Artistic Surface Rendering Using Layout of Text

An artistic rendering method of free-form surfaces with the aid of half-toned text that is laid-out on the given surface is presented. The layout of the text is computed using symbolic composition of the free-form parametric surface  S(u, v)  with cubic or linear Bézier curve segments  C(t) = {c_u (t), c_v (t)}  , comprising the outline of the text symbols. Once the layout is constructed on the surface, a shading process is applied to the text, affecting the width of the symbols as well as their color, according to some shader function. The shader function depends on the surface orientation and the view direction as well as the color and the direction or position of the light source.     

Skeleton-enhanced line drawings for 3D models

We present a novel line drawing approach for 3D models by introducing their skeleton information into the rendering process. Based on the silhouettes of the input 3D models, we first extract feature lines in geometric regions by utilizing their curvature, torsion and view-dependent information. Then, the skeletons of the models are extracted by our newly developed skeleton extraction algorithm. After that, we draw the skeleton-guided lines from non-geometric regions through the skeleton information. These lines are combined with the feature lines to render the final line drawing result using the line optimization. Experimental results show that our algorithm can render line drawings more effectively with enhanced skeletons. The resulting artistic effects can capture the local geometries as well as the global skeletons of the input 3D models.     

针对全空子数据体的GPU体绘制

目的 体绘制是3维数据可视化的主要方法之一。用于体绘制的数据体中包含有大量的空体素,导致光线投射算法进行没有意义的重采样计算,必然降低绘制算法效率。针对全空子数据体体绘制低效问题,提出基于GPU体高效绘制方法。方法 利用八叉树数据结构组织数据,有效管理包含许多空体素的子数据体。通过绘制八叉树非全空叶子节点子数据体表面,使光线投射算法中起始和终止重采样位置更接近数据体中的可视部分,同时根据八叉树全空节点子数据体判定纹理查询结果,计算合适的跳跃步长,快速跳过八叉树中全空节点子数据体。结果 当数据体中空体素较多时,确定合适的八叉树深度,有效地跳过数据体中的空体素,减少体绘制运算量,实现对原基于体包围盒表面绘制的GPU光线投射算法的加速。结论 设计不透明度函数,凸显数据体中层位面,并将算法成功应用于地震数据可视化,取得很好应用效果。     

针对全空子数据体的GPU体绘制方法

体绘制是三维数据可视化的主要方法之一。用于体绘制的数据体中包含有大量的空体素,导致光线投射算法进行没有意义的重采样计算,必然降低绘制算法效率。针对全空子数据体体绘制低效问题,本文提出基于GPU体高效绘制方法。利用八叉树数据结构组织数据,有效管理包含许多空体素的子数据体。通过绘制八叉树非全空叶子结点子数据体表面,使光线投射算法中起始和终止重采样位置更接近数据体中的可视部分,同时根据八叉树全空结点子数据体判定纹理查询结果,计算合适的跳跃步长,快速跳过八叉树中全空结点子数据体,减少无效重采样点。当数据体中空体素较多时,实现对原基于体包围盒表面绘制的GPU光线投射算法的加速。设计不透明度函数,凸显数据体中层位面,并将算法成功应用于地震数据可视化,取得很好应用效果。     

基于图像的铅笔画绘制技术的研究现状与展望

非真实感绘制(Non-Photorcalistic Rendcring,NPR)是计算机图形学领域的一个分支,旨在使用计算机来生成具有某种艺术效果的作品。目前,非真实感绘制技术已经能够成功地模拟油画、水彩画、卡通画、铅笔画等艺术风格,在许多领域得到很广泛的应用。铅笔素描是艺术造型的基础。作为一种最简单的艺术表现形式,铅笔画凭借其简洁流畅的特点深受广大艺术爱好者的喜爱。如今,基于图像的铅笔画绘制技术已经是NPR领域的一个重要组成部分,受到诸多研究人员的关注,但该技术仍处于成长阶段,算法的通用性还无法满足现实应用的需求。     

Volumetric texture synthesis for non-photorealistic volume rendering of medical data

This paper presents a novel technique, called volumetric texture synthesis, for non-photorealistic volume rendering. It extends texture synthesis from 2D areas/3D surfaces to volumes. By selecting different texture samples, it allows for a wide variety of stylized rendering for the target volume. As a preprocessing step, volume data analysis is used to identify texture orientations for the volume. This is followed by volumetric texture synthesis, which generates 3D non-photorealistic textures along the identified texture orientations. Finally, standard volume rendering is applied to display the volume data decorated by the texture. Experimental results are provided in the paper.     

