Gábor Renner | MTA Computer and Automation Research Institute (MTA SZTAKI) (original) (raw)
Papers by Gábor Renner
Springer eBooks, 2013
Class A surfaces are external surfaces of industrial objects, to which aesthetic appeal is attrib... more Class A surfaces are external surfaces of industrial objects, to which aesthetic appeal is attributed. Their design involves beyond functional criteria also subjective ones related to style and appearance. The design criteria include appropriate highlight line structures of the surfaces. Correction of highlight lines is usually performed interactively by the designer, which is time consuming, tedious and inaccurate. In the current paper an algorithmic method is suggested to automatically improve the quality of the highlight line structure. Application of the method is demonstrated by the correction of highlight line structure of industrial surfaces.
Highligh lines is a powerful method for quality evaluation and fine error disclosement of class A... more Highligh lines is a powerful method for quality evaluation and fine error disclosement of class A surfaces. We propose a tool that enables the designer to correct fine surface errors and improve the quality of class A surfaces, by adjusting its highlight lines. The adjustment is carried out by replacing the defective parts with highlight line curves of designer's intent. The parameters of the corrected surface, corresponding to the highlight line adjustment is determined by a genetic algorithm (GA). The paper discusses genetic representation and fitness function developed for the specific problem and gives an usability analysis of the method. The advantage of the method is its robustness and applicability to surfaces of any shapes, and any kinds of CAD representations.
In most of the graphics and design systems shape modification of free form surfaces is based on c... more In most of the graphics and design systems shape modification of free form surfaces is based on control point adjustment. Although this technique may work well, it is not sufficiently intuitive for a creative designer. Maintaining shape and design constraints can also be difficult. We propose a technique which is suitable to intuitively modify the shape of a parametric B-spline
Evaluation of quality is an important issue in the design of surfaces. Highlight lines is a highl... more Evaluation of quality is an important issue in the design of surfaces. Highlight lines is a highly sensitive method for quality control of free form surfaces. This paper presents a simple, robust and accurate method for the calculation of highlight lines. The generated highlight lines are suitable for appropriate evaluation of surface fine structure and for disclosure of irregularities of small extent. The method is applicable to any surface representations used in CAD systems.
Highlight lines are powerful in quality evaluation and disclosing errors of high quality surfaces... more Highlight lines are powerful in quality evaluation and disclosing errors of high quality surfaces. We propose a method that enables the designer to correct surfaces by adjusting their highlight lines. The adjustment of highlight line curves is carried out by replacing the defective parts with curves of the designer's intent. The corrected surface, which corresponds to the highlight line adjustment, is determined by a genetic algorithm (GA). The paper discusses genetic representation and fitness function developed for the specific problem and gives a usability analysis. The advantage of the method is its robustness and applicability to surfaces regardless of shape, and CAD representation. The method is meant to be applied in the final phase of shape modeling; its effectiveness is demonstrated by several industrial examples.
Computer Aided Design, Sep 1, 2007
The Medial Axis Transform surface, (or MAT or MS) is proving to be a useful tool for several appl... more The Medial Axis Transform surface, (or MAT or MS) is proving to be a useful tool for several applications and geometric reasoning tasks. However, calculation of the MAT is a time-consuming task and the benefits of the mathematical-based tool are offset by the cost of the calculation. This paper presents a method for medial surface calculation which uses subdivision to simplify the problem and hence speed up the calculation, a so-called 'divide-and-conquer' approach. The basis for this is a modification of the dual structure of the original object. As the calculation proceeds this structure is broken up into sub-pieces each representing a simpler sub-part of the MAT. Perhaps more importantly, this method creates a correct node decomposition of the dual structure. The paper goes on to demonstrate some applications of the results for geometric tasks, specifically offsetting and model subdivision, which are normally expensive but are simpler based on the MAT calculation results.
