Issue 2
https://diglib.eg.org:443/handle/10.2312/67
Regular Issue2024-03-29T00:01:49ZOptimised CSG Tree Evaluation for Space Subdivision
https://diglib.eg.org:443/handle/10.2312/6959
Optimised CSG Tree Evaluation for Space Subdivision
Zemcik, Pavel; Chalmers, Alan
Ray tracing is a well known technique for producing realistic computer images. The computational requirements of this method are such that optimisation techniques, for example space subdivision, must be used if complex scenes are to be rendered in reasonable times. Constructive solid geometry (CSG) is a method for describing the geometry of complex scenes by applying set operations to primitive objects. The status tree approach has been used successfully within ray tracing to evaluate CSG structures. This paper proposes a combination of the status tree and space subdivision techniques as a means to improve further the efficiency of ray tracing.
1995-01-01T00:00:00ZFractals and Quasi-Affine Transformations
https://diglib.eg.org:443/handle/10.2312/6960
Fractals and Quasi-Affine Transformations
Nehlig, P. W.; Reveilles, J.-P.
In the continuum , contracting affine transformations have a unique fixed point. It is well known that this property is not preserved by dicretization and that the dynamics of discretized functions are very complicated. Discrete geometry allows us to start a theory for these dynamics and to illustrate some of their features by pictures. These pictures, rendered by a simple algorithm, reveal a very large spectrum of fractal structures, from the simplest to the intricatest.
1995-01-01T00:00:00ZFast Generation of Leakproof Surfaces from Well-Defined Objects by a Modified Marching Cubes Algorithm
https://diglib.eg.org:443/handle/10.2312/6958
Fast Generation of Leakproof Surfaces from Well-Defined Objects by a Modified Marching Cubes Algorithm
Roll, Stefan; Haase, Axel; von Kienlin, Markus
Local surface reconstruction by the Marching Cubes algorithm and its derivatives has a well known ambiguity, which prevents constructed surfaces from being closed and simple. We investigate this ambiguity assuming that a 3D image samples well-defined objects. In this case it is justified to aim at tiling of extracted object voxels rather than at reconstructing iso surfaces. Compared to iso surface reconstruction, our algorithm provides essentially the same level of confidence with respect to surface location at a lower computational cost. We present a leak detection and mending scheme which resolves the Marching Cubes ambiguity and guarantees a well-defined behaviour with respect to which objects are covered by which surface. We detail how to implement our leak mending method within a completely tabulated Marching Cubes algorithm. We finally give an example of how the adapted algorithm is of benefit to a recently developed 3D MR spectroscopy technique.
1995-01-01T00:00:00ZColouration Issues in Computer Generated Facial Animation
https://diglib.eg.org:443/handle/10.2312/6957
Colouration Issues in Computer Generated Facial Animation
Patel, M.
In everyday interactions with one another we use the face for recognising people and for communicating with them. Despite the considerable amount of research into computer generated facial animation, one particular aspect, that of the colouration of the face appears to have been neglected. In this paper we address issues pertinent to the use of colour for both modelling the appearance of the face and for enhancing communication during facial expression and animation. Colouration is an integral part of the face, which helps in the recognition of faces as well as in the interpretation of the often subtle signals emitted by the human face.
1995-01-01T00:00:00Z