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.     

Real-time painting with an expressive virtual Chinese brush

Many painters today are going digital; because of the convenience and ease of experimentation that painting software gives. Our goal is to effectively simulate the process of brush painting - particularly the dynamics of a brush tuft - so that artists can use a virtual brush to paint with spirit - that is, in a lively, dynamic, brisk way. We've designed an efficient deformable brush model with spreading bristles that works in real time with consumer-level hardware. Our system renders realistic brushwork in response to input data captured from a device with six degrees of freedom (DOFs). Our research thus far focuses on brush modeling and ink depositing from brush to paper. The simulation of ink diffusion on paper, another important feature of Eastern brushwork, is a future goal.     

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.     

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.     

基于Gdiplus的笔迹回放系统

针对当前使用计算机创作的书法、绘画作品只能静态地展现最终效果,而无法记录中间创作过程的现状,设计开发一个基于Gdiplus的笔迹回放系统,能对创作过程中的运笔路线、运笔轻重、运笔缓急进行记录与回放。采用纹理融合技术为创作者提供炭精笔、水墨笔等多种笔触效果,以一种自定义的笔迹记录文件来保存整个创作过程。应用结果表明,该系统适用于教育领域,提供了一种保存艺术创作过程的解决方案。     

A virtual 3D interactive painting method for Chinese calligraphy and painting based on real-time force feedback technology

A novel 3D interactive painting method for Chinese calligraphy and painting based on force feedback technology is proposed. The relationship between the force exerted on the brush and the resulting brush deformation is analyzed and a spring-mass model is used to build a model of the 3D Chinese brush. The 2D brush footprint between the brush and the plane of the paper or object is calculated according to the deformation of the 3D brush when force is exerted on the 3D brush. Then the 3D brush footprint is obtained by projecting the 2D brush footprint onto the surface of the 3D object in real time, and a complete 3D brushstroke is obtained by superimposing 3D brush footprints along the painting direction. The proposed method has been successfully applied in a virtual 3D interactive drawing system based on force feedback technology. In this system, users can paint 3D brushstrokes in real time with a Phantom Desktop haptic device, which can effectively serve as a virtual reality interface to the simulated painting environment for users.     

Virtual hairy brush for digital painting and calligraphy

The art of Chinese calligraphy and painting has evolved incessantly over the long history of Chinese culture. It is a beautiful flower in the garden of traditional oriental art forms[1]. Since the emergence of modern computers, to design and develop an interactive and user friendly digital painting environment has been the long cherished dream for many researchers in computer graphics and human-computer interaction[2―10]. With the ever-increasing computing power of today’s hardware, researc…     

基于力反馈技术的三维模型表面绘制技术研究

本文将力反馈技术引入虚拟绘制过程中,提出一种基于力反馈技术的三维模型表面绘制方法。首先分析毛笔在三维绘制过程中的受力和变形,采用弹簧-振子模型建立三维毛笔模型;然后由毛笔碰撞变形后的最小包围球找出碰撞相关点,计算碰撞相关点的平均法矢确定投影平面,通过计算毛笔的变形得出在投影平面上的笔触,将该笔触投影到三维模型表面,同时控制毛笔的受力和运笔路径叠加笔触获得具有特定书法效果的三维笔道;最后介绍了仿真系统,使用Phantom Desktop力反馈设备在该系统中实现了三维模型表面的绘制。仿真结果表明,该方法再现了三维模型表面绘制的力觉控制过程,增强了绘制过程中的真实感。     

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...     

