67 research outputs found
Cyclic animation using Partial differential Equations
YesThis work presents an efficient and fast method for achieving cyclic animation using Partial Differential Equations (PDEs). The boundary-value nature associ- ated with elliptic PDEs offers a fast analytic solution technique for setting up a framework for this type of animation. The surface of a given character is thus cre- ated from a set of pre-determined curves, which are used as boundary conditions so that a number of PDEs can be solved. Two different approaches to cyclic ani- mation are presented here. The first consists of using attaching the set of curves to a skeletal system hold- ing the animation for cyclic motions linked to a set mathematical expressions, the second one exploits the spine associated with the analytic solution of the PDE as a driving mechanism to achieve cyclic animation, which is also manipulated mathematically. The first of these approaches is implemented within a framework related to cyclic motions inherent to human-like char- acters, whereas the spine-based approach is focused on modelling the undulatory movement observed in fish when swimming. The proposed method is fast and ac- curate. Additionally, the animation can be either used in the PDE-based surface representation of the model or transferred to the original mesh model by means of
a point to point map. Thus, the user is offered with the choice of using either of these two animation repre- sentations of the same object, the selection depends on the computing resources such as storage and memory capacity associated with each particular application
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Modelling and Animation using Partial Differential Equations. Geometric modelling and computer animation of virtual characters using elliptic partial differential equations.
This work addresses various applications pertaining to the design, modelling and animation of parametric surfaces using elliptic Partial Differential Equations (PDE) which are produced via the PDE method. Compared with traditional surface generation techniques, the PDE method is an effective technique that can represent complex three-dimensional (3D) geometries in terms of a relatively small set of parameters. A PDE-based surface can be produced from a set of pre-configured curves that are used as the boundary conditions to solve a number of PDE. An important advantage of using this method is that most of the information required to define a surface is contained at its boundary. Thus, complex surfaces can be computed using only a small set of design parameters.
In order to exploit the advantages of this methodology various applications were developed that vary from the interactive design of aircraft configurations to the animation of facial expressions in a computer-human interaction system that utilizes an artificial intelligence (AI) bot for real time conversation. Additional applications of generating cyclic motions for PDE based human character integrated in a Computer-Aided Design (CAD) package as well as developing techniques to describe a given mesh geometry by a set of boundary conditions, required to evaluate the PDE method, are presented. Each methodology presents a novel approach for interacting with parametric surfaces obtained by the PDE method. This is due to the several advantages this surface generation technique has to offer. Additionally, each application developed in this thesis focuses on a specific target that delivers efficiently various operations in the design, modelling and animation of such surfaces.The project files will not be available online
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Geometric modelling and shape optimisation of pharmaceutical tablets. Geometric modelling and shape optimisation of pharmaceutical tablets using partial differential equations.
Pharmaceutical tablets have been the most dominant form for drug delivery and they need to be strong enough to withstand external stresses due to packaging and loading conditions before use. The strength of the produced tablets, which is characterised by their compressibility and compactibility, is usually deter-mined through a physical prototype. This process is sometimes quite expensive and time consuming. Therefore, simulating this process before hand can over-come this problem. A technique for shape modelling of pharmaceutical tablets based on the use of Partial Differential Equations is presented in this thesis. The volume and the sur-face area of the generated parametric tablet in various shapes have been es-timated numerically. This work also presents an extended formulation of the PDE method to a higher dimensional space by increasing the number of pa-rameters responsible for describing the surface in order to generate a solid tab-let. The shape and size of the generated solid tablets can be changed by ex-ploiting the analytic expressions relating the coefficients associated with the PDE method.
The solution of the axisymmetric boundary value problem for a finite cylinder subject to a uniform axial load has been utilised in order to model a displace-ment component of a compressed PDE-based representation of a flat-faced round tablet. The simulation results, which are analysed using the Heckel model, show that the developed model is capable of predicting the compressibility of pharmaceutical powders since it fits the experimental data accurately. The opti-mal design of pharmaceutical tablets with particular volume and maximum strength has been obtained using an automatic design optimisation which is performed by combining the PDE method and a standard method for numerical optimisation
Macro-mechanical modelling and simulation of textile fabric and clothing with S-FEM
Tese de Doutoramento Programa Doutoral em Engenharia TêxtilEsta tese propõe um método de elementos finitos, designado por S-FEM (Smoothed Finite Element
Method), para modelação e análise mecânica de estruturas têxteis planas. Neste enquadramento
teórico, supõe-se que a estrutura têxtil não-tecida é um material isotrópico elástico, enquanto a
estrutura têxtil tecida é um material elástico com anisotropia ortotrópica, para os quais as leis
constitutivas utilizam propriedades mecânicas de baixa pressão (low stress) com base na Medição
Objetiva de Tecidos (FOM - Fabric Objective Measurement).
