矢量画刷的设计与实现

在计算机上模拟现实中美术工作者使用的画刷一直是二维矢量编辑器必备的功能,本文介绍了如何在计算机上模拟绘图画刷的算法,其思想是将用户通过鼠标输入的一组离散的点转换成具有画刷风格的矢量图形,先对多边形画刷的外形定义,再对画刷的连续移动进行轨迹合成,最后实现特定的形状的画刷的轨迹。在此基础上实现了矩形、斜四边形、圆形画刷的算法设计。本文亦针对稠密的轨迹出现的自环绕现象,提出了反锯齿算法,并减少了自环绕圈数。实验测试结果表明,该算法效果良好,达到了预期目标。     

神奇的笔刷是如何炼成的？

在2012年第5期的PS秀场中。（《画浮云，用笔刷一秒搞定》），韩梅椿教小六用笔刷画出了生动的云彩。文章刊登后，很多朋友都用它画出了很多精彩的作品，也对笔刷的制作方法产生了兴趣。“我们能不能将自己喜欢的元素制作成笔刷呢？”当然可以!下面我们就让韩梅梅来讲解一下，这神奇的笔刷是如何制作出来的……     

无刷直流电机锁相环稳速系统建模与仿真

研究无刷直流电机高精度稳速系统中的转速、电流双闭环控制技术,采用了锁相环（PLL）技术用于无刷直流电机转速控制中。根据数学模型推导出了锁相环的传递函数并建立了仿真模型。在Matlab7．0／Simulink环境下,搭建了无刷直流电机双闭环锁相稳速系统仿真模型进行仿真,得出了速度阶跃响应的相电流、反电势、转速响应曲线以及转速波动曲线。仿真结果验证了各环节数学模型的有效性,证明了锁相环控制是提高无刷直流电机转速稳定度的有效手段。     

基于Dymola的无刷直流电机仿真模型

随着无刷直流电机的广泛应用,建立其仿真模型变得十分重要。使用新型的面向对象的仿真软件Dymola建立无刷直流电机仿真模型可以克服以往一些无刷直流电机模型的缺陷和不便之处。该文在分析无刷直流电机数学模型的基础上,建立了基于Dymola的无刷直流电机的仿真模型并进行了仿真试验,从而可以通过使用仿真模型来验证不同的控制策略和算法,对无刷直流电机的动,稳态进行分析,方便了无刷直流电机的分析和设计。     

基于运行时纹理合成的纹理画刷

纹理画刷是一种交互式纹理生成工具,能够在用户控制下生成所需要的纹理.本文提出了一种基于运行时纹理合成的纹理画刷实现算法.纹理合成采用逐块合成的方式,每次将整个样本图以选定的位移放置到合成图中,然后用Graph Cut来决定最终的输出区域.在预处理过程中计算得到两个相同样本图间的最佳切合位移集合,在合成过程中,贴块位移搜索范围限定在由此集合及用户控制所决定的一个很小的范围内,使合成速度达到实时.另外通过对"孤立块"采取"虚拟贴块法"选取贴块位移,较好地保持了画刷所生成纹理的一致性.实验结果表明该纹理画刷的纹理生成速度满足与用户交互的需求,且生成纹理的质量高.     

基于DSP无刷直流电机控制系统的研究及其仿真

无刷直流电机(BLDCM)是一个多变量、非线性系统。本文以无刷直流电机为研究对象,重点研究了无刷直流电机的控制系统及其仿真,并在最后对仿真结果进行了分析。在分析了无刷直流电机(BLDCM)的数学模型的基础上,文章中提出了一种以DSP芯片TMS320F2812为控制器的无刷直流电机双闭环控制设计的方案。文章中对此电机控制方案进行了软硬件的设计,并且在MATLAB上通过Simulink进行了系统仿真。仿真结果表明,控制系统运行平稳有较好的动态和静态特性,我们提出的控制方案正确可行。     

无刷直流电动机启动过程的Matlab仿真

该文主要讨论的是无刷直流电动机启动仿真。首先建立了无刷直流电动机的数学模型,然后详细讨论了无刷直流电动机的三相导通三相星形六状态下磁势随电流流向的改变而改变的情形并给出了启动过程的动态仿真。最后给出了仿真的结果。该文还讨论了电动机参数改变情况下的仿真结果的变化。     

