrained to follow an arbitrary set of feature lines on the surface. Our method is based on constructing an initial quad patch partition using robust cross-field integral line tracing. This process is followed by an algorithm modifying the quad layout structure to ensure that consistent parametric lengths can be assigned to the edges. For most meshes, the layout modification algorithm does not add new singularities a small number of singularities may be added to resolve an explicitly described set of layouts. We demonstrate that our algorithm succeeds on a test data set of over a hundred meshes.
Publisher: The Eurographics Association
Date: 2010
DOI: 10.2312/LOCALCHAPTEREVENTS/ITALCHAP/ITALIANCHAPCONF2010/095-102
Publisher: Elsevier BV
Date: 06-2023
Publisher: Association for Computing Machinery (ACM)
Date: 20-11-2017
Abstract: We propose a novel framework for the computational design of tensegrity structures, which are constructions made of struts and cables, held rigid by continuous tension between the elements. Tensegrities are known to be difficult to design---existing design methods are often restricted to using symmetric or templated configurations, limiting the design space to simple constructions. We introduce an algorithm to automatically create free-form stable tensegrity designs that satisfy both fabrication and geometric constraints, and faithfully approximate input geometric shapes. Our approach sidesteps the usual force-based approach in favor of a geometric optimization on the positions of the elements. Equipped with this formulation, we provide a design framework to explore the highly constrained space of tensegrity structures. We validate our method with simulations and real-world constructions.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Wiley
Date: 05-2010
Publisher: Inderscience Publishers
Date: 2011
Publisher: Wiley
Date: 05-2021
DOI: 10.1111/CGF.142625
Abstract: We introduce a novel geometry‐processing pipeline to guide the fabrication of complex shapes from a single block of material using 4‐axis CNC milling machines. This setup extends classical 3‐axis CNC machining with an extra degree of freedom to rotate the object around a fixed axis. The first step of our pipeline identifies the rotation axis that maximizes the overall fabrication accuracy. Then we identify two height‐field regions at the rotation axis's extremes used to secure the block on the rotation tool. We segment the remaining portion of the mesh into a set of height‐fields whose principal directions are orthogonal to the rotation axis. The segmentation balances the approximation quality, the boundary smoothness, and the total number of patches. Additionally, the segmentation process takes into account the object's geometric features, as well as saliency information. The output is a set of meshes ready to be processed by off‐the‐shelf software for the 3‐axis tool‐path generation. We present several results to demonstrate the quality and efficiency of our approach to a range of inputs.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2011
Publisher: IEEE
Date: 10-2013
Publisher: Association for Computing Machinery (ACM)
Date: 2014
DOI: 10.1145/2537852
Abstract: Mesh joinery is an innovative method to produce illustrative shape approximations suitable for fabrication. Mesh joinery is capable of producing complex fabricable structures in an efficient and visually pleasing manner. We represent an input geometry as a set of planar pieces arranged to compose a rigid structure, by exploiting an efficient slit mechanism. Since slices are planar, to fabricate them a standard 2D cutting system is enough. We automatically arrange slices according to a smooth cross-field defined over the surface. Cross-fields allow representing global features that characterize the appearance of the shape. Slice placement conforms to specific manufacturing constraints.
Publisher: The Eurographics Association
Date: 2014
DOI: 10.2312/GCH.20141312
Publisher: Association for Computing Machinery (ACM)
Date: 04-12-2018
Abstract: We propose FlexMaps, a novel framework for fabricating smooth shapes out of flat, flexible panels with tailored mechanical properties. We start by mapping the 3D surface onto a 2D domain as in traditional UV mapping to design a set of deformable flat panels called FlexMaps. For these panels, we design and obtain specific mechanical properties such that, once they are assembled, the static equilibrium configuration matches the desired 3D shape. FlexMaps can be fabricated from an almost rigid material, such as wood or plastic, and are made flexible in a controlled way by using computationally designed spiraling microstructures.
Publisher: Association for Computing Machinery (ACM)
Date: 18-10-2022
DOI: 10.1145/3554920
Abstract: In this article, we provide a detailed survey of techniques for hexahedral mesh generation. We cover the whole spectrum of alternative approaches to mesh generation, as well as post-processing algorithms for connectivity editing and mesh optimization. For each technique, we highlight capabilities and limitations, also pointing out the associated unsolved challenges. Recent relaxed approaches, aiming to generate not pure-hex but hex-dominant meshes, are also discussed. The required background, pertaining to geometrical as well as combinatorial aspects, is introduced along the way.
