985 research outputs found
BSP-fields: An Exact Representation of Polygonal Objects by Differentiable Scalar Fields Based on Binary Space Partitioning
The problem considered in this work is to find a dimension independent algorithm for the generation of signed scalar fields exactly representing polygonal objects and satisfying the following requirements: the defining real function takes zero value exactly at the polygonal object boundary; no extra zero-value isosurfaces should be generated; C1 continuity of the function in the entire domain. The proposed algorithms are based on the binary space partitioning (BSP) of the object by the planes passing through the polygonal faces and are independent of the object genus, the number of disjoint components, and holes in the initial polygonal mesh. Several extensions to the basic algorithm are proposed to satisfy the selected optimization criteria. The generated BSP-fields allow for applying techniques of the function-based modeling to already existing legacy objects from CAD and computer animation areas, which is illustrated by several examples
An Exact Representation of Polygonal Objects by C1-continuous Scalar Fields Based on Binary Space Partitioning
The problem considered in this work is to find a dimension independent algorithm for the generation of signed scalar fields exactly representing polygonal objects and satisfying the following requirements: the defining real function takes zero value exactly at the polygonal object boundary; no extra zero-value isosurfaces should be generated; C1 continuity of the function in the entire domain. The proposed algorithms are based on the binary space partitioning (BSP) of the object by the planes passing through the polygonal faces and are independent of the object genus, the number of disjoint components, and holes in the initial polygonal mesh. Several extensions to the basic algorithm are proposed to satisfy the selected optimization criteria. The generated BSP-fields allow for applying techniques of function-based modelling to already existing legacy objects from CAD and computer animation areas, which is illustrated by several examples
Solving constraints within a graph based dependency model by digitising a new process of incrementally casting concrete structures
The mechanisation of incrementally casting concrete structures can reduce the economic and environmental cost of the formwork which produces them. Low-tech versions of these forms have been designed to produce structures with cross-sectional continuity, but the design and implementation of complex adaptable formworks remains untenable for smaller projects. Addressing these feasibility issues by digitally modelling these systems is problematic because constraint solvers are the obvious method of modelling the adaptable formwork, but cannot acknowledge the hierarchical relationships created by assembling multiple instances of the system. This thesis hypothesises that these opposing relationships may not be completely disparate and that simple dependency relationships can be used to solve constraints if the real procedure of constructing the system is replicated digitally. The behaviour of the digital model was correlated with the behaviour of physical prototypes of the system which were refined based on digital explorations of its possibilities. The generated output is assessed physically on the basis of its efficiency and ease of assembly and digitally on the basis that permutations can be simply described and potentially built in reality. One of the columns generated by the thesis will be cast by the redesigned system in Lyon at the first F2F (file to factory) continuum workshop
Axial deformation with controllable local coordinate frames.
Chow, Yuk Pui.Thesis (M.Phil.)--Chinese University of Hong Kong, 2010.Includes bibliographical references (leaves 83-87).Abstracts in English and Chinese.Chapter 1. --- Introduction --- p.13-16Chapter 1.1. --- Motivation --- p.13Chapter 1.2 --- Objectives --- p.14-15Chapter 1.3 --- Thesis Organization --- p.16Chapter 2. --- Related Works --- p.17-24Chapter 2.1 --- Axial and the Free Form Deformation --- p.17Chapter 2.1.1 --- The Free-Form Deformation --- p.18Chapter 2.1.2 --- The Lattice-based Representation --- p.18Chapter 2.1.3 --- The Axial Deformation --- p.19-20Chapter 2.1.4 --- Curve Pair-based Representation --- p.21-22Chapter 2.2 --- Self Intersection Detection --- p.23-24Chapter 3. --- Axial Deformation with Controllable LCFs --- p.25-46Chapter 3.1 --- Related Methods --- p.25Chapter 3.2 --- Axial Space --- p.26-27Chapter 3.3 --- Definition of Local Coordinate Frame --- p.28-29Chapter 3.4 --- Constructing Axial Curve with LCFs --- p.30Chapter 3.5 --- Point Projection Method --- p.31-32Chapter 3.5.1 --- Optimum Reference Axial Curve Point --- p.33Chapter 3.6 --- Advantages using LCFs in Axial Deformation --- p.34Chapter 3.6.1 --- Deformation with Smooth Interpolated LCFs --- p.34-37Chapter 3.6.2 --- Used in Closed-curve Deformation --- p.38-39Chapter 3.6.3 --- Hierarchy of Axial Curve --- p.40Chapter 3.6.4 --- Applications in Soft Object Deformation --- p.41Chapter 3.7 --- Experiments and Results --- p.42-46Chapter 4. --- Self Intersection Detection of Axial Curve with LCFs --- p.47-76Chapter 4.1 --- Related Works --- p.48-49Chapter 4.2 --- Algorithms for Solving Self-intersection Problem with a set of LCFs --- p.50-51Chapter 4.2.1 --- The Intersection of Two Plane --- p.52Chapter 4.2.1.1 --- Constructing the Normal Plane --- p.53-54Chapter 4.2.1.2 --- A Line Formed by Two Planes Intersection --- p.55-57Chapter 4.2.1.3 --- Problems --- p.58Chapter 4.2.1.4 --- Sphere as Constraint --- p.59-60Chapter 4.2.1.5 --- Intersecting Line between Two Circular Discs --- p.61Chapter 4.2.2 --- Distance between a Mesh Vertex and a Curve Point --- p.62-63Chapter 4.2.2.1 --- Possible Cases of a Line and a Circle --- p.64-66Chapter 4.3 --- Definition Proof --- p.67Chapter 4.3.1 --- Define the Meaning of Self-intersection --- p.67Chapter 4.3.2 --- Cross Product of Two Vectors --- p.68Chapter 4.4 --- Factors Affecting the Accuracy of the Algorithm --- p.69Chapter 4.3.1 --- High Curvature of the Axial Curve --- p.69-70Chapter 4.3.2 --- Mesh Density of an Object. --- p.71-73Chapter 4.5 --- Architecture of the Self Intersection Algorithm --- p.74Chapter 4.6 --- Experimental Results --- p.75- 79Chapter 5. --- Conclusions and Future Development --- p.80-82Chapter 5.1 --- Contribution and Conclusions --- p.80-81Chapter 5.2 --- Limitations and Future Developments --- p.82References --- p.83-8
