Papers by Alexander Pasko
The Visual Computer, 1995
Computers & Graphics, 2013
Morphological shape design is interpreted in this paper as a search for new shapes froma particul... more Morphological shape design is interpreted in this paper as a search for new shapes froma particular application domain
represented by a set of selected shape instances. This paper proposes a new foundation formorphological shape design
and generation. In contrast to existing generative procedures, an approach based on a user-controlled metamorphosis
between functionally based shape models is presented. A formulation of the pairwise metamorphosis is proposed
with a variety of functions described for the stages of deformation, morphing and offsetting. This formulation is then
extended to the metamorphosis between groups of shapes with user-defined, dynamically correlated and weighted
feature elements. A practical system was implemented in the form of plugin to Maya and tested by an industrial designer on a group of representative shapes from a particular domain.
Communications of the ACM, 2009
Computer Graphics Forum, 2010
In this paper, we address shape modelling problems, encountered in computer animation and compute... more In this paper, we address shape modelling problems, encountered in computer animation and computer games development that are difficult to solve just using polygonal meshes. Our approach is based on a hybrid-modelling concept that combines polygonal meshes with implicit surfaces. A hybrid model consists of an animated polygonal mesh and an approximation of this mesh by a convolution surface stand-in that is embedded within it or is attached to it. The motions of both objects are synchronised using a rigging skeleton. We model the interaction between an animated mesh object and a viscoelastic substance, which is normally represented in an implicit form. Our approach is aimed at achieving verisimilitude rather than physically based simulation. The adhesive behaviour of the viscous object is modelled using geometric blending operations on the corresponding implicit surfaces. Another application of this approach is the creation of metamorphosing implicit surface parts that are attached to an animated mesh. A prototype implementation of the proposed approach and several examples of modelling and animation with near real-time preview times are presented.
Computers & Graphics, 2010
Techniques based on interval and affine arithmetic and their modifications are shown to provide r... more Techniques based on interval and affine arithmetic and their modifications are shown to provide reliable function range evaluation for the purposes of surface interrogation. In this paper we present a technique for the reliable interrogation of implicit surfaces using a modification of affine arithmetic called revised affine arithmetic. We extend the range of functions presented in revised affine arithmetic by introducing affine operations for arbitrary functions such as set-theoretic operations with Rfunctions, blending and conditional operators. The obtained affine forms of arbitrary functions provide faster and tighter function range evaluation. Several case studies for operations using affine forms are presented. The proposed techniques for surface interrogation are tested using ray-surface intersection for ray-tracing and spatial cell enumeration for polygonisation. These applications with our extensions provide fast and reliable rendering of a wide range of arbitrary procedurally defined implicit surfaces (including polynomial surfaces, constructive solids, pseudo-random objects, procedurally defined microstructures, and others). We compare the function range evaluation technique based on extended revised affine arithmetic with other reliable techniques based on interval and affine arithmetic to show that our technique provides the fastest and tightest function range evaluation for fast and reliable interrogation of procedurally defined implicit surfaces.
Computer-Aided Design, 2011
Computers & Graphics, 1988
A use of the integrated computer geometry/graphics systems in the analysis of functions of three ... more A use of the integrated computer geometry/graphics systems in the analysis of functions of three variables (trivariate functions) is discussed. A method is obtained for the piecewise analytical description of the hypersurface defined by a trivariate function and of the isosurface of such a function. Algorithms for graphic presentation of the isosurface with hidden lines and surfaces removal are described. These algorithms are implemented at the SM-4 computer using the SAGRAF program complex.
The paper presents a novel approach for accurate polygonization of implicit surfaces with sharp f... more The paper presents a novel approach for accurate polygonization of implicit surfaces with sharp features. The approach is based on mesh evolution towards a given implicit surface with simultaneous control of the mesh vertex positions and mesh normals.
The Visual Computer, 2003
The paper presents a novel approach for accurate polygonization of implicit surfaces with sharp f... more The paper presents a novel approach for accurate polygonization of implicit surfaces with sharp features. The approach is based on mesh evolution towards a given implicit surface with simultaneous control of the mesh vertex positions and mesh normals. Given an initial polygonization of an implicit surface, a mesh evolution process initialized by the polygonization is used. The evolving mesh converges to a limit mesh which delivers a high quality approximation of the implicit surface. For analyzing how close the evolving mesh approaches the implicit surface we use two error metrics. The metrics measure deviations of the mesh vertices from the implicit surface and deviations of mesh normals from the normals of the implicit surface.
Computer-aided Design, 2001
Several techniques of computer-aided synthetic carving are presented. We describe both procedural... more Several techniques of computer-aided synthetic carving are presented. We describe both procedural methods for relief carvings and patterned lattices, as well as interactive carving. Different techniques of depth data generation for relief carving are described: polygon-to-function conversion, pattern-dependent interpolation, and ray-casting. All proposed methods are based on using implicit surfaces or, more generally, the function representation of geometric objects.
