Papers by Jarek Rossignac
Key b-morph trajectories (black) between the b-roundings (solid green and blue) of two non-compat... more Key b-morph trajectories (black) between the b-roundings (solid green and blue) of two non-compatible shapes. Incompatible features (dotted) were removed by the b-rounding. Note the trajectory fans reaching the circular caps that replace these incompatible features. Extended trajectories are faded. Right: Composite b-morph (yellow) and trajectories (faded) between incompatible shapes obtained by recursively b-rounding and morphing the original shapes with their b-roundings. We investigate tools for comparing and morphing between pairs of registered, nearly similar shapes, P and Q. The traditional (closest point) c-morph moves a point p of P at constant velocity towards a closest point q on Q. Our new (tangent ball) b-morph moves each point along a circular arc incident orthogonally onto both P and Q. The b-morph has several advantages over the c-morph: it is symmetric, orientation sensitive, and yields smaller travel distance and distortion. It may help to measure and exaggerate the...
Proceedings of the 1986 workshop on Interactive 3D graphics - SI3D '86, 1987
The success of solid modelling in industrial design depends on facilities for specifying and edit... more The success of solid modelling in industrial design depends on facilities for specifying and editing parameterized models of solids through user-friendly interaction with a graphical front-end. Systems based on a dual representation, which combines Constructive Solid Geometry (CSG) and Boundary representation (BRep), seem most suitable for modelling mechanical parts. Typically they accept a CSG-compatible input (Boolean combinations of solid primitives) and offer facilities for parameterizing and editing part definitions. The user need not specify the topology of the boundary, but often has to solve three-dimensional trigonometric problems to compute the parameters of rigid motions that specify the positions of primitive solids. A front-end that automatically converts graphical input into rigid motions may be easily combined with boundary-oriented input, but its integration in dual systems usually complicates the editing process and limits the possibilities of parameterizing solid definitions. This report proposes a solution based on three main ideas: (1) enhance the semantics of CSG representations with rigid motions that operate on arbitrary collections of sub-solids regardless of their position in the CSG tree, (2) store rigid motions in terms of unevaluated constraints on graphically selected boundary features, (3) evaluate constraints independently, one at a time, in user-specified order. The third idea offers an alternative to known approaches, which convert all constraints into a large system of simultaneous equations to be solved by iterative numerical methods. The resulting front-end is inadequate for solving problems where multiple constraints must be met simultaneously, but provides a powerful tool for specifying and interactively editing parameterized models of mechanical parts and mechanisms. The order in which constraints are evaluated may also be used as a language for specifying the sequence of assembly and setup operations. An implementation under way is based on the interpreter of a new object oriented programming language, enhanced with geometric classes. Constraint evaluation results in the activation of methods which compute rigid motions from surface information. The set of available methods may be extended by the users, and methods may be integrated in higher level functions whose algorithmic nature simplifies the treatment of degenerate cases. Graphic interaction is provided through a geometrical engine which lets the user manipulate shaded images produced efficiently from the CSG representation of solid models.
Given the start positions of a group of dancers, a choreographer specifies their end positions an... more Given the start positions of a group of dancers, a choreographer specifies their end positions and says: "Run!" Each dancer has the choice of his/her motion. These choices influence the perceived beauty (or grace) of the overall choreography. We report experiments with an automatic approach, SAMBA, that computes a pleasing choreography. Rossignac and Vinacua focused on affine motions, which, in the plane, correspond to choreographies for three independent dancers. They proposed the inverse of the Average Relative Acceleration (ARA) as a measure of grace and their Steady Affine Morph (SAM) as the most graceful interpolating motion. Here, we extend their approach to larger groups. We start with a discretized (uniformly time-sampled) choreography, where each dancer moves with constant speed. Each SAMBA iteration steadies the choreography by tweaking the positions of dancers at all intermediate frames towards corresponding predicted positions. The prediction for the position o...
Dynapack exploits space-time coherence to compress the consecutive frames of the 3D animations of... more Dynapack exploits space-time coherence to compress the consecutive frames of the 3D animations of triangle meshes of constant connectivity. Instead of compressing each frame independently (space-only compression) or compressing the trajectory of each vertex independently (time-only compression), we predict the position of each vertex v of frame f from three of its neighbors in frame f and from the positions of v and of these neighbors in the previous frame (space-time compression). We introduce here two extrapolating spacetime predictors: the ELP extension of the Lorenzo predictor, developed originally for compressing regularly sampled 4D data sets, and the Replica predictor. ELP may be computed using only additions and subtractions of points and is a perfect predictor for portions of the animation undergoing pure translations. The Replica predictor is slightly more expensive to compute, but is a perfect predictor for arbitrary combinations of translations, rotations, and uniform sc...
