GRAPHICAL COMPUTING METHOD ON FOUR-BAR LINKAGE(1)——Inflexion Circle,Focal Axis,Ball''''s Point,Centering-point Curve and Circling-point Curve For Four ISPs,Coupler Curves Based on Ball''''s Points——

By means of programs GTMPAC based- on generalized triangle method,analysis and synthesis of mechanism design in accordance with absolutely graphicalmethod( absolutely germetrical method) are developed.In this paper,we make aspecial study about centering- point curve and circling- point curve and couplercurves based on Ball's points.     

A Subdivision Scheme for Continuous-Scale B-Splines and Affine-Invariant Progressive Smoothing

Multiscale representations and progressive smoothing constitutean important topic in different fields as computer vision, CAGD,and image processing. In this work, a multiscale representationof planar shapes is first described. The approach is based oncomputing classical B-splines of increasing orders, andtherefore is automatically affine invariant. The resultingrepresentation satisfies basic scale-space properties at least ina qualitative form, and is simple to implement.The representation obtained in this way is discrete in scale,since classical B-splines are functions in , where k isan integer bigger or equal than two. We present a subdivisionscheme for the computation of B-splines of finite support atcontinuous scales. With this scheme, B-splines representationsin are obtained for any real r in [0, ), andthe multiscale representation is extended to continuous scale.The proposed progressive smoothing receives a discrete set ofpoints as initial shape, while the smoothed curves arerepresented by continuous (analytical) functions, allowing astraightforward computation of geometric characteristics of theshape.     

一种 G2 连续组合曲线的表示

针对 Bézier 曲线以及现有众多含形状参数的扩展 Bézier 曲线的 G2 拼接条件均对控制顶点有严 格要求的问题,拟提出一种 G2 连续组合曲线,其能综合 Bézier 与 B 样条方法的优点,其基函数具有显式表达 式,既具有 B 样条方法的自动光滑性,又能轻松拥有 Bézier 曲线的端点几何特征。为此,构造了一组含 6 个 参数的基函数,按照 3 次 Bézier 曲线的定义方式由之构造了基于 4 个控制顶点的曲线段,根据曲线段的拼接条 件,按照 3 次 B 样条曲线的定义方式构造了基于 4 点分段的组合曲线。基函数具有全正性,其同时包含 3 次 Bernstein 基函数和所有由内部节点重复度均为 1 的节点向量所确定的 3 次 B 样条基函数作为特例。曲线段具 有保凸性、端点位置以及形状可调性,其同时包含 3 次 Bézier 曲线和 3 次 B 样条曲线段作为特例。组合曲线 的定义方式自动保证了其整体 G2 连续,将部分参数取特定值,即可使其端点插值、端边相切,此时其中依然 存在用于调整内部形状的独立参数。按一定规则选取组合曲线中的参数,即可重构 C2 连续的 3 次 B 样条曲线。     

一种单幅图像及其辅助曲线的三维建模方法

针对单幅图像的三维建模存在对用户的建模意图还原度不高、模型不够真实的问题,提出了一种通过构造曲线和辅助曲线来创建三维模型的方法.离散图像并补全构造曲线,为每条构造曲线添加辅助曲线.寻找离散后构造曲线间的对称关系并设置对称平面,计算曲线在三维空间中的位置.移动、旋转辅助曲线,得到三维模型,根据特征点位置和类型组合三维模型.实验结果表明,该方法得到的三维模型较符合用户的建模意图,同时具有算法简单、建模速度快、实用性强等特点.     

Reinforcement Learning Based Data Fusion Method for Multi-Sensors

In order to improve detection system robustness and reliability, multi-sensors fusion is used in modern air combat. In this paper, a data fusion method based on reinforcement learning is developed for multi-sensors. Initially, the cubic B-spline interpolation is used to solve time alignment problems of multi-source data. Then, the reinforcement learning based data fusion (RLBDF) method is proposed to obtain the fusion results. With the case that the priori knowledge of target is obtained, the fusion accuracy reinforcement is realized by the error between fused value and actual value. Furthermore, the Fisher information is instead used as the reward if the priori knowledge is unable to be obtained. Simulations results verify that the developed method is feasible and effective for the multi-sensors data fusion in air combat.      

