We argue that some algorithms are value-laden, and that two or more persons who accept different valuejudgments may have a rational reason to design such algorithms differently. We exemplify our claim by discussing a set of algorithms used in medical image analysis: In these algorithms it is often necessary to set certain thresholds for whether e.g. a cell should count as diseased or not, and the chosen threshold will partly depend on the software designer's preference between avoiding false positives and false negatives. This preference ultimately depends on a number of value-judgments. In the last section of the paper we discuss some general principles for dealing with ethical issues in algorithm-design.

No abstract

We present an algorithm for simulating the cracks found in Batik wax painting and dyeing technique used to make images on cloth. The algorithm produces cracks similar to those found in batik due to the wax cracking in the dyeing process. The method is unlike earlier simulation techniques used in computer graphics, in that it is based on the Distance Transform algorithm rather than on a physically based simulation such as using spring mass meshes or finite element methods. Such methods can be difficult to implement and computationally costly due to the large numbers of equations that need to be solved. In contrast, our method is simple to implement and takes only a few seconds to produce convincing patterns that capture many of the characteristics of the crack patterns found in real Batik cloth.

Free form deformations are useful for describing a class of complex motions within an animation system. Such deformations have been described using a generalization of parametric surfaces and their application to modeling is well documented. In this paper we present a method that can be applied to implicit sulfaces which are dejined as an iso-surjuce around U set of skeletal elements. The resulting surface is approximated by a polygon mesh. Shape distortions, such as "squash and stretch" are applied automatically to models in motion by warping the space in which the models exist. A model will change its shape as the function dejining the warped space can change over time ol; the model will deform as it moves through the warped space. Our system also treats groups of skeletal implicit primitives as CSG primitives. Warping can also be applied to these primitives. Different warp functions, for example bend, taper and twist can be applied locally or globally, the contribution from each primitive is calculated using a set of warp functions associated with that primitive. The interesting shapes, and possibly non-linear motion obtained from space warping, would be dificult to reproduce using other techniques.

A polygonisation algorithm is presented which extends an existing skeletal implicit surface technique to include operations based on Constructive Solid Geometry between blended groups of implicit surface objects. The result is a surface definition (to be called Boolean Compound Soft Object, or BCSO for short) which consists of a boolean expression with union, intersection, and set difference operators. The geometric primitives that form the operands are soft objects bounded by the iso-surfaces resulting from suitable potential fields. These potential fields are parameterized by configurations of so called skeletal elements. The resulting system, unlike most CSG systems, combines blended and unblended primitives. The polygonisation algorithm produces a mesh of triangles to facilitate fast viewing and rendering.