Journal of cardiovascular translational research, Jan 16, 2018
The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical... more The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical decision-making process. In its current state, surgical planning offers an accurate hemodynamic assessment of the pre-operative condition, provides anatomical constraints for potential surgical options, and produces decent post-operative predictions if boundary conditions are similar enough between the pre-operative and post-operative states. Moving forward, validation with post-operative data is a necessary step in order to assess the accuracy of surgical planning and determine which methodological improvements are needed. Future efforts to automate the surgical planning process will reduce the individual expertise needed and encourage use in the clinic by clinicians. As post-operative physiologic predictions improve, Fontan surgical planning will become an more effective tool to accurately model patient-specific hemodynamics.
Eurographics Conference on Graphics Hardware, Sep 5, 1992
Abstract: To comply with drafting practices and because shaded images do not always reveal the in... more Abstract: To comply with drafting practices and because shaded images do not always reveal the internal or hiddenstructures of 3D models, designers need wireframe images with hidden lines dashed and nonconlour tesselation edges removed. Software techniques for wireframe rendering of polyhedra that require the viewpoint-dependent identilication of the visible portions of intersection and contour (ie silhouette) edges are too slow for interactive applications. Hardware support in contemporary graphics pipelines is unavailable or at ...
Current solid modellers lack facilities for describing blends, i.e., smooth fillets and rounds be... more Current solid modellers lack facilities for describing blends, i.e., smooth fillets and rounds between surface features of mechanical parts. This paper discusses the issues that arise in the design of blending facilities for solid modellers, summarizes proposed approaches, and presents a new approach for incorporating constant radius blends, conceptually generated by rolling a sphere in contact with the surfaces 1i9 be blended, in modellers based on constructive solid geometry (CSG). Blending is a catch-all term used to denote the creation of fillets, rounds, and similar smooth, localized transitions between large-scale surface features of a solid object. The major types of blends encountered in practice can be categorized as follows: • Surfaces governed by strong Junctiona.l constraints. For example, the surface joining the wing of an aircraft to the fuselage must meet stringent aerodynamic requirements. • Esthetic blends. For example, the smooth transition surface between the body and the bottom of a wine glass is constrained by esthetic considerations, rather than by mechanical function. • Fairings [30], i.e., transition surfaces that are relatively large (when compared to the surface features being blended), and whose shape is neither strongly constrained by function nor by esthetics. Typically, fairings serve to connect functional features such as bearing housings. Many examples are found in automobile suspension parts, ducts and manifolds. • Rounds and fillets. These are relatively small transition surfaces whose shape is weakly constrained by function. They are found in almost all machined, cast or molded parts, and may serve to relieve stress
Proceedings of the Fifth Acm Symposium, Jun 1, 1999
Computers and Graphics, Aug 1, 2012
The Visual Computer, 2003
We present a technique designed aiming to improve the compression of the Edgebreaker CLERS string... more We present a technique designed aiming to improve the compression of the Edgebreaker CLERS string for large and regular meshes, where regularity is understood as the compactness of the distribution of vertex degrees. Our algorithm uses a specially designed context based coding to compress the CLERS sequence. It is exceptionally simple to implement and can easily incorporated into any existing Edgebreaker implementation which uses the Spirale Reversi algorithm for decompression. Experimental results show that our procedure is very fast (600,000 triangles per second on PIII 650MHz for decompression) and leads to compression rates which are, in most cases, superior to those previously reported for large meshes of high regularity.
The Annals of thoracic surgery, Jan 29, 2015
A Fontan Y-shaped graft using a commercially available aortoiliac graft has been used to connect ... more A Fontan Y-shaped graft using a commercially available aortoiliac graft has been used to connect the inferior vena cava (IVC) to the pulmonary arteries. This modification of the Fontan procedure seeks to improve hepatic flow distribution (HFD) to the lungs. However, patient-specific anatomical restrictions might limit the space available for graft placement. Altering the superior vena cava (SVC) positioning is hypothesized to provide more space for an optimal connection, avoiding caval flow collision. Computational modeling tools were used to retrospectively study the effect of SVC placement on Y-graft hemodynamics. Patient-specific anatomies (N = 10 patients) and vessel flows were reconstructed from retrospective cardiac magnetic resonance (CMR) images after Fontan Y-graft completion. Alternative geometries were created using a virtual surgery environment, altering the SVC position and the offset in relation to the Y-graft branches. Geometric characterization and computational flui...
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Papers by Jarek Rossignac