FitConnect: Connecting Noisy 2D Samples by Fitted Neighbourhoods

We propose a parameter‐free method to recover manifold connectivity in unstructured 2D point clouds with high noise in terms of the local feature size. This enables us to capture the features which emerge out of the noise. To achieve this, we extend the reconstruction algorithm HNN‐Crust , which connects samples to two (noise‐free) neighbours and has been proven to output a manifold for a relaxed sampling condition. Applying this condition to noisy samples by projecting their k‐nearest neighbourhoods onto local circular fits leads to multiple candidate neighbour pairs and thus makes connecting them consistently an NP‐hard problem. To solve this efficiently, we design an algorithm that searches that solution space iteratively on different scales of k. It achieves linear time complexity in terms of point count plus quadratic time in the size of noise clusters. Our algorithm FitConnect extends HNN‐Crust seamlessly to connect both samples with and without noise, performs as local as the recovered features and can output multiple open or closed piecewise curves. Incidentally, our method simplifies the output geometry by eliminating all but a representative point from noisy clusters. Since local neighbourhood fits overlap consistently, the resulting connectivity represents an ordering of the samples along a manifold. This permits us to simply blend the local fits for denoising with the locally estimated noise extent. Aside from applications like reconstructing silhouettes of noisy sensed data, this lays important groundwork to improve surface reconstruction in 3D. Our open‐source algorithm is available online.     

NURBS-enhanced line integration boundary element method for 2D elasticity problems with body forces

A NURBS-enhanced boundary element method for 2D elasticity problems with body forces is proposed in this paper. The non-uniform rational B-spline (NURBS) basis functions are applied to construct the geometry and the model can be reproduced exactly at all stages since the refinement will not change the shape of the boundary. Both open curves and closed curves are considered. The fields are approximated by the traditional Lagrangian basis functions in parameter space, rather than by the same NURBS basis functions for geometry approximation. The parametric boundary elements and collocation nodes are defined from the knot vector of the curve and the refinement of the NURBS curve is easy. Boundary conditions can be imposed directly since the Lagrangian basis functions have the property of delta function. In addition, most methods for the treatment of singular integrals in traditional boundary element method can be applied in the proposed method. To overcome the difficulty for evaluation of the domain integrals in problems with body forces, a line integration method is further applied in this paper to compute the domain integrals without additional volume discretizations. Numerical examples have shown the accuracy of the proposed method.     

一类代数-三角函数表示的空间PH 曲线及其应用

在代数-三角函数空间Ω=span{1,θ ···, θm+1, sinθ, cosθ, θsinθ, ···, θn cosθ}定义了一类 空间曲线。通过选取合适的积分核函数,该曲线在xy-平面上的投影具有内蕴表示或整条曲线是 PH 曲线。曲线的笛卡尔坐标可由预定义的核函数通过积分计算得到。此外,给出了不同核函数 表示的积分曲线的Hermite 插值算法。对给定的边界条件,积分核函数系数可通过求解方程组 得到。最后,利用PH 曲线设计了一族标架,并用于构造有理形式的扫掠曲面。实验表明,分 片定义的扫掠曲面在脊线处G1 连续,在其余连接处达到近似G1 连续。     

基于非均匀环境建模与三阶Bezier曲线的平滑路径规划

针对工作于复杂环境下的大型工装,本文提出了一种基于非均匀环境建模与三阶Bezier曲线的平滑路径规划算法,以指导工装的运动.在环境建模方面,利用四叉树建立环境的非均匀模型,能够有效压缩环境信息,提高搜索效率;在路径搜索方面,以非均匀环境模型为基础,提出一种距离启发搜索和信息素混合更新的蚁群算法,能够得到工装的安全可行路径点;在路径平滑方面,基于三阶Bezier曲线,提出能够连接任意位置和任意方向两点的转弯单元的设计方法,利用转弯单元连接路径搜索算法得到的路径点,能够获得满足工装非完整性约束的平滑路径.最后,以大型激光驱动器的靶场环境为对象,对本文算法的有效性和可靠性进行验证,并利用DELMIA平台进一步验证了规划路径的运动平滑性和安全性.     

Improved Corners with Multi‐Channel Signed Distance Fields

We propose an extension to the state‐of‐the‐art text rendering technique based on sampling a 2D signed distance field from a texture. This extension significantly improves the visual quality of sharp corners, which is the most problematic feature to reproduce for the original technique. We achieve this by using a combination of multiple distance fields in conjunction, which together provide a more thorough representation of the given glyph's (or any other 2D shape's) geometry. This multi‐channel distance field representation is described along with its application in shader‐based rendering. The rendering process itself remains very simple and efficient, and is fully compatible with previous monochrome distance fields. The introduced method of multi‐channel distance field construction requires a vector representation of the input shape. A comparative measurement of rendering quality shows that the error in the output image can be reduced by up to several orders of magnitude.