Pencil-like sketch rendering of 3D scenes using trajectory planning and dynamic tracking

Objective: We present a new non-photorealistic rendering method to render 3D scenes in the form of pencil-like sketches.Methods: This work is based on the observation that the dynamic feedback mechanism involving the human visual system and the motor control of the hand collectively generates the visual characteristics unique to hand-drawn sketches. At the heart of our approach is a trajectory planning and tracking algorithm that generate the sketch in multiple layers using a dynamic pen model. On each layer, a set of target strokes are generated from the silhouette lines, edges, and shaded regions which serve as the target trajectory for a closed-loop dynamic pen model. The pen model then produces the rendered sketch, whose characteristics can be adjusted with a set of trajectory and tracking parameters. This process continues in several layers until the tonal difference between the sketch and the original 3D render is minimized.Results: We demonstrate our approach with examples that are created by controlling the parameters of our sketch rendering algorithms.Conclusion: The examples not only show typical sketching artifacts that are common to human-drawn sketches but also demonstrate that it is capable of producing multiple sketching styles.     

Use of non-photorealistic rendering and photometric stereo in making bas-reliefs from photographs

Automatic bas-relief generation from 2D photographs potentially has applications to coinage, commemorative medals and souvenirs. However, current methods are not yet ready for real use in industry due to insufficient artistic effect, noticeable distortion, and unbalanced contrast. We previously proposed a shape-from-shading (SFS) based method to automatically generate bas-reliefs from single frontal photographs of human faces; however, suppression of unwanted details remained a problem. Here, we give experimental results showing how incorporating non-photorealistic rendering (NPR) into our previous framework enables us to both suppress unwanted detail, and yet also emphasize important features. We have consider an alternative approach to recovering relief shape, based on photometric stereo instead of SFS for surface orientation estimation. This can effectively reduce the computational time.     

Curvature-based stroke rendering

This paper describes an algorithm that renders lines that have various thicknesses and have sharp tapered ends. This algorithm does not require any special information on each local point of a line. The thickness is determined by curvature and lengths from both ends. Therefore the algorithm is applicable in a variety of line rendering situations, such as 3D rendering engines for high quality cel-animation-like effects, reuse of geometrical data designed by CAD for advertising purposes, edge enhancement in a photo retouching process with edge detection methods and so on. In addition, using the generated varying thicknesses, we have developed algorithms for shading and embossing effects.     

Automatically mimicking unique hand-drawn pencil lines

In applications such as architecture, early design sketches containing accurate line drawings often mislead the target audience. Approximate human-drawn sketches are typically accepted as a better way of demonstrating fundamental design concepts. To this end we have designed an algorithm that creates lines that perceptually resemble human-drawn lines. Our algorithm works directly with input point data and a physically based mathematical model of human arm movement. Our algorithm generates unique lines of arbitrary length given the end points of a line, without relying on a database of human-drawn lines. We found that an observational analysis obtained through various user studies of human lines made a bigger impact on the algorithm than a statistical analysis. Additional studies have shown that the algorithm produces lines that are perceptually indistinguishable from that of a hand-drawn straight pencil line. A further expansion to the system resulted in mimicked dashed lines.     

Perception-based animation rendering

In most currently produced computer generated animation there is significant visual information that is literally never seen because of the characteristics of the human visual system. By tailoring the rendering of animation images to match the characteristics of human visual perception, significant computational and image storage savings can be obtained while retaining perceived animation quality. Vision research indicates that the human visual system processes two information channels. The transient channel rapidly processes low spatial resolution full colour information. The sustained channel processes high spatial resolution luminance information at a much slower rate. This paper discusses how the rendering of animation images can be accomplished to match these perception characteristics and achieve significant savings while maintaining animation quality. Computation and storage savings of up to 80 per cent are possible. Several animation segments have been produced to demonstrate the viability of this approach.     