Publisher: International Information and Engineering Technology Association
Date: 06-2017
Publisher: Elsevier BV
Date: 05-2005
Publisher: Springer Science and Business Media LLC
Date: 21-04-2010
Publisher: Wiley
Date: 10-2008
Publisher: IEEE
Date: 08-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2010
DOI: 10.1109/MCG.2009.153
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2010
DOI: 10.1109/TVCG.2009.96
Publisher: Association for Computing Machinery (ACM)
Date: 09-06-2020
DOI: 10.1145/3375677
Abstract: We introduce an efficient method for designing shell reinforcements of minimal weight. Inspired by classical Michell trusses, we create a reinforcement layout whose members are aligned with optimal stress directions, then optimize their shape minimizing the volume while keeping stresses bounded. We exploit two predominant techniques for reinforcing shells: adding ribs aligned with stress directions and using thicker walls on regions of high stress. Most previous work can generate either only ribs or only variable-thickness walls. However, in the general case, neither approach by itself will provide optimal solutions. By using a more precise volume model, our method is capable of producing optimized structures with the full range of qualitative behaviors: from ribs to walls and smoothly transitioning in between. Our method includes new algorithms for determining the layout of reinforcement structure elements, and an efficient algorithm to optimize their shape, minimizing a non-linear non-convex functional at a fraction of the cost and with better optimality compared to standard solvers. We demonstrate the optimization results for a variety of shapes and the improvements it yields in the strength of 3D-printed objects.
Publisher: Association for Computing Machinery (ACM)
Date: 27-07-2015
DOI: 10.1145/2766937
Abstract: We introduce elastic textures: a set of parametric, tileable, printable, cubic patterns achieving a broad range of isotropic elastic material properties: the softest pattern is over a thousand times softer than the stiffest, and the Poisson's ratios range from below zero to nearly 0.5. Using a combinatorial search over topologies followed by shape optimization, we explore a wide space of truss-like, symmetric 3D patterns to obtain a small family. This pattern family can be printed without internal support structure on a single-material 3D printer and can be used to fabricate objects with prescribed mechanical behavior. The family can be extended easily to create anisotropic patterns with target orthotropic properties. We demonstrate that our elastic textures are able to achieve a user-supplied varying material property distribution. We also present a material optimization algorithm to choose material properties at each point within an object to best fit a target deformation under a prescribed scenario. We show that, by fabricating these spatially varying materials with elastic textures, the desired behavior is achieved.
Publisher: The Eurographics Association
Date: 2007
DOI: 10.2312/LOCALCHAPTEREVENTS/ITALCHAP/ITALIANCHAPCONF2007/155-160
Publisher: Wiley
Date: 21-02-2018
DOI: 10.1111/CGF.13327
Publisher: Wiley
Date: 09-07-2019
DOI: 10.1111/CGF.13801
Publisher: Association for Computing Machinery (ACM)
Date: 12-2011
Abstract: We present a method for the global parametrization of meshes that preserves alignment to a cross field in input while obtaining a parametric domain made of few coarse axis-aligned rectangular patches, which form an abstract base complex without T-junctions. The method is based on the topological simplification of the cross field in input, followed by global smoothing.
Publisher: Wiley
Date: 08-2023
DOI: 10.1111/CGF.14899
Abstract: 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 sub ision, 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 grid‐based 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.
Publisher: Association for Computing Machinery (ACM)
Date: 30-07-2018
Abstract: We propose a new method for fabricating digital objects through reusable silicone molds. Molds are generated by casting liquid silicone into custom 3D printed containers called metamolds. Metamolds automatically define the cuts that are needed to extract the cast object from the silicone mold. The shape of metamolds is designed through a novel segmentation technique, which takes into account both geometric and topological constraints involved in the process of mold casting. Our technique is simple, does not require changing the shape or topology of the input objects, and only requires of-the-shelf materials and technologies. We successfully tested our method on a set of challenging ex les with complex shapes and rich geometric detail.
Publisher: Association for Computing Machinery (ACM)
Date: 12-08-2020
Abstract: We present a new fully automatic block-decomposition algorithm for feature-preserving, strongly hex-dominant meshing, that yields results with a drastically larger percentage of hex elements than prior art. Our method is guided by a surface field that conforms to both surface curvature and feature lines, and exploits an ordered set of cutting loops that evenly cover the input surface, defining an arrangement of loops suitable for hex-element generation. We decompose the solid into coarse blocks by iteratively cutting it with surfaces bounded by these loops. The vast majority of the obtained blocks can be turned into hexahedral cells via simple midpoint sub ision. Our method produces pure hexahedral meshes in approximately 80% of the cases, and hex-dominant meshes with less than 2% non-hexahedral cells in the remaining cases. We demonstrate the robustness of our method on 70+ models, including CAD objects with features of various complexity, organic and synthetic shapes, and provide extensive comparisons to prior art, demonstrating its superiority.
Publisher: Wiley
Date: 10-2016
DOI: 10.1111/CGF.13045
Publisher: Wiley
Date: 22-08-2022
DOI: 10.1111/CGF.14581
Abstract: Moulding refers to a set of manufacturing techniques in which a mould, usually a cavity or a solid frame, is used to shape a liquid or pliable material into an object of the desired shape. The popularity of moulding comes from its effectiveness, scalability and versatility in terms of employed materials. Its relevance as a fabrication process is demonstrated by the extensive literature covering different aspects related to mould design, from material flow simulation to the automation of mould geometry design. In this state‐of‐the‐art report, we provide an extensive review of the automatic methods for the design of moulds, focusing on contributions from a geometric perspective. We classify existing mould design methods based on their computational approach and the nature of their target moulding process. We summarize the relationships between computational approaches and moulding techniques, highlighting their strengths and limitations. Finally, we discuss potential future research directions.
