Surface Deformation Method Research Articles

Feature sensitive deformation for triangular mesh models

Shape deformation is a useful tool for shape modeling and animation in computer graphics. In this paper, we propose a novel surface deformation method based on a feature sensitive (FS) metric. Firstly, taking unit normal vectors into account, we derive a FS Laplacian operator, which is more sensitive to featured regions of mesh models than existing operators. Secondly, we use the 1-ring tetrahedron in the dual mesh, a volumetric structure, to encode geometric details. To preserve the shape of the tetrahedron, we introduce linear tetrahedron constraints minimizing both the distortion of the base triangle and the change of the corresponding height. These ensure that geometric details are accurately preserved during deformation. The time complexity of our new method is similar to that of existing linear Laplacian methods. Examples are included to show that our FS deformation method better preserves mesh details, especially features, than existing Laplacian methods. Copyright © 2010 John Wiley & Sons, Ltd. (We propose a novel surface deformation method based on a feature sensitive (FS) metric. Using a FS Laplacian operator and the tetrahedron constraints, our new method preserves features of triangular meshes very well during deformation.)

Real time 3D simulation for nose surgery and automatic individual prosthesis design

This paper presents an intuitive nose surgery planning and simulation system, using 3D laser scan image and lateral X-ray image, to provide high quality prediction of the postoperative appearance, and design the patient specific prosthesis model automatically. After initial registration, the internal surface of soft tissue at the nose region was generated by the statistical data for soft tissue thickness adapted by the individual thickness information from the X-ray image. Then, the sketch contour of the 3D scan data on the lateral X-ray image was modified manually or adjusted automatically according to some aesthetic statistical data, to drive the simulation in real time by the state-of-the-art Laplacian surface deformation method. When satisfied with the 3D postoperative appearance, the deformation was mapped to the internal surface of soft tissue, and the change before and after simulation was utilized to generate the patient specific prosthesis model automatically. The surgeons who used the system confirmed that this planning system is attractive and has potential for daily clinical practice.

3D sketching for aesthetic design using fully free-form deformation features

This paper addresses the designers’ activity and in particular the way designers express an object shape in 2D sketches through character lines and how these lines form a basis for sketching shapes in 3D. The tools currently available in commercial CAS/CAD systems to manipulate the digital models are still not sufficiently suited to support design. In this paper, the so-called fully free-form deformation features ( δ-F 4) are introduced as a modelling method to take into account the curve-oriented stylists’ way of working. Both the advantages of a free-form surface deformation method and a feature-based approach are merged to define these high-level modelling entities allowing for a direct manipulation of surfaces through a limited number of intuitive parameters. Such features incorporate several characteristics designed to handle the uncertainties and/or inconsistencies of the designer's input during a sketching activity. In addition, a δ-F 4 classification is proposed to enable a fast access to the desired shape according to its semantics and characteristics.

Automated 3-D extraction and evaluation of the inner and outer cortical surfaces using a Laplacian map and partial volume effect classification

Accurate reconstruction of the inner and outer cortical surfaces of the human cerebrum is a critical objective for a wide variety of neuroimaging analysis purposes, including visualization, morphometry, and brain mapping. The Anatomic Segmentation using Proximity (ASP) algorithm, previously developed by our group, provides a topology-preserving cortical surface deformation method that has been extensively used for the aforementioned purposes. However, constraints in the algorithm to ensure topology preservation occasionally produce incorrect thickness measurements due to a restriction in the range of allowable distances between the gray and white matter surfaces. This problem is particularly prominent in pediatric brain images with tightly folded gyri. This paper presents a novel method for improving the conventional ASP algorithm by making use of partial volume information through probabilistic classification in order to allow for topology preservation across a less restricted range of cortical thickness values. The new algorithm also corrects the classification of the insular cortex by masking out subcortical tissues. For 70 pediatric brains, validation experiments for the modified algorithm, Constrained Laplacian ASP (CLASP), were performed by three methods: (i) volume matching between surface-masked gray matter (GM) and conventional tissue-classified GM, (ii) surface matching between simulated and CLASP-extracted surfaces, and (iii) repeatability of the surface reconstruction among 16 MRI scans of the same subject. In the volume-based evaluation, the volume enclosed by the CLASP WM and GM surfaces matched the classified GM volume 13% more accurately than using conventional ASP. In the surface-based evaluation, using synthesized thick cortex, the average difference between simulated and extracted surfaces was 4.6 ± 1.4 mm for conventional ASP and 0.5 ± 0.4 mm for CLASP. In a repeatability study, CLASP produced a 30% lower RMS error for the GM surface and a 8% lower RMS error for the WM surface compared with ASP.

Fully free-form deformation features for aesthetic shape design

Geometric models, such as B-Rep or CSG, are often used as a shared reference representation of the product along the whole design process. However, they do not provide capabilities for conveying complex information related to the involved product development tasks. This also applies for the initial styling activity, in which the shape is described by complex mathematical models handled by tools still not sufficiently suited to the creative designer mentality. To overcome these limits, we introduce the so-called Fully Free-Form Deformation Features (δ–F4) concept and the related manipulation tools. Advantages of both the free-form surface deformation method and the feature-based approach are combined to define these high-level modelling entities enabling the direct shape-oriented modification of surfaces through a restricted set of parameters. They are mainly defined by characteristic curves in order to better cope with the curve-oriented designers’ way of working. In addition, a (δ–F4) classification is proposed to enable a fast access to the desired shape. The proposed approach is illustrated with some examples from our prototype software.

Feature design on deformation of freeform surfaces using range control

This research is to develop a freeform surface design method which uses a feature-based design approach to process surface deformation. Using this method, called range control, a user modifies or changes the position of a characteristic control point of the control polyhedron for a Bspline surface, and regional surface deformation is then carried out through automatic displacements of a group of control points surrounding the characteristic point. The position changes of the group of control points are the interpolations of the maximum movement of the characteristic point related to a feature dimension and zero movements of some fixed points on the designated boundary. In this range control surface deformation method, three interpolating approaches are proposed to smooth out the changes between the characteristic vertex and fixed vertices. they are based on the linear interpolation under the consideration of index, distance and angle distributions. The ideas are implemented on a feature-based designing system for shoe lasts. Design examples are given to show that the range control method is simple, fast and practically applicable for shape deformation of freeform surfaces.