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1.
A level-set approach for the metamorphosis of solid models   总被引:8,自引:0,他引:8  
We present a new approach to 3D shape metamorphosis. We express the interpolation of two shapes as a process where one shape deforms to maximize its similarity with another shape. The process incrementally optimizes an objective function while deforming an implicit surface model. We represent the deformable surface as a level set (iso-surface) of a densely sampled scalar function of three dimensions. Such level-set models have been shown to mimic conventional parametric deformable surface models by encoding surface movements as changes in the grayscale values of a volume data set. Thus, a well-founded mathematical structure leads to a set of procedures that describes how voxel values can be manipulated to create deformations that are represented as a sequence of volumes. The result is a 3D morphing method that offers several advantages over previous methods, including minimal need for user input, no model parameterization, flexible topology, and subvoxel accuracy  相似文献   

2.
The authors introduce a technique for 3D surface reconstruction using elastic deformable-models. The model used is an imaginary elastic grid, which is made of membranous, thin-plate-type material. The elastic grid can bent, twisted, compressed, and stretched into any desired 3D shape, which is specified by the shape constraints derived automatically from images of a real 3D object. Shape reconstruction is guided by a set of imaginary springs that enforce the consistency in the position, orientation, and/or curvature measurements of the elastic grid and the desired shape. The dynamics of a surface reconstruction process is regulated by Hamilton's principle or the principle of the least action. Furthermore, a 1D deformable template that borders the elastic grid may be used. This companion boundary template is attracted/repelled by image forces to conform with the silhouette of the imaged object. Implementation results using simple analytic shapes and images of real objects are presented  相似文献   

3.
Parametric PDE techniques, which use partial differential equations (PDEs) defined over a 2D or 3D parametric domain to model graphical objects and processes, can unify geometric attributes and functional constraints of the models. PDEs can also model implicit shapes defined by level sets of scalar intensity fields. In this paper, we present an approach that integrates parametric and implicit trivariate PDEs to define geometric solid models containing both geometric information and intensity distribution subject to flexible boundary conditions. The integrated formulation of second-order or fourth-order elliptic PDEs permits designers to manipulate PDE objects of complex geometry and/or arbitrary topology through direct sculpting and free-form modeling. We developed a PDE-based geometric modeling system for shape design and manipulation of PDE objects. The integration of implicit PDEs with parametric geometry offers more general and arbitrary shape blending and free-form modeling for objects with intensity attributes than pure geometric models  相似文献   

4.
综合模糊技术和水平集方法,提出了基于水平集模型的3D表面重建的方法,为了使重建结果不受噪声影响且与模型初始位置无关,在模糊分割的基础上,引入了模糊外力,在该外力作用下模型能逼近任意复杂的物体表面;利用水平集方法使模型能重建任意拓扑结构的重杂物体,实验结果表明该方法的有效性。  相似文献   

5.
In this paper, we propose a framework to reconstruct 3D models from raw scanned points by learning the prior knowledge of a specific class of objects. Unlike previous work that heuristically specifies particular regularities and defines parametric models, our shape priors are learned directly from existing 3D models under a framework based on affinity propagation. Given a database of 3D models within the same class of objects, we build a comprehensive library of 3D local shape priors. We then formulate the problem to select as-few-as-possible priors from the library, referred to as exemplar priors. These priors are sufficient to represent the 3D shapes of the whole class of objects from where they are generated. By manipulating these priors, we are able to reconstruct geometrically faithful models with the same class of objects from raw point clouds. Our framework can be easily generalized to reconstruct various categories of 3D objects that have more geometrically or topologically complex structures. Comprehensive experiments exhibit the power of our exemplar priors for gracefully solving several problems in 3D shape reconstruction such as preserving sharp features, recovering fine details and so on.  相似文献   

6.
Symmetry is a common characteristic in natural and man‐made objects. Its ubiquitous nature can be exploited to facilitate the analysis and processing of computational representations of real objects. In particular, in computer graphics, the detection of symmetries in 3D geometry has enabled a number of applications in modeling and reconstruction. However, the problem of symmetry detection in incomplete geometry remains a challenging task. In this paper, we propose a vote‐based approach to detect symmetry in 3D shapes, with special interest in models with large missing parts. Our algorithm generates a set of candidate symmetries by matching local maxima of a surface function based on the heat diffusion in local domains, which guarantee robustness to missing data. In order to deal with local perturbations, we propose a multi‐scale surface function that is useful to select a set of distinctive points over which the approximate symmetries are defined. In addition, we introduce a vote‐based scheme that is aware of the partiality, and therefore reduces the number of false positive votes for the candidate symmetries. We show the effectiveness of our method in a varied set of 3D shapes and different levels of partiality. Furthermore, we show the applicability of our algorithm in the repair and completion of challenging reassembled objects in the context of cultural heritage.  相似文献   

7.
In this paper,a boundary element method is first applied to real-tim animation of deformable objects and to simplify data preparation.Next,the visibleexternal surface of the object in deforming process is represented by B-spline surface,whose control points are embedded in dynamic equations of BEM.Fi-nally,the above method is applied to anatomical simulation.A pituitary model in human brain,which is reconstructed from a set of anatomical sections, is selected to be the deformable object under action of virtual tool such as scapel or probe.It produces fair graphic realism and high speed performance.The results show that BEM not only has less computational expense than FEM,but also is convenient to combine with the 3D reconstruction and surface modeling as it enables the reduction of the dimensionality of the problem by one.  相似文献   

8.
Deformable isosurfaces, implemented with level-set methods, have demonstrated a great potential in visualization and computer graphics for applications such as segmentation, surface processing, and physically-based modeling. Their usefulness has been limited, however, by their high computational cost and reliance on significant parameter tuning. This paper presents a solution to these challenges by describing graphics processor (GPU) based algorithms for solving and visualizing level-set solutions at interactive rates. The proposed solution is based on a new, streaming implementation of the narrow-band algorithm. The new algorithm packs the level-set isosurface data into 2D texture memory via a multidimensional virtual memory system. As the level set moves, this texture-based representation is dynamically updated via a novel GPU-to-CPU message passing scheme. By integrating the level-set solver with a real-time volume renderer, a user can visualize and intuitively steer the level-set surface as it evolves. We demonstrate the capabilities of this technology for interactive volume segmentation and visualization.  相似文献   

9.
基于形变模型的3D表面自适应重建   总被引:9,自引:2,他引:7       下载免费PDF全文
结合形变模型和ACD方法提出了基于变形模型的3D表面自适应重建方法。同时引入了与图象统计特性有关的外力,使得表面重建结果与模型的初始位置无关,利用ACD方法使模型自适应地改变其拓扑结构;为了提高表面重建的程度和鲁棒性,提出了多尺度重建算法,该方法适用于形状、结构复杂的物体重建,实验结果证明了该方法的有效性。  相似文献   

10.
单视图三维重建在计算机视觉领域中是一个具有挑战性的问题. 为了提升现有三维重建算法重建后三维模型的精度, 本文除了提取图像全局特征之外还提取图像局部特征, 结合全局特征和局部特征并选取SDF (signed distance function)作为重建后的三维物体表达方式, 不仅提高了模型的精度, 生成了更高质量的3D形状, 还增强了模型的泛化能力, 使得深度模型可以以较高质量重建出其他物体种类. 实验结果表明, 本文提出的深度网络结构和3D形状表示方法与当今最先进的重建算法相比, 无论在重建后三维模型的效果还是新型物体的泛化中都有更好的表现.  相似文献   

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