Publisher: Challenging Glass Conference Proceedings
Date: 2020
DOI: 10.7480/CGC.7.4496
Publisher: Elsevier BV
Date: 05-2019
Publisher: The Eurographics Association
Date: 2016
DOI: 10.2312/GDF.20161073
Publisher: Wiley
Date: 09-2007
Publisher: Elsevier BV
Date: 08-2020
Publisher: ACM
Date: 05-11-2007
Publisher: Association for Computing Machinery (ACM)
Date: 11-11-2016
Abstract: We present FlexMolds, a novel computational approach to automatically design flexible, reusable molds that, once 3D printed, allow us to physically fabricate, by means of liquid casting, multiple copies of complex shapes with rich surface details and complex topology. The approach to design such flexible molds is based on a greedy bottom-up search of possible cuts over an object, evaluating for each possible cut the feasibility of the resulting mold. We use a dynamic simulation approach to evaluate candidate molds, providing a heuristic to generate forces that are able to open, detach, and remove a complex mold from the object it surrounds. We have tested the approach with a number of objects with nontrivial shapes and topologies.
Publisher: Association for Computing Machinery (ACM)
Date: 12-2011
Abstract: We present a method to globally parameterize a surface represented by height maps over a set of planes (range images). In contrast to other parametrization techniques, we do not start with a manifold mesh. The parametrization we compute defines a manifold structure, it is seamless and globally smooth, can be aligned to geometric features and shows good quality in terms of angle and area preservation, comparable to current parametrization techniques for meshes. Computing such global seamless parametrization makes it possible to perform quad remeshing, texture mapping and texture synthesis and many other types of geometry processing operations. Our approach is based on a formulation of the Poisson equation on a manifold structure defined for the surface by the range images. Construction of such global parametrization requires only a way to project surface data onto a set of planes, and can be applied directly to implicit surfaces, nonmanifold surfaces, very large meshes, and collections of range scans. We demonstrate application of our technique to all these geometry types.
Publisher: ACM
Date: 10-07-2023
Publisher: Association for Computing Machinery (ACM)
Date: 27-07-2015
DOI: 10.1145/2766964
Abstract: We propose an interactive quadrangulation method based on a large collection of patterns that are learned from models manually designed by artists. The patterns are distilled into compact quadrangulation rules and stored in a database. At run-time, the user draws strokes to define patches and desired edge flows, and the system queries the database to extract fitting patterns to tessellate the sketches' interiors. The quadrangulation patterns are general and can be applied to tessellate large regions while controlling the positions of the singularities and the edge flow. We demonstrate the effectiveness of our algorithm through a series of live retopology sessions and an informal user study with three professional artists.
Publisher: Elsevier BV
Date: 06-2016
Publisher: The Eurographics Association
Date: 2016
Publisher: Wiley
Date: 18-11-2015
DOI: 10.1111/CGF.12781
Publisher: ACM
Date: 17-11-2019
Publisher: Association for Computing Machinery (ACM)
Date: 12-07-2019
Abstract: We propose a novel technique for the automatic design of molds to cast highly complex shapes. The technique generates composite, two-piece molds. Each mold piece is made up of a hard plastic shell and a flexible silicone part. Thanks to the thin, soft, and smartly shaped silicone part, which is kept in place by a hard plastic shell, we can cast objects of unprecedented complexity. An innovative algorithm based on a volumetric analysis defines the layout of the internal cuts in the silicone mold part. Our approach can robustly handle thin protruding features and intertwined topologies that have caused previous methods to fail. We compare our results with state of the art techniques, and we demonstrate the casting of shapes with extremely complex geometry.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2011
DOI: 10.1109/TVCG.2011.28
Publisher: Springer Nature Switzerland
Date: 31-10-2023
Publisher: Elsevier BV
Date: 08-2023
Publisher: Springer Science and Business Media LLC
Date: 18-03-2008
Publisher: Association for Computing Machinery (ACM)
Date: 26-07-2010
Abstract: High-order and regularly s led surface representations are more efficient and compact than general meshes and considerably simplify many geometric modeling and processing algorithms. A number of recent algorithms for conversion of arbitrary meshes to regularly s led form (typically quadrangulation) aim to align the resulting mesh with feature lines of the geometry. While resulting in a substantial improvement in mesh quality, feature alignment makes it difficult to obtain coarse regular patch partitions of the mesh. In this paper, we propose an approach to constructing patch layouts consisting of small numbers of quadrilateral patches while maintaining good feature alignment. To achieve this, we use quadrilateral T-meshes, for which the intersection of two faces may not be the whole edge or vertex, but a part of an edge. T-meshes offer more flexibility for reduction of the number of patches and vertices in a base domain while maintaining alignment with geometric features. At the same time, T-meshes retain many desirable features of quadrangulations, allowing construction of high-order representations, easy packing of regularly s led geometric data into textures, as well as supporting different types of discretizations for physical simulation.
Publisher: Springer International Publishing
Date: 2015
Location: Italy
Location: Australia
No related grants have been discovered for NICO PIETRONI.