Free-form Deformation Technique Research Articles

Reduced order model assisted evolutionary algorithms for multi-objective flow design optimization

Evolutionary algorithms (EAs) have been widely used for flow design optimization problems for their well-known robustness and derivative-free property as well as their advantages in dealing with multi-objective optimization problems and providing global optimal solutions. However, EAs usually involve a large number of function evaluations that are sometimes quite time consuming. In this article a reduced order modelling technique that combines proper orthogonal decomposition and radial basis function interpolation is developed to reduce the computational cost. These models provide an efficient way to simulate the whole flow region with varied geometry parameters instead of solving partial differential equations. As a test case, the design optimization of a heat exchanger is considered. Shape variation is conducted through a free form deformation technique, which deforms the computational grid employed by the flow solver. A comparison between the optimization results when using reduced order models and the exact flow solver is presented.

Automatic Generation of 3D Caricatures Based on Artistic Deformation Styles

Caricatures are a form of humorous visual art, usually created by skilled artists for the intention of amusement and entertainment. In this paper, we present a novel approach for automatic generation of digital caricatures from facial photographs, which capture artistic deformation styles from hand-drawn caricatures. We introduced a pseudo stress-strain model to encode the parameters of an artistic deformation style using "virtual" physical and material properties. We have also developed a software system for performing the caricaturistic deformation in 3D which eliminates the undesirable artifacts in 2D caricaturization. We employed a Multilevel Free-Form Deformation (MFFD) technique to optimize a 3D head model reconstructed from an input facial photograph, and for controlling the caricaturistic deformation. Our results demonstrated the effectiveness and usability of the proposed approach, which allows ordinary users to apply the captured and stored deformation styles to a variety of facial photographs.

義足ソケット形状決定のための下腿モデリングシステム(機械力学,計測,自動制御)

When the relationship between the dimensions of the crural area and those of the artificial leg socket is poor, it may cause problems, such as pressure sores in the crural area. This study discusses the mechanical characteristics at artificial leg socket interfaces. A computer-aided design (CAD) model of the crural area was constructed from ultrasonic three-dimensional measurements of a crural model, and a personalized CAD model of the crural area was constructed using a free-form deformation technique. Next, a finite element (FE) model of an artificial leg socket constructed using a preliminary design was synthesized as the leg model. Then, the mechanical behavior at the interface between the crural model and artificial leg socket was investigated using finite element method (FEM) analysis. When the socket was adjusted to the leg, the Von Mises stress at the bottom of the socket decreased. This also had the effect of holding the socket stably.

NPPV用鼻マスク装着部における応力解析のための個人対応FEモデルの構築(機械力学,計測,自動制御)

The number of patients with chronic respiratory deficiency, such as Chronic Obstructive Pulmonary Disease (COPD) or Sleep Apnea Syndrome (SAS), is increasing. For patients with comparatively serious symptoms, the Non-invasive Positive Pressure Ventilation (NPPV) may be prescribed. However, pressure necrosis or anaclisis could affect treatment by occurring at the contact area of nasal mask. In response to this problem, the construction of a simulation environment can be applied. The system consists of leaser measurement technology and ultrasonic and the Free Form Deformation (FFD) technique. The shape of the face is measured by laser technology, while ultrasonic technology is used to measure he shape of soft tissue and bone. This personal simulation model was created based on these measurement results and the interpolation results using the FFD. A fundamental numerical analysis was performed, and Von Mises stress distribution was shown when the NPPV nasal mask made contact with the face. This also compared with the actually measured results. In conclusion, the finite element model made by the proposed system can reproduce the actual stress state. By using this system, the shape of a nasal mask suitable for each patient can be determined.

Knowledge Extraction from Aerodynamic Design Data and its Application to 3D Turbine Blade Geometries

Applying numerical optimisation methods in the field of aerodynamic design optimisation normally leads to a huge amount of heterogeneous design data. While most often only the most promising results are investigated and used to drive further optimisations, general methods for investigating the entire design dataset are rare. We propose methods that allow the extraction of comprehensible knowledge from aerodynamic design data represented by discrete unstructured surface meshes. The knowledge is prepared in a way that is usable for guiding further computational as well as manual design and optimisation processes. A displacement measure is suggested in order to investigate local differences between designs. This measure provides information on the amount and direction of surface modifications. Using the displacement data in conjunction with statistical methods or data mining techniques provides meaningful knowledge from the dataset at hand. The theoretical concepts have been applied to a data set of 3D turbine stator blade geometries. The results have been verified by means of modifying the turbine blade geometry using direct manipulation of free form deformation (DMFFD) techniques. The performance of the deformed blade design has been calculated by running computational fluid dynamic (CFD) simulations. It is shown that the suggested framework provides reasonable results which can directly be transformed into design modifications in order to guide the design process.