无刷直流电动机启动过程的Matlab仿真

该文主要讨论的是无刷直流电动机启动仿真。首先建立了无刷直流电动机的数学模型,然后详细讨论了无刷直流电动机的三相导通三相星形六状态下磁势随电流流向的改变而改变的情形并给出了启动过程的动态仿真。最后给出了仿真的结果。该文还讨论了电动机参数改变情况下的仿真结果的变化。     

无刷直流电机控制系统的建模与仿真研究

在分析无刷直流电机动态数学模型的基础上,通过MATLAB建立了无刷直流电机控制系统的仿真模型,并通过对实例电机的仿真,给出了仿真结果,验证了模型的可行性.     

永磁无刷直流电机无位置传感器技术研究

永磁无刷直流电动机具有结构简单、效率高等优点,广泛应用于军工或其他领域,因此研究永磁无刷直流电动机具有重要的意义。首先介绍了永磁无刷直流电动机的工作原理,然后分析了无位置传感器永磁无刷直流电动机反电动势法原理,并设计了其无位置传感器控制系统。最后在Matlab/Simulink平台上搭建无位置传感器永磁无刷直流电动机双闭环PI控制系统的仿真模型,并给出了仿真结果。仿真结果表明该系统能够控制电动机正常启动,具有良好的动态和稳态性能。     

Suppression of electroosmotic flow by polyampholyte brush

Molecular dynamics simulations are conducted to investigate the suppression of electroosmotic flow by grafting polyampholyte brushes onto two parallel channel walls. The effects of grafting density and charge distribution of polyampholyte brushes on the electroosmotic flow velocity, salt ion distribution, and conformational characteristics of grafted brushes are studied in detail. Simulation results indicate that increasing the grafting density induces a stronger suppression of electroosmotic flow. The flow velocity is significantly influenced by the different charge distributions of polyampholyte brushes. In addition, an important flow phenomenon we have found is that the flow velocity profile shows a valley at the center of the channel. These results reveal that the flow velocity is dependent not only on the conformation of the polyampholyte brushes but also on the anion and cation distributions. The hierarchical distribution of salt ions is caused by the special properties of polyampholyte brushes.     

Twin Brush Floor Polishing Robot

A self-propulsive polishing robot is proposed as a method that automates a floor polisher and enables the omni-directional motion of a mobile robot without wheels. The proposed robot is composed of twin rotary brushes and does not require any mechanism such as driving wheels for the locomotion of the robot. When the robot polishes a floor with its brushes rotating, the friction forces occur between the brushes and the floor. The friction forces can be controlled by adjusting the posture of the brushes and it enables the robot to move in any desired direction.In this paper, we present a dynamics model of a brush, which corrects the errors of the currently existing model, and propose a new type of polishing robot, which has the twin brushes rotating in the opposite direction to each other. We also present the dynamics of the proposed robot and found the inverse dynamics solution for the omni-directional motion of the robot: we compute the values of the manipulating variables such as tilting directions and tilting amounts of the brushes for the translational, the rotational, and the combined general motion of the robot.     

Simulating oriental black-ink painting

“Soft” brushes respond elastically to the force exerted by an artist against the paper. When modeled, they effectively simulate oriental black-ink painting, eliminating unnatural spline curve editing. The interactive modeling algorithm for soft brushes lets users resize brushes and choose a particular color, texture, or type of bristles. With this unique approach, a user produces brush strokes by brush movement. Unlike the flat-brush based approach, here 3D visual information comes from the elastic deformation of bristles on the paper-crucial information in black-ink painting. We look first at the modeling process for soft brushes, then at how to effectively apply them in black-ink painting     

基于多尺度笔刷的分层油画风格化

基于图像的油画风格化绘制是计算机图形学领域非真实感绘制研究的热点之一.为了进一步提高图像油画风格化的质量,提出了一种基于多尺度笔刷的分层图像油画风格化绘制算法.该算法模拟艺术家的油画绘制过程,采用不同尺度的笔刷按照从粗到细的顺序逐层绘制.在每层笔刷绘制中,首先使用增量Voronoi序列采样点和图像切线方向场确定笔刷流线,然后结合笔刷形状与笔刷高度场进行纹理贴图,得到最终的图像油画风格化绘制结果.通过与现有算法比较,文中算法不仅能模拟真实的油画绘制过程,而且生成的油画效果层次感更强,充分体现了图像的结构特征和油画细节.     