As formulações de elementos finitos de baixa ordem baseadas em deslocamento quando aplicadas a
elementos finitos de placas (plate/shell) quadriláteras de 4 nós, incluindo campos de tensão de
cisalhamento transversal, baseiam-se nas contribuições de Raymond Mindlin e por Eric Reissner, no
que agora se designa teoria de deformação por cisalhamento de primeira ordem (first-order shear
deformation, do inglês, ou FSDT de forma abreviada), ou simplesmente teoria de Mindlin-Reissner, e
nas abordagens MITC (Mixed Interpolation of Tensorial Components), são nesta tese combinadas com
a técnica de suavização do/da gradiente/tensão nos termos dos modelos S-FEM por forma a mitigar
problemas como são o caso da distorção de elementos finitos, da granularidade grosseira da malha,
bem como dos bem conhecidos fenómenos de bloqueio. As malhas de quadriláteros são utilizadas
nesta tese devido à sua capacidade de representar geometrias complexas de tecidos em resultado de
deformações mecânicas como são os casos da recuperação face à pressão planar, flexão,
deformação, vibração, drapejamento, etc.
Refira-se que foi desenvolvido e implementado em Matlab um software para os novos modelos de
elementos finitos, em grande medida devido à inexistência de modelos S-FEM em softwares de análise
de elementos finitos (finite element analysis ou FEA), lacuna esta que ocorre quer em softwares
comerciais, quer não comerciais, e até em códigos abertos. Exemplos numéricos para as aplicações
básicas de engenharia no que respeita à modelação mecânica de folhas de tecido fino e de folhas de
tecido de espessura média em estudos de casos típicos, como é o caso da recuperação face a pressão
planar, flexão, deformação e comportamento livre de vibrações, indicam que os elementos finitos
(plate/shell) desenvolvidos com a técnica de suavização de tensão e MITC acabam por aliviar os
efeitos de distorção dos elementos, a granularidade grosseira da malha e efeito de bloqueio na
modelação e análise mecânica de tecidos muito finos e até mesmo de tecidos de espessura média. Os modelos de elementos finitos de placas (plate/shell) desenvolvidos durante o trajeto desta tese,
bem como as suas propriedades mecânicas de baixa tensão em termos de FOM, são, portanto, bem
adaptados à modelação e análise numérica de deformação macro-mecânica de folhas de tecido muito
fino e de folhas de tecido de espessura média, incluindo ao mesmo tempo análise de deformação
mecânica simples e complexa.An S-FEM (Smoothed Finite Element Method) for mechanical analysis and modelling of the textile
fabrics is proposed. In this theoretical framework, one assumes that the non-woven fabric is an elastic
isotropic material, while the woven fabric is an elastic with orthotropic anisotropy for which the
constitutive laws formulated are using low-stress mechanical properties based on FOM (Fabric
Objective Measurement). The displacement-based low-order finite element formulations for four-node
quadrilateral plate/shell finite element, including assumed transverse shear strain fields, are based
on the contributions of Raymond Mindlin and by Eric Reissner as FSDT (first-order shear deformation
theory and so-called the Mindlin-Reissner theory) together with MITC (Mixed Interpolation of Tensorial
Components) approaches, which are combined with the gradient/strain smoothing technique in terms
of S-FEM models contributed by G. R. Liu et al. in order to mitigate problems as element distortion,
mesh coarseness as well as the well-known locking phenomena. Quadrilateral meshes are used due
to ability to represent complicated geometries of complex mechanical deformation of the fabric such
as plane stress recovery, bending, buckling, vibration, draping behavior, etc. The finite element
computer codes were developed in MATLAB for the new formulated plate/shell finite element models
due to the lack of FEM (Finite Element Method) packages for S-FEM models in both commercial and
non-commercial FEA (Finite Element Analysis) computer applications, and even from open-source
platforms. Numerical examples for the basic engineering applications of mechanical modelling of thin
to moderately thick fabric sheet in the typical case studies such as in-plane stress recovery, bending,
buckling and free-vibration behavior, indicate that the developed plate/shell finite elements with
assumed strain smoothing technique and MITC, do alleviate element distortion, mesh coarseness,
and locking effect even for mechanical analysis and modelling very thin to moderately thick fabric. The
developed plate/shell finite element models and low-stress mechanic properties in terms of FOM are,
therefore, well adapted for numerical analysis and modelling of macro-mechanical deformation of the
thin to moderately thick fabric sheet including both simple and complex mechanical deformation
analysis.EMECW L12 MOBILITY GRANT AWARD CONTRACT BTG_559
Grant agreement n 2009/1661-001 001EC
Real-time simulation and visualisation of cloth using edge-based adaptive meshes
Real-time rendering and the animation of realistic virtual environments and characters
has progressed at a great pace, following advances in computer graphics hardware
in the last decade. The role of cloth simulation is becoming ever more important in
the quest to improve the realism of virtual environments.
The real-time simulation of cloth and clothing is important for many applications
such as virtual reality, crowd simulation, games and software for online clothes shopping.
A large number of polygons are necessary to depict the highly
exible nature of
cloth with wrinkling and frequent changes in its curvature. In combination with the
physical calculations which model the deformations, the effort required to simulate
cloth in detail is very computationally expensive resulting in much diffculty for its
realistic simulation at interactive frame rates. Real-time cloth simulations can lack
quality and realism compared to their offline counterparts, since coarse meshes must
often be employed for performance reasons.