Proportion-corrected scaled voxel models for Japanese children and their application to the numerical dosimetry of specific absorption rate for frequencies from 30 MHz to 3 GHz

The development of high-resolution anatomical voxel models of children is difficult given, inter alia, the ethical limitations on subjecting children to medical imaging. We instead used an existing voxel model of a Japanese adult and three-dimensional deformation to develop three voxel models that match the average body proportions of Japanese children at 3, 5 and 7 years old. The adult model was deformed to match the proportions of a child by using the measured dimensions of various body parts of children at 3, 5 and 7 years old and a free-form deformation technique. The three developed models represent average-size Japanese children of the respective ages. They consist of cubic voxels (2 mm on each side) and are segmented into 51 tissues and organs. We calculated the whole-body-averaged specific absorption rates (WBA-SARs) and tissue-averaged SARs for the child models for exposures to plane waves from 30 MHz to 3 GHz; these results were then compared with those for scaled down adult models. We also determined the incident electric-field strength required to produce the exposure equivalent to the ICNIRP basic restriction for general public exposure, i.e., a WBA-SAR of 0.08 W kg−1.

Free-Form Deformation with Rational DMS-Spline Volumes

In this paper, we propose a novel free-form deformation (FFD) technique, RDMS-FFD (Rational DMS-FFD), based on rational DMS-spline volumes. RDMS-FFD inherits some good properties of rational DMS-spline volumes and combines more deformation techniques than previous FFD methods in a consistent framework, such as local deformation, control lattice of arbitrary topology, smooth deformation, multiresolution deformation and direct manipulation of deformation. We first introduce the rational DMS-spline volume by directly generalizing the previous results related to DMS-splines. How to generate a tetrahedral domain that approximates the shape of the object to be deformed is also introduced in this paper. Unlike the traditional FFD techniques, we manipulate the vertices of the tetrahedral domain to achieve deformation results. Our system demonstrates that RDMS-FFD is powerful and intuitive in geometric modeling.

Mapping Melanoma Lymphoscintigraphy Data onto a 3D Anatomically Based Model

This study describes three-dimensional (3D) visualization of two-dimensional (2D) melanoma lymphatic mapping data, to provide a framework for analysis of melanoma spread patterns and a platform for recording new lymphoscintigraphy (LS) data more accurately in 3D. Specifically, the Sydney Melanoma Unit's LS database of over 5000 patients' primary cutaneous melanoma sites and sentinel lymph nodes have been mapped from 2D images onto a 3D anatomically based model. Anatomically accurate model geometries were created using the Visible Human dataset, giving a bicubic finite element skin mesh and discrete sentinel lymph node model. The full dataset of 2D melanoma site coordinates, excluding the head and neck, has been transformed onto this 3D skin mesh via free-form deformation and projection techniques. Sentinel lymph nodes were mapped onto the generic lymph node model for each patient. Preliminary spatial analysis indicates that a patient with a primary melanoma on the torso around the waist (on the standardized 3D model this region is 180 mm above and 130 mm below the umbilicus) with lymphatic drainage to the left axilla or left groin, will have a 17.7% probability of dual drainage to both node fields, with 95% confidence limits between 14.5 and 21.0%.

Interactive Virtual Hair-Dressing Room

Hair designing is one of crucial components of the hair simulation tasks. The efficiency of hair modeling is very much determined by the interactivity and the ease-to-use the designing tools within an application. This paper presents a unified framework that uses the various key techniques developed for specific tasks in hair simulation and to realize the ultimate goal of ‘virtual hair-dressing room’ that is simple to use but quite effective for generating fast hairstyles. Successful attempts have been made to handle the different challenging issues involved in simulation of hair at interactive rates. Effort has been put in developing methodologies for hair shape modeling, hair dynamics and hair rendering. A user friendly interface controlled by a haptic device facilitates designer’s interactivity with the hairstyles. Furthermore, designer’s visualization is enhanced by using real time animation and interactive rendering. Animation is done using a modified Free Form Deformation (FFD) technique that has been effectively adapted to various hairstyles. Hair Rendering is performed using an efficient scattering based technique, displaying hair with its various optical effects.