Video Painting via Motion Layer Manipulation

Temporal coherence is an important problem in Non‐Photorealistic Rendering for videos. In this paper, we present a novel approach to enhance temporal coherence in video painting. Instead of painting on video frame, our approach first partitions the video into multiple motion layers, and then places the brush strokes on the layers to generate the painted imagery. The extracted motion layers consist of one background layer and several object layers in each frame. Then, background layers from all the frames are aligned into a panoramic image, on which brush strokes are placed to paint the background in one‐shot. The strokes used to paint object layers are propagated frame by frame using smooth transformations defined by thin plate splines. Once the background and object layers are painted, they are projected back to each frame and blent to form the final painting results. Thanks to painting a single image, our approach can completely eliminate the flickering in background, and temporal coherence on object layers is also significantly enhanced due to the smooth transformation over frames. Additionally, by controlling the painting strokes on different layers, our approach is easy to generate painted video with multi‐style. Experimental results show that our approach is both robust and efficient to generate plausible video painting.     

Image palette: painting style transfer via brushstroke control synthesis

As one kind of technology of style transfer, painting style transfer can be used to render the sample images with a specific art style. With this technology, we can render the target images in the same style as the samples after some computation. We present a new approach of painting style transfer in which such a style transfer artwork is done by simulating the process of creation. We take the sample as a palette where users can select arbitrary contours or textures as the input brush strokes. We then analyze the style feature of the brush strokes and use this feature for synthesis and style transfer along the stroke curves learned from the specified area in target images or target 3D models to get the same painting style as the samples. Based on this approach, we also design and realize the corresponding painting system. The results show that the users can get a style-transferred personalized target image just by using the given sample images with the least interactions.     

Efficient example-based painting and synthesis of 2D directional texture

We present a new method for converting a photo or image to a synthesized painting following the painting style of an example painting. Treating painting styles of brush strokes as sample textures, we reduce the problem of learning an example painting to a texture synthesis problem. The proposed method uses a hierarchical patch-based approach to the synthesis of directional textures. The key features of our method are: 1) Painting styles are represented as one or more blocks of sample textures selected by the user from the example painting; 2) image segmentation and brush stroke directions defined by the medial axis are used to better represent and communicate shapes and objects present in the synthesized painting; 3) image masks and a hierarchy of texture patches are used to efficiently synthesize high-quality directional textures. The synthesis process is further accelerated through texture direction quantization and the use of Gaussian pyramids. Our method has the following advantages: First, the synthesized stroke textures can follow a direction field determined by the shapes of regions to be painted. Second, the method is very efficient; the generation time of a synthesized painting ranges from a few seconds to about one minute, rather than hours, as required by other existing methods, on a commodity PC. Furthermore, the technique presented here provides a new and efficient solution to the problem of synthesizing a 2D directional texture. We use a number of test examples to demonstrate the efficiency of the proposed method and the high quality of results produced by the method.     

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.     

基于图像语义分割的真实毛笔笔触实时生成技术

书法在文化传承中占据重要地位,书法书写笔迹的生成也一直是计算机图形学的研究重点和难点.现存基于模型和经验的方法,由于建模难度大,大都将笔触表述为简单的几何图形并且缺少变化,难以真实还原毛笔书写的笔触和笔迹.使得现存书法笔迹生成软件仅仅用于娱乐,而难以上升到数字化书法教育层面.文中从计算机视觉的角度出发,通过4个相机获取毛笔的实时书写图像;针对Deeplabv3+语义分割算法无法有效地分割小尺寸类别的缺点进行优化,使用优化的Deeplabv3+算法提取图像中毛笔笔头等关键信息,并通过Hough变换和PnP位姿估计算法计算笔杆相对位姿;基于位姿信息矫正和融合各相机笔触图像,提出一种未知区域估计方法估计相机无法拍摄到的笔触区域.按照不同条件提取400多幅书写图像作为数据集并进行实验结果表明,优化后的Deeplabv3+算法平均交并比(mean intersection-over-union,mIOU)达到0.849,与优化前相比提升了0.117;在小尺寸类别上交并比(intersection-over-union,IOU)达到0.59,提升了0.473.在保证实时性的前提下,最终生成的笔触与传统基于模型和经验的方法相比,可以更加真实地还原书写时的笔触,并避免对毛笔进行复杂的建模,为笔迹生成研究提供一种新的思路.     