Product Modeling for Computer Integrated Design and Manufacture, 1997
Generating the MAT of a three-dimensional solid is a complicated and time consuming task. This pa... more Generating the MAT of a three-dimensional solid is a complicated and time consuming task. This paper presents methods of improving efficiency and reliability, first using detailed analysis of geometric cases to determine critical points and secondly using multiple start points for MAT surface calculation. Because of the requirement that the original object be planar the MAT surface is an approximation to the true MAT but it is possible to refine the MAT in a post-processing step to improve its quality.
Lecture Notes in Mechanical Engineering, 2018
The quality of the car-body surfaces is evaluated in the design phase. For that purpose, sensitiv... more The quality of the car-body surfaces is evaluated in the design phase. For that purpose, sensitive methods were developed; these are mainly the evaluation of the shape and distribution of reflection lines or highlight lines. In the paper, we propose a method to semi-automatically evaluate and improve the quality of the highlight line structures. Following the selection of the defective highlight line segments, the correction is carried out in two steps. First, sequences of evaluation points are computed to quantify the error in terms of distance and angle functions. Next, the corrected highlight points are calculated, and based on these points the corrected highlight line segments are constructed. The correspondence between the shape of the highlight lines and the surface parameters is highly complicated and strongly nonlinear. In the paper, a genetic process is proposed for the computation of the parameters of the surfaces, that corresponds to the corrected highlight line structure. Application of the method is demonstrated by correction of the highlight line structure and the shape of several car-body surfaces.
A new method for interpolation is presented which starts from a given set of data pints. The resu... more A new method for interpolation is presented which starts from a given set of data pints. The resulting curve consisting of a set of polynomials has tangent vector continuity in the nodes, and can have straight line sections incorporated in it, with preserved continuity properties. The interpolation is local in the sense, that the shape of the curve at a certain data pint is influenced by five data points in its neighbourhood. First the construction of tangent vectors, then the determination Of the parameter intervals are dealt with. These are selected in such a way that a quasi-natural parametrization is held along the whole curve.
Technical objects which are typically described by free-form surfaces, usually also contain conve... more Technical objects which are typically described by free-form surfaces, usually also contain conventional elements (planes, cylinders, cones). Consequently, methods and systems for defining free-form shapes are advantageously complemented by description of simple geometrical elements. In the paper, known methods of computational geometry are examined from the point of view of describing curves containing straight line sections. Moreover an analysis of the accuracy of approximating a circle by these methods i s given.
We present a novel system for building a 3D model of human knee based on a sequence MR images. Th... more We present a novel system for building a 3D model of human knee based on a sequence MR images. The system applies sophisticated modern image analysis and geometric modelling methods as well as graphical tools developed to investigate the morphology and functionality of human knee joint. The process of building a 3D model is described and illustrated by results for real measured data, followed by a discussion of system applications.
Computer Aided Geometric Design, 2002
In spite of extensive research on fitting parametric surfaces, the published 'standard' solutions... more In spite of extensive research on fitting parametric surfaces, the published 'standard' solutions often fail, when data points are irregularly distributed over topologically irregular domains, high accuracy is required and the free quantities of least squares fitting-such as the number and placement of knots, the weights of the smoothing functionals and the best parametrisation of the data points-must be set without user assistance. Further difficulties arise when the fitted surface needs to be extended in a natural way and hole loops without underlying point data need to be covered smoothly. This paper attempts to analyse the above difficulties and provide practical solutions to overcome these. Main results include algorithms to compute a good initial parametrisation, a fitting strategy to maintain tight tolerances and smoothness simultaneously, to handle weakly defined control points and a shape dependent knot refinement procedure. A few examples and suggestions for future work conclude the paper.
Curves and Surfaces, 1991
Abstract In this paper a concept is outlined for interpolating n-sided patches which consist of m... more Abstract In this paper a concept is outlined for interpolating n-sided patches which consist of making a G1 continuous connection between an arbitrary number of four-sided patches meeting at a common vertex point. First the cross derivative functions are defined, then a polynomial patch equation is constructed. The resulting patch is local in the sense that it depends only on the geometrical data of the boundary curve segments, and the other curve segments meeting at the vertices.