Identification of global modeshape from a few nodal eigenvectors using simple free-form deformation

A new method, different from common eigenvalue extraction methods, was proposed by Li and Kikuchi (in 8th ARC conference, 2002). It consists of explicit finite-element method and eigenvalue-extraction method in time domain. Even though the new method performs well in extracting eigenvalues, it is difficult to identify global modeshape of the given structure due to large size of time history data. Only some eigenvectors of a few nodal points can be extracted. In this paper, we apply computer animation technique to identify the global modeshape from a few nodal eigenvectors. Free-form deformation (FFD) technique is simply modified—simple FFD—and applied to the identification of global modeshapes. The basic concepts that consist of simple FFD algorithm are Delaunay triangulation and barycentric coordinate. Some numerical examples show good performance for the identification of global modeshape of a given structure.

A numerical approach for shape optimization of fluid flow domains

A numerical method for the shape optimization of fluid flow domains is presented and analyzed. The procedure is based on a flow solver, a mathematical optimization tool, and a technique for shape variation, which are combined into an integrated procedure. The flow solver relies on the discretization of the incompressible Navier–Stokes equations by means of the finite-volume method for block-structured, boundary-fitted grids with multi-grid acceleration. The optimization tool is an implementation of a trust region based derivative-free method. It is designed to minimize smooth functions whose evaluations are considered expensive and whose derivatives are not available or not desirable to approximate. The shape variation is obtained by deforming the computational grid employed by the flow solver. For this purpose, displacement fields scaled by the design variables are added to the initial grid. The displacement vectors are computed once before starting the optimization cycle by using a free-form deformation technique. Applications illustrating the functionality and the properties of the method are presented for some examples of engineering interest, such as the minimization of a pressure drop, the maximization of a lift force, and the optimization of a wall temperature.

Construction of FE Head Models Based on Japanese Head Shapes and Simulations of Impact Responses

The influence of the head shape on intracranial responses under impact was investigated by using Finite Element Method. Head shape models of 52 young adult male Japanese were analyzed by Multi Dimensional Scaling (MDS), and a 2 dimensional distribution map of head shapes was obtained. Four finite element models of the Japanese head were constructed by transformed finite element model of average American adult male (H-Head model) using Free Form Deformation technique. The constructed models represent 5%ile and 95%ile of the first 2 scales obtained by MDS. The same acceleration pulse was applied to H-Head model and the 4 finite element models. The cause of the difference was considered to be differences in pressure distribution in the brain caused by the differences in the head shape. Variation in the head shape should be taken into account in simulating the effects of impact using a finite element model.

Creation of Individual Head FE Model by the Composition of Representative Shapes

This paper suggests the method to create the individual finite element model by the dimensions only that can be measured easily. Individual head FE models are constructed by transformed a basic head FE head model with matched the individual head outer shape to the basic one by using Free Form Deformation (FED) technique. The individual head outer shape is created by weighted composition of the representative shapes of Japanese head calculated by the method combining Multi Dimensional Scaling (MDS) with FFD technique. Weights for the composition are calculated by minimizing the error between measured head dimensions and calculated ones. Furthermore, the construction method was validated by the comparison of the shape and pressure responses in brain of the head FE model created by the present method with those of the head FE model created from CT images. The suggested method can create individual FE model easily even when individual medical images (e.g. CT or MRI) cannot be taken.

多視点画像を用いたバーチャルクレイモデリングシステム

This paper proposes a “non-contact virtual clay modeling system.” We developed a prototype of a three-dimensional modeling system that allows users to shape “virtual clay” with their hand movements. In our proposed method, the users hand movements are observed with multiple cameras to estimate their positions. The human hand surface and the virtual clay are modeled by using subdivision surface. Using the estimated hand posisions, the virtual clay is shaped based on a direct free-form deformation technique. To achieve faster processing speed, we implemented the proposed system on a PC cluster. This implemented system proves the feasibility of an intuitive virtual clay modeling system.

GFFD: Generalized free-form deformation with scalar fields.

The novel free-form deformation(FFD) technique presented in the paper uses scalar fields defined by skeletons with arbitrary topology. The technique embeds objects into the scalar field by assigning a field value to each point of the objects. When the space of the skeleton is changed, the distribution of the scalar field changes accordingly, which implicitly defines a deformation of the space. The generality of skeletons assures that the technique can freely define deformable regions to produce a broader range of shape deformations.