The Visual Computer, 1995
The Visual Computer, 1998
We present a general mathematical framework for transforming functionally defined shapes. The pro... more We present a general mathematical framework for transforming functionally defined shapes. The proposed model of extended space mappings considers transformations of a hypersurface in coordinate-function space with its projection onto geometric space. This model covers coordinate space mappings, metamorphosis, and algebraic operations on defining functions, and introduces several new types of transformations, such as function-dependent space mappings and combined mappings. The approach is illustrated by new local deformations created by means of function mappings, feature-based space mapping, offsetting along the normal, thin shell generation, 2D shape blending, and collision-free metamorphosis.
Computers & Graphics, 2000
A hybrid volume modeling system architecture is proposed. The key architectural decision of the s... more A hybrid volume modeling system architecture is proposed. The key architectural decision of the system design is based on the combination of volume representations by voxel data and by real continuous functions (so-called F-rep). We discuss the concept of the volume model, hybrid voxel-function representation, system input in different forms, and possible applications. Several examples illustrate the proposed approach: femur reconstruction and modeling, hybrid metamorphosis, collision detection, and real-time volumetric fly-through.
Techical Report 96-1-004, university of Aizu, Japan, 1996
Computer Graphics International ‘98, 1998
Surface creases provide us with important information about the shapes of objects and can be intu... more Surface creases provide us with important information about the shapes of objects and can be intuitively defined as curves on a surface along which the surface bends sharply. Our mathematical description of such surface creases is based on study of extrema of the principal curvatures along their curvature lines.
... Pasko Alexander Department of Digital Media Hosei University 3-7-2 Kajino-cho Koganei-shi Tok... more ... Pasko Alexander Department of Digital Media Hosei University 3-7-2 Kajino-cho Koganei-shi Tokyo 184-8584 Japan +81-42-387 ... modeling: concepts, implementation and applications", The Visual Computer, vol.11, No.8, 1995, pp.429-446 [3] Pasko A., Pilyugin V., Pokrovskiy V ...
Computer Graphics Forum, 2004
producing compressed yet precise data structures, thus providing inter-operability between curren... more producing compressed yet precise data structures, thus providing inter-operability between current and future computer platforms crucial to archiving. Examples of CSG reconstruction of historical temples and FRep modeling of traditional lacquer ware are given. We examine the application of fitting of a parameterized FRep model to a cloud of data points as a step towards automation of the modeling process. Virtual venues for public access to cultural heritage objects including real time interactive simulation of cultural heritage sites over the Web are discussed and illustrated.
The paper presents an approach to modeling heterogeneous objects as multidimensional point sets w... more The paper presents an approach to modeling heterogeneous objects as multidimensional point sets with multiple attributes (hypervolumes). A theoretical framework is based on a hybrid model of hypervolumes combining a cellular representation and a constructive representation using real-valued functions. This model allows for independent but unifying representation of geometry and attributes, and makes it possible to represent dimensionally non-homogeneous entities and their cellular decompositions. Hypervolume model components such as objects, operations and relations are introduced and outlined. The framework's inherent multidimensionality allowing, in particular, to deal naturally with time dependence promises to model complex dynamic objects composed of different materials with constructive building of their geometry and attributes. Attributes given at each point can represent properties of arbitrary nature (material, photometric, physical, statistical, etc.). To demonstrate a particular application of the proposed framework, we present an example of multimaterial modeling -a multilayer geological structure with cavities and wells. Another example illustrating the treatment of attributes other than material distributions is concerned with time-dependent adaptive mesh generation where function representation is used to describe object geometry and density of elements in the cellular model of the mesh. The examples have been implemented by using a specialized modeling language and software tools being developed by the authors.
This paper presents our approach to volume modelling which combines volume representations by vox... more This paper presents our approach to volume modelling which combines volume representations by voxel data and by continuous real functions. We discuss the main differences between direct volume visualization and modelling with voxel data, questions of conversion between two representations including volume reconstruction from contour data. We illustrate the approach by several advanced operations on a volumetric object: set-theoretic operations, sweeping, hypertexturing, feature-based sculpting, splitting, spatial and temporal transformations.
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Papers by Alexander Pasko
represented by a set of selected shape instances. This paper proposes a new foundation formorphological shape design
and generation. In contrast to existing generative procedures, an approach based on a user-controlled metamorphosis
between functionally based shape models is presented. A formulation of the pairwise metamorphosis is proposed
with a variety of functions described for the stages of deformation, morphing and offsetting. This formulation is then
extended to the metamorphosis between groups of shapes with user-defined, dynamically correlated and weighted
feature elements. A practical system was implemented in the form of plugin to Maya and tested by an industrial designer on a group of representative shapes from a particular domain.
represented by a set of selected shape instances. This paper proposes a new foundation formorphological shape design
and generation. In contrast to existing generative procedures, an approach based on a user-controlled metamorphosis
between functionally based shape models is presented. A formulation of the pairwise metamorphosis is proposed
with a variety of functions described for the stages of deformation, morphing and offsetting. This formulation is then
extended to the metamorphosis between groups of shapes with user-defined, dynamically correlated and weighted
feature elements. A practical system was implemented in the form of plugin to Maya and tested by an industrial designer on a group of representative shapes from a particular domain.