Branching Boogaloo: Botanical Adventures in Multi-Mediated Morphologies
FormaLeaf is a software interface for exploring leaf morphology using parallel string rewriting grammars called L-systems. Scanned images of dicotyledonous angiosperm leaves removed from plants around Bardās campus are displayed on the left and analyzed using the computer vision library OpenCV. Morphometrical information and terminological labels are reported in a side-panel. āSlider modeā allows the user to control the structural template and growth parameters of the generated L-system leaf displayed on the right. āVision modeā shows the input and generated leaves as the computer āseesā them. āSearch modeā attempts to automatically produce a formally defined graphical representation of the input by evaluating the visual similarity of a generated pool of candidate leaves. The system seeks to derive a possible internal structural configuration for venation based purely off a visual analysis of external shape. The iterations of the generated L-system leaves when viewed in succession appear as a hypothetical development sequence. FormaLeaf was written in Processing
Distance based heterogeneous volume modelling.
Natural objects, such as bones and watermelons, often have a heterogeneous composition and complex internal structures. Material properties inside the object can change abruptly or gradually, and representing such changes digitally can be problematic. Attribute functions represent physical properties distribution in the volumetric object. Modelling complex attributes within a volume is a complex task. There are several approaches to modelling attributes, but distance functions have gained popularity for heterogeneous object modelling because, in addition to their usefulness, they lead to predictability and intuitiveness. In this thesis, we consider a unified framework for heterogeneous volume modelling, specifically using distance fields. In particular, we tackle various issues associated with them such as the interpolation of volumetric attributes through time for shape transformation and intuitive and predictable interpolation of attributes inside a shape. To achieve these results, we rely on smooth approximate distance fields and interior distances. This thesis deals with outstanding issues in heterogeneous object modelling, and more specifically in modelling functionally graded materials and structures using different types of distances and approximation thereof. We demonstrate the benefits of heterogeneous volume modelling using smooth approximate distance fields with various applications, such as adaptive microstructures, morphological shape generation, shape driven interpolation of material properties through time and shape conforming interpolation of properties. Distance based modelling of attributes allows us to have a better parametrization of the object volume and design gradient properties across an object. This becomes more important nowadays with the growing interest in rapid prototyping and digital fabrication of heterogeneous objects and can find practical applications in different industries
Isosurface modelling of soft objects in computer graphics.
There are many different modelling techniques used in computer graphics to describe a wide range of objects and phenomena. In this thesis, details of research into the isosurface modelling technique are presented. The
isosurface technique is used in conjunction with more traditional modelling techniques to describe the objects needed in the different scenes of an animation. The isosurface modelling technique allows the description
and animation of objects that would be extremely difficult, or impossible to describe using other methods. The objects suitable for description using isosurface modelling are soft objects. Soft objects merge elegantly with each
other, pull apart, bubble, ripple and exhibit a variety of other effects. The representation was studied in three phases of a computer animation project: modelling of the objects; animation of the objects; and the production of the images. The research clarifies and presents many
algorithms needed to implement the isosurface representation in an animation system. The creation of a hierarchical computer graphics animation system
implementing the isosurface representation is described. The scalar fields defining the isosurfaces are represented using a scalar field description language, created as part of this research, which is automatically generated from the hierarchical description of the scene. This language has many techniques for combining and building the scalar field from a variety of components. Surface attributes of the objects are specified within the graphics system. Techniques are described which allow the handling of
these attributes along with the scalar field calculation. Many animation techniques specific to the isosurface representation are presented. By the conclusion of the research, a graphics system was created which elegantly handles the isosurface representation in a wide variety of
animation situations. This thesis establishes that isosurface modelling of soft objects is a powerful and useful technique which has wide application in the computer graphics community
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