Physically-based modeling of brush painting

This paper introduces physically-based modeling of brush painting. To provide the user with 3D brushes that can be manipulated and interact with the surface of the paper like real brushes, elastic bristles are designed and fixed at the bottom of the brush holder. A linear equation system is derived to calculate the physical deflection of bristles according to the force exerted on them from the surface of the paper. Our brushes provide naturalness in computer painting, and drastically decrease the designing complexity inherent in the conventional 2D outline-based painting.     

Cleaning a network with brushes

Following the decontamination metaphor for searching a graph, we introduce a cleaning process, which is related to both the chip-firing game and edge searching. Brushes (instead of chips) are placed on some vertices and, initially, all the edges are dirty. When a vertex is ‘fired’, each dirty incident edge is traversed by only one brush, cleaning it, but a brush is not allowed to traverse an already cleaned edge; consequently, a vertex may not need degree-many brushes to fire. The model presented is one where the edges are continually recontaminated, say by algae, so that cleaning is regarded as an on-going process. Ideally, the final configuration of the brushes, after all the edges have been cleaned, should be a viable starting configuration to clean the graph again. We show that this is possible with the least number of brushes if the vertices are fired sequentially but not if fired in parallel. We also present bounds for the least number of brushes required to clean graphs in general and some specific families of graphs.     

Adobe Photoshop CS巧用画笔工具

图像的绘制以及对图像进行局部修图是数字图像处理的一个重要问题,Adobe Photoshop CS中的画笔工具是绘图与修图工具组中的核心工具.本文分别介绍使用预设画笔类型、内置画笔类型、外置画笔类型以及自定义画笔的方式进行绘图;使用画笔的各种混合模式进行图像的局部修图;使用画笔工具沿路径进行描边、利用画笔工具修改蒙板以...     

Modulation of electroosmotic flow by electric field-responsive polyelectrolyte brushes: a molecular dynamics study

Molecular dynamics simulations were done to study the electroosmotic flow (EOF) transport in a nanochannel grafted with polyelectrolytes under the control of an electric field normal to the channel wall. This study first addresses some problems on the interplay between complex EOF and non-equilibrium conformational behavior of polyelectrolyte brushes at a molecular level. We demonstrated that changing the normal electric field has a significant impact on the conformational transition of polyelectrolytes and ion distributions, further leading to some new flow phenomena. The coupling mechanisms of polyelectrolyte chain dynamics and electrohydrodynamics were discussed. A remarkable result obtained is that fluid flux depends nonmonotonically on the normal electric field. Our work provides fundamental understanding of the EOF modulation using polyelectrolyte brushes and guidance for the design of smart nanofluidic channels.     

Brush up your painting skills

Most present-day interactive paint applications lack the means of adequately capturing a user’s gestures and translating them into realistic and predictable strokes, despite the importance of such a mechanism. We present a novel brush design that adopts constrained energy optimization to deform the brush tuft according to the user’s input movement. It incorporates bidirectional paint transfer and an anisotropic friction model. The main advantage of our method is its ability to handle a wide range of brush tuft shapes that are animated using a freeform deformation lattice, which is associated with the tuft’s geometry. This way, almost no conditions or limitations are placed upon the appearance of the brush. Examples range from round brushes modeled as polygon meshes, to flat brushes with individual bristles. Less common deformable tools that are used to apply or remove paint on the canvas, like sponges, can be created as well. The model is integrated in our interactive painting system for creating images with watery paint.     

Differential-Based Geometry and Texture Editing with Brushes

We present an interactive modeling framework for 3D shapes and for texture maps. The technique combines a differential-based deformation method with the idea of geometry brushes that allow to interactively apply modifications by painting on the geometry. Whereas most other deformation techniques demand the designer to define and move hard constrained regions on the surface, the proposed modeling process is similar to sculpting. Geometry brushes allow the user to locally manipulate the metric, enlarge, shrink or rotate parts of the surface and to generate bumps. In a similar way it is possible to modify texture maps, or more generally, arbitrary tensor maps on surfaces. The local modifications of the surface are integrated to a globally consistent deformation and visualized in real-time. While the geometry brushes are intended for local editing, the underlying technique can also be applied globally. We show how differentials may be modified for creating specific effects, like cartoonization of shapes or adjusting texture images.