The focus of this thesis is to develop techniques to allow the real-time simulation of
realistic cloth and clothing. Adaptive meshes have previously been developed to act as
a bridge between low and high polygon meshes, aiming to adaptively exploit variations
in the shape of the cloth. The mesh complexity is dynamically increased or refined to
balance quality against computational cost during a simulation. A limitation of many
approaches is they do not often consider the decimation or coarsening of previously
refined areas, or otherwise are not fast enough for real-time applications.
A novel edge-based adaptive mesh is developed for the fast incremental refinement
and coarsening of a triangular mesh. A mass-spring network is integrated into
the mesh permitting the real-time adaptive simulation of cloth, and techniques are
developed for the simulation of clothing on an animated character
Research Reports: 1997 NASA/ASEE Summer Faculty Fellowship Program
For the 33rd consecutive year, a NASA/ASEE Summer Faculty Fellowship Program was conducted at the Marshall Space Flight Center (MSFC). The program was conducted by the University of Alabama in Huntsville and MSFC during the period June 2, 1997 through August 8, 1997. Operated under the auspices of the American Society for Engineering Education, the MSFC program was sponsored by the Higher Education Branch, Education Division, NASA Headquarters, Washington, D.C. The basic objectives of the program, which are in the 34th year of operation nationally, are: (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participants' institutions; and (4) to contribute to the research objectives of the NASA centers. The Faculty Fellows spent 10 weeks at MSFC engaged in a research project compatible with their interests and background and worked in collaboration with a NASA/MSFC colleague. This document is a compilation of Fellows' reports on their research during the summer of 1997. The University of Alabama in Huntsville presents the Co-Directors' report on the administrative operations of the program. Further information can be obtained by contacting any of the editors
2016 IMSAloquium, Student Investigation Showcase
Welcome to the twenty-eighth year of the Student Inquiry and Research Program (SIR)! This is a program that is as old as IMSA. The SIR program represents our unending dedication to enabling our students to learn what it is to be an innovator and to make contributions to what is known on Earth.https://digitalcommons.imsa.edu/archives_sir/1026/thumbnail.jp
Generative Mesh Modeling
Generative Modeling is an alternative approach for the description of three-dimensional shape. The basic idea is to represent a model not as usual by an agglomeration of geometric primitives (triangles, point clouds, NURBS patches), but by functions. The paradigm change from objects to operations allows for a procedural representation of procedural shapes, such as most man-made objects. Instead of storing only the result of a 3D construction, the construction process itself is stored in a model file. The generative approach opens truly new perspectives in many ways, among others also for 3D knowledge management. It permits for instance to resort to a repository of already solved modeling problems, in order to re-use this knowledge also in different, slightly varied situations. The construction knowledge can be collected in digital libraries containing domain-specific parametric modeling tools. A concrete realization of this approach is a new general description language for 3D models, the "Generative Modeling Language" GML. As a Turing-complete "shape programming language" it is a basis of existing, primitv based 3D model formats. Together with its Runtime engine the GML permits - to store highly complex 3D models in a compact form, - to evaluate the description within fractions of a second, - to adaptively tesselate and to interactively display the model, - and even to change the models high-level parameters at runtime.Die generative Modellierung ist ein alternativer Ansatz zur Beschreibung von dreidimensionaler Form. Zugrunde liegt die Idee, ein Modell nicht wie üblich durch eine Ansammlung geometrischer Primitive (Dreiecke, Punkte, NURBS-Patches) zu beschreiben, sondern durch Funktionen. Der Paradigmenwechsel von Objekten zu Geometrie-erzeugenden Operationen ermöglicht es, prozedurale Modelle auch prozedural zu repräsentieren. Statt das Resultat eines 3D-Konstruktionsprozesses zu speichern, kann so der Konstruktionsprozess selber repräsentiert werden. Der generative Ansatz eröffnet unter anderem gänzlich neue Perspektiven für das Wissensmanagement im 3D-Bereich. Er ermöglicht etwa, auf einen Fundus bereits gelöster Konstruktions-Aufgaben zurückzugreifen, um sie in ähnlichen, aber leicht variierten Situationen wiederverwenden zu können. Das Konstruktions-Wissen kann dazu in Form von Bibliotheken parametrisierter, Domänen-spezifischer Modellier-Werkzeuge gesammelt werden. Konkret wird dazu eine neue allgemeine Modell-Beschreibungs-Sprache vorgeschlagen, die "Generative Modeling Language" GML. Als Turing-mächtige "Programmiersprache für Form" stellt sie eine echte Verallgemeinerung existierender Primitiv-basierter 3D-Modellformate dar. Zusammen mit ihrer Runtime-Engine erlaubt die GML, - hochkomplexe 3D-Objekte extrem kompakt zu beschreiben, - die Beschreibung innerhalb von Sekundenbruchteilen auszuwerten, - das Modell adaptiv darzustellen und interaktiv zu betrachten, - und die Modell-Parameter interaktiv zu verändern
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