3D–2D Projective Registration of Free-Form Curves and Surfaces

Some medical interventions require knowing the correspondence between an MRI/CT image and the actual position of the patient. Examples occur in neurosurgery and radiotherapy, but also in video surgery (laparoscopy). We present in this paper three new techniques for performing this task without artificial markers. To do this, we find the 3D–2D projective transformation (composition of a rigid displacement and a perspective projection) which maps a 3D object onto a 2D image of this object. Depending on the object model (curve or surface), and on the 2D image acquisition system (X-Ray, video), the techniques are different but the framework is common:Results are presented on a variety of real medical data to demonstrate the validity of our approach.     

Connected component labeling on a 2D grid using CUDA

Connected component labeling is an important but computationally expensive operation required in many fields of research. The goal in the present work is to label connected components on a 2D binary map. Two different iterative algorithms for doing this task are presented. The first algorithm (Row-Col Unify) is based upon the directional propagation labeling, whereas the second algorithm uses the Label Equivalence technique. The Row-Col Unify algorithm uses a local array of references and the reduction technique intrinsically. The usage of shared memory extensively makes the code efficient. The Label Equivalence algorithm is an extended version of the one presented by Hawick et al. (2010) [3]. At the end the comparison depending on the performances of both of the algorithms is presented.     

利用三维矢量线条实现版画设计

设计了一种粗细变化的三维矢量线条,赋予了线条灵活的变化,可以改变局部的线宽、线条局部的走向和扭曲度等,并利用矢量线条的粗细变化来体现图像的灰度层次,从而达到模拟传统版画的效果;同时,给出了一种由曲线混合生成一定数目线距均匀曲线组的方法。     

3D Curves Reconstruction Based on Deformable Models

We present a new method, based on curve evolution, for the reconstruction of a 3D curve from two different projections. It is based on the minimization of an energy functional. Following the work on geodesic active contours by Caselles et al. (in Int. Conf. on Pattern Recognition, 1996, Vol. 43, pp. 693–737), we then transform the problem of minimizing the functional into a problem of geodesic computation in a Riemann space. The Euler-Lagrange equation of this new functional is derived and its associated PDE is solved using the level set formulation, giving the existence and uniqueness results. We apply the model to the reconstruction of a vessel from a biplane angiography.     

Model-Based Recognition of 3D Curves From One View

It is well known that there are no geometric invariants of a projection from 3D to 2D. However, given some modeling assumptions about the 3D object, such invariants can be found. The modeling assumptions should be sufficiently strong to enable us to find such invariants, but not stronger than necessary. In this paper we find such modeling assumptions for general 3D curves under affine projection. We show, for example, that if one of the two affine curvatures is known along the 3D curve, the other can be found from the curve's 2D image. We can also derive the point correspondence between the curve and its image. We also deal with point sets and direction vectors.     

基于遗传算法的多边形逼近3D数字曲线

首先对3D数字曲线进行简单的数据压缩．通过对该曲线上的点列进行二进制编码定义来表示数字曲线的染色体．二进制串中的每一个位称为基因,每一个逼近多边形和染色体形成1-1映射．目标函数使给定曲线和逼近多边形之间的均方差最小．构造了解决该问题的选择、交叉、变异三个算子．所得最优染色体中基因值为1的基因对应数字曲线的分界点．实验结果表明,该方法能够得到精确的逼近结果．     

Hoops: 3D Curves as Conservative Occluders for Cell-Visibility

Most visibility culling algorithms require convexity of occluders. Occluder synthesis algorithms attempt to construct large convex occluders inside bulky non-convex sets. Occluder fusion algorithms generate convex occluders that are contained in the umbra cast by a group of objects given an area light. In this paper we prove that convexity requirements can be shifted from the occluders to their umbra with no loss of efficiency, and use this property to show how some special non-planar, non-convex closed polylines that we call hoops can be used to compute occlusion efficiently for objects that have no large interior convex sets and were thus rejected by previous approaches.     

智能化三维表面粗糙度测量系统

针对我国现有的粗糙度测量仪器存在的问题及发展趋势,综合运用电子、机械、自动化等知识提出并设计了数字化、智能化方向的粗糙度测量系统;实现了探头的三维自动定位以及其运行机构,并采用了两个传感器同时测量待测零件轮廓和表面粗糙度的方式,简化了结构并提高了粗糙度测量仪的精度和性能.     

三维实体有限元自适应网格规划生成

为实现三维实体有限元网格自适应生成,设计了中心点、沿指定曲线和基于实体表面等网格加密生成方式;并根据分析对象几何特征和物理特性经验估计,以规划的方式构造自适应网格单元尺寸信息场．在此基础上,提出基于Delaunay剖分的动态节点单元一体化算法,生成几何特征和物理特性整体自适应的有限元网格．     

三维有限元网格的快速显示

应用OpengGL三维图形库,结合三维有限元网格的特点,提出了一种方便,实用的三维有限元网格的快速消隐显示方法,使得三维图形显示速度大为提高,并对显示中出现的网格线间断、缺线问题提出了相应的解决措施。     

基于二维隐曲线的动作补间新算法

参数曲线广泛应用于计算机动画,隐曲线在计算机动画中的应用也越来越受到重视.主要研究了二维隐曲线在动作补间技术中的应用,提出了一种新的二维隐曲线动作补间算法-速度插值算法.在算法中,隐曲线用于指定动画对象的运动路径.速度曲线用于描述动画对象的速度与时间关系,结合运动路径和运动速度,速度插值技术用来生成与速度相关的插值序列.同时,在Matlab中实现了算法.仿真结果表明,按算法生成的动作补间动画自然逼真,且算法具有交互性好、真实感强、普遍性高、稳定性高等特点.     

3D and 2D/3D holograms model

The estimating problem of 3D holograms orientation selectivity on angular, orthogonal, and azimuthal sensitivity parameters is formulated and solved. Tenfold increase of density 3D, 2D/3D holograms in comparison with 2D holograms at given selectivity for ones is shown in theory and experimentally.     

Optimization of 3D Objects Layout into a Multiply Connected Domain with Account for Shortest Distances

The layout of 3D objects into a multiply connected domain formed by a circular cylinder and right rectangular prisms is optimized. Constraints are imposed on the shortest distances between objects. In order to construct a mathematical model, the Φ-function technique is employed. A special approach is proposed to construct different starting points. The approach is based on solving an auxiliary problem with an increased dimension of the solution space. The numerical examples are given.     

Hough Transform for Detecting Space Curves in Digital 3D Models

We present and analyse the Hough transform (HT) to recognise and approximate space curves in digital models, a problem that is not currently addressed by the standard HT. Our method works on meshes and point clouds and applies to models even incomplete or affected by noise, thus being suitable for the analysis of digital models deriving from 3D scans. In our approach we take advantage of a recent HT formulation for algebraic curves to define both parametric and implicit space curve representations. We also provide a comparative analysis of the HT-based method when dealing with both curve representations, discussing the computational performance and the approximation accuracy of both strategies.

     

Taking a 2D educational title into 3D

Maturing software for creating real-time interactive 3D (3D/VR) and hardware enabling its delivery give us the chance to explore practical issues involved in making commercially viable 3D/VR content. In October 1996, The Learning Company released the educational title Logic Quest, built using Sense8's WorldToolKit software. One of the first commercial 3D/VR children's titles for Windows 95, Logic Quest provides an example of what is involved in converting a 2D title (Think Quick!) to 3D. Studying the process the company followed lets us evaluate some of the challenges and benefits of moving a 2D title to 3D