22331464
Vector-City Vector Distance Transform
This paper will examine the current chamfer and vector distance transforms for encoding objects as distance fields. A new vector distance transform is introduced which uses the city-block chamfer distance transform as a basis. Detailed error analysis using real CT data is presented, demonstrating the improved accuracy of the new approach over existing methods. The production of a subvoxel accurate distance field is also demonstrated by employing an improved classification. Distance fields are shown for skull and chess piece datasets.
41482626
A New Approach to the Construction of Surfaces from Contour Data
This paper presents a new approach to the construction of a surface from a stack of contour slices. Unlike most existing methods, this new approach handles ambiguous conditions consistently without employing an algorithm to establish a correspondence between vertices on one contour and those on the next. It is easy to implement and fast to compute, requiring only basic geometric properties, namely closedness and simplicity, to be available with contour data. The advantages of this new approach have also been demonstrated with solutions to a few classical problems from the literature and some practical problems in medical imaging. It can also be applied to geographical surveying and keyframe animations.
6680702
Melting Objects
This paper describes a technique for producing realistic animations of melting objects. The work presented here introduces a method that accurately models both thermal flow and the latent heat during the phase change. The mechanism for energy transfer to the model is via both boundary conditions and radiation. Emphasis is made on accurately modelling the solid object and the method is particularly suited to rigid solids with complex surface geometry. The underlying objects are constructed using Volume Graphics modelling techniques (specifically voxelization), and a numerical simulation computes the time-dependent heat flow throughout the object. A technique for computing the phase transition is given, and details for rendering the melting objects are provided. The melting is controlled by material parameters, such as specific heat capacity, thermal conductivity, latent heat and temperature. Examples are given of melting ice and a plastic man.
1777796
A System for the Non-Linear Modelling of Deformable Procedural Shapes
This paper describes a fully interactive modelling system, which we have called ClayWorks, for defining the implicit geometry of 3D objects using parametric base primitives and deformations. The goal of this system is to provide a means for describing object data and its creation history by using a series of parametric steps that can be modified post-creation in a non-linearmanner. The advantages of this approach are that unlike other modelling approaches, it enables compact object descriptions, an intuitive modelling process, a simple approach to multiresolution objects, real-time feedback during the modelling process and a render independent object representation.
2872475
Texturing and hypertexturing of volumetric objects
Texture mapping is an extremely powerful and flexible tool for adding complex surface detail to an object. This paper introduces a method of surface texturing and hypertexturing complex volumetric objects in real-time. We employ distance field volume representations, texture based volume rendering and procedural texturing techniques with Shader Model 2.0 flexible programmable graphics hardware. We aim to provide a flexible cross-platform, non vendor specific implementation.
18996618
The Production of Volume Data from Triangular Meshes Using Voxelisation
Voxelisation is the term given to the process of converting data from one source type into a three dimensional volume of data values. The techniques known collectively as volume visualisation can then be applied to the data in order to produce a graphical representation of the object. This paper gives a practical approach to the voxelisation of data in the form of triangular meshes, and demonstrates the use of the method on various datasets. Visualisation is achieved by a method also described in the paper.
7924764
Organizing digital music for use: an examination of personal music collections
Current research on music information retrieval and music digital libraries focuses on providing access to huge, public music collections. In this paper we consider a different, but related, problem: supporting an individual in maintaining and using a personal music collection. We analyze organization and access techniques used to manage personal music collections (primarily CDs and MP3 files), and from these behaviors, to suggest user behaviors that should be supported in a personal music digital library (that is, a digital library of an individual’s personal music collection).
802922
Exploring Small Screen Digital Library Access with the Greenstone Digital Library
In recent years, the use of small screen devices has multiplied rapidly. This paper covers a number of different issues which arise when digital libraries are used in combination with such displays. Known limitations of small screens are presented to the Digital Library community. Two evaluations of pilot small-screen DL systems are presented, with some unexpected cultural and socio-technical concerns which arose. The pilot systems also demonstrate the delivery of small-screen access using an existing popular DL system.
9087296
Using Types to Parse Natural Language
We describe a natural language parser that uses type information to determine the grammatical structure of simple sentences and phrases. This stands in contrast to studies of type inference where types and grammatical structure play opposite roles, the former being determined by the latter. Our parser is implemented in Haskell and is based on a linguistic theory called applicative universal grammar (AUG). Our results should be interesting to computer scientists in the way in which AUG relates to types and combinatory calculus, and to linguists in the way in which a very simple, brute force parsing strategy performs surprisingly well in both performance and accuracy.
2346657
ML Typing, Explicit Polymorphism and Qualified Types
The ML type system was originally introduced as a means of identifying a class of terms in a simple untyped language, often referred to as core-ML, whose evaluation could be guaranteed not to “go wrong”. In subsequent work, the terms of core-ML have also been viewed as a ‘convenient shorthand’ for programs in typed languages. Notable examples include studies of ML polymorphism and investigations of overloading, motivated by the use of type classes in Haskell.
13870178
Simplifying and improving qualified types
Qualified types provide a general framework for constrained type systems, with applications including type class overloading, subtyping and record calculi. This paper presents an extended version of the type inference algorithm used in previous work, that can take account of the satisfiability of constraints to obtain more accurate principal types. The new algorithm is obtained by adding two new rules, one for simplification and one for improvement of constraint sets. In particular, it permits a better treatment for the previously troublesome multiple parameter extensions of Haskell type classes. For example, a form of parametric type classes, proposed by Chen, Hudak and Odersky, can be viewed as a special case of this work.