Free-form design using axial curve-pairs

Deformation of 3D shapes usually requires the use of a deformation tool. The freeform deformation technique requires the use of a lattice of control point for deforming an object. This may require a synchronized movement of the lattice control points in order to obtain the desired effects. The axial deformation technique allows an object to be deformed by manipulating an axial curve. However, unexpected twist of the object may be obtained. This is a result of the lack of control on the local coordinate frame of the curve. This paper presents a technique for deforming objects with a set of axial curve-pairs. The use of a curve-pair allows the local coordinate frame to be controlled intuitively. A curve-pair is composed of a primary and an orientation curve. The orientation curve is an approximate offset of the primary curve. A technique is proposed for maintaining the relation between the primary and the orientation curve when the curve-pair is adjusted. By associating a complex 3D object to a curve-pair, the object can be stretched, bended, and twisted intuitively through manipulating the curve-pair. This deformation technique is particularly suitable for manipulating complex shapes (e.g. decorative components) in industrial and aesthetic design, and is also suitable for modelling characters and animals with flexible bodies. Adjusting the curve-pair according to some motion constraints produces different postures of a character or animal model. This in turn can be used as decorative components for aesthetic design.

Analysis of 3-D human foot forms using the Free Form Deformation method and its application in grading shoe lasts

An effective way to design well-fitting products is to analyse human body forms and to classify them into several groups. In the present study, a new method is proposed to analyse human body forms using the FFD (Free Form Deformation) technique. The FFD method is a way to deform the shapes of object smoothly by moving control lattice points set around the object. The reference body form is automatically deformed to coincide with the other body forms using the FFD method. The dissimilarity is defined by the movements of the control lattice points. The foot forms of 56 Japanese adult females were analysed with this method, and distributions for them were calculated using multi-dimensional scaling. The first axis contrasts feet with high dorsal arches and low dorsal arches, and the second axis is related to the antero-posterior proportion of the foot. As an application of the present method, a last of width EEEE was designed from an existing last of width E by applying the control lattice points that converted a representative foot of width E into a foot of width EEEE. The new EEEE width last reflected the allometric differences between narrow and wide feet better than one obtained by a conventional method. It was found that the present method with FFD is not only useful for classifying 3-D human body forms, but also has potential as applications for designing well-fitting products.

Applying Virtual Reality Techniques to Sensitivity-Based Structural Shape Design

Virtual reality (VR) provides a design space consisting of three-dimensional computer images where participants can interact with these images using natural human motions in real time. In the field of engineering design, prototyping and design verification have provided the initial application areas for VR. The research presented in this paper takes the scenario one step further by incorporating free-form deformation techniques and sensitivity analysis into the virtual world such that the designer can easily implement analysis-based shape design of a structural system where stress considerations are important. NURBS-based free-form deformation (NFFD) methods and direct manipulation techniques are used as the interface between the VR interaction and the finite element model. Sensitivity analysis is used to allow the designer to change the design model and immediately view the effects without performing a re-analysis. An engine connecting rod is analyzed to demonstrate how virtual reality techniques can be applied to structural shape design.

Shape optimization of continuum structures by genetic algorithm and boundary element method

This paper presents a new scheme for the shape optimization of continuum structures by using genetic algorithm (GA) and boundary element methods (BEM). The profiles of the objects under consideration are represented by the free-form deformation (FFD) technique. The chromosomes for the profiles are defined by considering as the genes the position vectors of the FFD control points. The population, which is constructed of many chromosomes, is modified by applying genetic operations such as the selection, the crossover and the mutation for determining a better profile for the design objectives. Besides, the objective functions are estimated by the BEM. Three schemes are presented in order to improve the computational efficiency of the present scheme. Finally, a cantilever beam under uniformly distributed load is considered as a numerical example.

遺伝アルゴリズムによる進化的形状設計法

In the CAD system, shape design or shape modeling is one of the bottle-necks because the shape design is a trial and error process, and it depends on designer's intuition and experience. Therefore, it is expected to develop an automatic shape design system or automatic shape design methodology. This paper presents methodology to generate the suitable shape automatically by using Genetic Algorithm (GA) and Free-Form Deformation (FFD). GA is one of the optimization techniques based on concepts from population genetics. To apply GA for shape design problem, arbitrary shapes must be coded as chromosomes and genetic operators (reproduction, crossover, mutation, etc.) should be defined for those chromosomes. In this paper, the lattice of the FFD is introduced as the chromosome of the shape. As the FFD technique, the shape is deformed by moving the positions of the control points of the FFD lattice. By this technique, the chromosome is expressed as a set of a few numbers of control points (floating point representations). Using GA and FFD, the genetic shape design system which permits user to define shape evaluation functions (fitness functions) is constructed. As the fitness functions, any technique can be used, such as FEM analysis, by the form of subroutine programs.