Springer eBooks, 2013
Class A surfaces are external surfaces of industrial objects, to which aesthetic appeal is attrib... more Class A surfaces are external surfaces of industrial objects, to which aesthetic appeal is attributed. Their design involves beyond functional criteria also subjective ones related to style and appearance. The design criteria include appropriate highlight line structures of the surfaces. Correction of highlight lines is usually performed interactively by the designer, which is time consuming, tedious and inaccurate. In the current paper an algorithmic method is suggested to automatically improve the quality of the highlight line structure. Application of the method is demonstrated by the correction of highlight line structure of industrial surfaces.
Highligh lines is a powerful method for quality evaluation and fine error disclosement of class A... more Highligh lines is a powerful method for quality evaluation and fine error disclosement of class A surfaces. We propose a tool that enables the designer to correct fine surface errors and improve the quality of class A surfaces, by adjusting its highlight lines. The adjustment is carried out by replacing the defective parts with highlight line curves of designer's intent. The parameters of the corrected surface, corresponding to the highlight line adjustment is determined by a genetic algorithm (GA). The paper discusses genetic representation and fitness function developed for the specific problem and gives an usability analysis of the method. The advantage of the method is its robustness and applicability to surfaces of any shapes, and any kinds of CAD representations.
In most of the graphics and design systems shape modification of free form surfaces is based on c... more In most of the graphics and design systems shape modification of free form surfaces is based on control point adjustment. Although this technique may work well, it is not sufficiently intuitive for a creative designer. Maintaining shape and design constraints can also be difficult. We propose a technique which is suitable to intuitively modify the shape of a parametric B-spline
Evaluation of quality is an important issue in the design of surfaces. Highlight lines is a highl... more Evaluation of quality is an important issue in the design of surfaces. Highlight lines is a highly sensitive method for quality control of free form surfaces. This paper presents a simple, robust and accurate method for the calculation of highlight lines. The generated highlight lines are suitable for appropriate evaluation of surface fine structure and for disclosure of irregularities of small extent. The method is applicable to any surface representations used in CAD systems.
Highlight lines are powerful in quality evaluation and disclosing errors of high quality surfaces... more Highlight lines are powerful in quality evaluation and disclosing errors of high quality surfaces. We propose a method that enables the designer to correct surfaces by adjusting their highlight lines. The adjustment of highlight line curves is carried out by replacing the defective parts with curves of the designer's intent. The corrected surface, which corresponds to the highlight line adjustment, is determined by a genetic algorithm (GA). The paper discusses genetic representation and fitness function developed for the specific problem and gives a usability analysis. The advantage of the method is its robustness and applicability to surfaces regardless of shape, and CAD representation. The method is meant to be applied in the final phase of shape modeling; its effectiveness is demonstrated by several industrial examples.
Computer Aided Design, Sep 1, 2007
The Medial Axis Transform surface, (or MAT or MS) is proving to be a useful tool for several appl... more The Medial Axis Transform surface, (or MAT or MS) is proving to be a useful tool for several applications and geometric reasoning tasks. However, calculation of the MAT is a time-consuming task and the benefits of the mathematical-based tool are offset by the cost of the calculation. This paper presents a method for medial surface calculation which uses subdivision to simplify the problem and hence speed up the calculation, a so-called 'divide-and-conquer' approach. The basis for this is a modification of the dual structure of the original object. As the calculation proceeds this structure is broken up into sub-pieces each representing a simpler sub-part of the MAT. Perhaps more importantly, this method creates a correct node decomposition of the dual structure. The paper goes on to demonstrate some applications of the results for geometric tasks, specifically offsetting and model subdivision, which are normally expensive but are simpler based on the MAT calculation results.