基于经验的虚拟毛笔模型

书法艺术的计算机模拟吸引了越来越多的研究．为了达到中国书法艺术的实时仿真，给出了一种基于经验的虚拟毛笔模型．该模型着眼于实际书法的经验，可以克服基于粒子系统的虚拟毛笔的表达力匮乏和基于实体物理模型的虚拟毛笔的参数调整复杂性，并且避免了传统模型计算复杂的缺点．通过利用实际书法和国画过程的实验经验，虚拟毛笔可以高效地实时操作，并实现枯笔、飞白与渗透，得到可与真实毛笔笔迹媲美的效果．     

Droplet: A virtual brush model to simulate Chinese calligraphy and painting

This paper proposes a virtual brush model based on droplet operation to simulate Chinese calligraphy and traditional Chinese painting in real time. Two ways of applying droplet model to virtual calligraphy and painting are discussed in detail The second droplet model is more elaborated and can produce more vivid results while being slightly more time-consuming. The novel feature of the proposed droplet virtual brush model successfully enables the simulation painting system to overcome the poor expressional ability of virtual brush based on particle system and avoids the complex evaluation of physical brush with solid model. The model, derived from the actual calligraphy and painting experience, due to the simplicity of the droplet operation and its powerful expressive ability, considerably improves the performance of the simulation system and maintains painting effect comparable with real brush by supporting special Chinese brush effect such as dry brush, feng and stroke diffusion.     

Direct volume editing

In this work we present basic methodology for interactive volume editing on GPUs, and we demonstrate the use of these methods to achieve a number of different effects. We present fast techniques to modify the appearance and structure of volumetric scalar fields given on Cartesian grids. Similar to 2D circular brushes as used in surface painting we present 3D spherical brushes for intuitive coloring of particular structures in such fields. This paint metaphor is extended to allow the user to change the data itself, and the use of this functionality for interactive structure isolation, hole filling, and artefact removal is demonstrated. Building on previous work in the field we introduce high-resolution selection volumes, which can be seen as a resolution-based focus+context metaphor. By utilizing such volumes we present a novel approach to interactive volume editing at sub-voxel accuracy. Finally, we introduce a fast technique to paste textures onto iso-surfaces in a 3D scalar field. Since the texture resolution is independent of the volume resolution, this technique allows structure-aligned textures containing appearance properties or textual information to be used for volume augmentation and annotation.     

Materialization of interactive stereoscopic artwork based on hand-painted images

This paper presents interactive stereoscopic artwork and an algorithm for natural artistic expression using hand-painted images expressed by the artist’s manual brush strokes. The system proposes a new interactive method that allows a viewer to experience the painting process representing the consecutive process of an actual artist’s oil painting. The combination of analog and digital techniques stimulates emotions of the audience. The system architecture is composed of the Kinect sensor, which recognizes the movement of the user, a module that generates real-time stereoscopic images, and a projection module that displays the generated image. The survey is conducted to evaluate the effects of the 3D modeling method and the artistic modeling method. The statistical result show that the proposed hand-painted method provides more artistic satisfaction to the viewers than the 3D modeling method.     

A Generic Pigment Model for Digital Painting

We propose a generic pigment model suitable for digital painting in a wide range of genres including traditional Chinese painting and water-based painting. The model embodies a simulation of the pigment-water solution and its interaction with the brush and the paper at the level of pigment particles; such a level of detail is needed for achieving highly intricate effects by the artist. The simulation covers pigment diffusion and sorption processes at the paper surface, and aspects of pigment particle deposition on the paper. We follow rules and formulations from quantitative studies of adsorption and diffusion processes in surface chemistry and the textile industry. The result is a pigment model that spans a continuum from the very wet to the very dry brush stroke effects. We also propose a new pigment mixing method based on machine learning techniques to emulate pigment mixing in real life as well as to support the creation of new artificial pigments. To experiment with the proposed model, we embedded the model in a sophisticated digital brush system. The combined system exhibits interactive speed on a modest PC platform. http://www.cs.hku.hk/~songhua/pigment provides supplementary materials for this paper.