Product Modeling for Computer Integrated Design and Manufacture, 1997
Generating the MAT of a three-dimensional solid is a complicated and time consuming task. This pa... more Generating the MAT of a three-dimensional solid is a complicated and time consuming task. This paper presents methods of improving efficiency and reliability, first using detailed analysis of geometric cases to determine critical points and secondly using multiple start points for MAT surface calculation. Because of the requirement that the original object be planar the MAT surface is an approximation to the true MAT but it is possible to refine the MAT in a post-processing step to improve its quality.
Lecture Notes in Mechanical Engineering, 2018
The quality of the car-body surfaces is evaluated in the design phase. For that purpose, sensitiv... more The quality of the car-body surfaces is evaluated in the design phase. For that purpose, sensitive methods were developed; these are mainly the evaluation of the shape and distribution of reflection lines or highlight lines. In the paper, we propose a method to semi-automatically evaluate and improve the quality of the highlight line structures. Following the selection of the defective highlight line segments, the correction is carried out in two steps. First, sequences of evaluation points are computed to quantify the error in terms of distance and angle functions. Next, the corrected highlight points are calculated, and based on these points the corrected highlight line segments are constructed. The correspondence between the shape of the highlight lines and the surface parameters is highly complicated and strongly nonlinear. In the paper, a genetic process is proposed for the computation of the parameters of the surfaces, that corresponds to the corrected highlight line structure. Application of the method is demonstrated by correction of the highlight line structure and the shape of several car-body surfaces.
A new method for interpolation is presented which starts from a given set of data pints. The resu... more A new method for interpolation is presented which starts from a given set of data pints. The resulting curve consisting of a set of polynomials has tangent vector continuity in the nodes, and can have straight line sections incorporated in it, with preserved continuity properties. The interpolation is local in the sense, that the shape of the curve at a certain data pint is influenced by five data points in its neighbourhood. First the construction of tangent vectors, then the determination Of the parameter intervals are dealt with. These are selected in such a way that a quasi-natural parametrization is held along the whole curve.
Technical objects which are typically described by free-form surfaces, usually also contain conve... more Technical objects which are typically described by free-form surfaces, usually also contain conventional elements (planes, cylinders, cones). Consequently, methods and systems for defining free-form shapes are advantageously complemented by description of simple geometrical elements. In the paper, known methods of computational geometry are examined from the point of view of describing curves containing straight line sections. Moreover an analysis of the accuracy of approximating a circle by these methods i s given.
We present a novel system for building a 3D model of human knee based on a sequence MR images. Th... more We present a novel system for building a 3D model of human knee based on a sequence MR images. The system applies sophisticated modern image analysis and geometric modelling methods as well as graphical tools developed to investigate the morphology and functionality of human knee joint. The process of building a 3D model is described and illustrated by results for real measured data, followed by a discussion of system applications.
Computer Aided Geometric Design, 2002
In spite of extensive research on fitting parametric surfaces, the published 'standard' solutions... more In spite of extensive research on fitting parametric surfaces, the published 'standard' solutions often fail, when data points are irregularly distributed over topologically irregular domains, high accuracy is required and the free quantities of least squares fitting-such as the number and placement of knots, the weights of the smoothing functionals and the best parametrisation of the data points-must be set without user assistance. Further difficulties arise when the fitted surface needs to be extended in a natural way and hole loops without underlying point data need to be covered smoothly. This paper attempts to analyse the above difficulties and provide practical solutions to overcome these. Main results include algorithms to compute a good initial parametrisation, a fitting strategy to maintain tight tolerances and smoothness simultaneously, to handle weakly defined control points and a shape dependent knot refinement procedure. A few examples and suggestions for future work conclude the paper.
Curves and Surfaces, 1991
Abstract In this paper a concept is outlined for interpolating n-sided patches which consist of m... more Abstract In this paper a concept is outlined for interpolating n-sided patches which consist of making a G1 continuous connection between an arbitrary number of four-sided patches meeting at a common vertex point. First the cross derivative functions are defined, then a polynomial patch equation is constructed. The resulting patch is local in the sense that it depends only on the geometrical data of the boundary curve segments, and the other curve segments meeting at the vertices.