基于参考图像的色粉画模拟方法（CIDE 2013）

色粉画是一种极具表现力的绘画方式,本文提出一种基于参考图像色粉画效果模拟的非真实感绘制方法,其模拟过程分为铺底和细化二个阶段。在铺底阶段,利用mean-shift分割方法对参考图像进行分割获得区域和色调信息,并通过矢量场计算确定所得区域内笔画方向,在上述信息约束下通过对色粉画线画法以及侧面画法的模拟完成铺底工作;在细化阶段,针对参考图像所需突出的重要特征细节利用一致线条绘制方法获取,并通过色粉画点画法对其进行模拟。实验结果表明,通过上述二阶段模拟,本文所提方法能够快速高效的将参考图像转化为色粉画艺术化效果。     

基于OpenGL的快速图像渲染方法*

针对在动态图形绘制基础上进行图像渲染的问题,基于Mac OS X操作系统的核心制图与渲染技术,提出了重组OpenGL渲染流程实现加速图形绘制与图像渲染结合的管道化方法,目的是实现GPU完全承担绘图和渲染加速。整个流程无须CPU参与,在提高图形子系统性能的同时优化了应用程序响应能力。     

Interactive Control over Temporal Consistency while Stylizing Video Streams

Image stylization has seen significant advancement and widespread interest over the years, leading to the development of a multitude of techniques. Extending these stylization techniques, such as Neural Style Transfer (NST), to videos is often achieved by applying them on a per-frame basis. However, per-frame stylization usually lacks temporal consistency, expressed by undesirable flickering artifacts. Most of the existing approaches for enforcing temporal consistency suffer from one or more of the following drawbacks: They (1) are only suitable for a limited range of techniques, (2) do not support online processing as they require the complete video as input, (3) cannot provide consistency for the task of stylization, or (4) do not provide interactive consistency control. Domain-agnostic techniques for temporal consistency aim to eradicate flickering completely but typically disregard aesthetic aspects. For stylization tasks, however, consistency control is an essential requirement as a certain amount of flickering adds to the artistic look and feel. Moreover, making this control interactive is paramount from a usability perspective. To achieve the above requirements, we propose an approach that stylizes video streams in real-time at full HD resolutions while providing interactive consistency control. We develop a lite optical-flow network that operates at 80 Frames per second (FPS) on desktop systems with sufficient accuracy. Further, we employ an adaptive combination of local and global consistency features and enable interactive selection between them. Objective and subjective evaluations demonstrate that our method is superior to state-of-the-art video consistency approaches. maxreimann.github.io/stream-consistency     

基于纹理和草图的图像铅笔画绘制

针对目前铅笔画生成方法中的线条不够灵活、纹理缺少方向感的问题,提出了一种基于带方向的纹理和线条草图将一幅图像转换为铅笔画风格的方法。首先,对输入图像进行直方图匹配得到图像的色调图,并将图像分割为多个区域,对每个区域,根据其颜色和形状计算其色调和方向,以此决定铅笔纹理的色调和方向;然后,通过可调整的线性卷积方法得到铅笔画的线条草图;最后,将纹理和草图结合得到铅笔画效果。运用提出的方法对不同类型的自然图像进行了铅笔画的转换,并与已有的线卷积积分方法和基于色调的方法进行了对比。实验结果表明带方向的区域纹理能更好地模拟手工铅笔画纹理的方向,可调整的线条能够更好地模拟手工铅笔画的线条的随意性和灵活性。     

基于三维模型的风格化线条渲染方法

3D模型风格化线条绘制[1]中的一个最大问题是可见性的计算,当前在以复杂的模型计算线条可见性的算法中,不是交互式渲染速度太慢就是渲染后的动画不连贯,由此提出一种在GPU下快速、高质量地计算线条可见性的算法,其利用先进的可编程图形流水线技术,可以支持线条可见性和广泛的风格化选项.实验结果表明,该算法运算速度能够满足交互系统的实时性需求.     

图像和视频油画风格化研究

图像和视频的油画风格化是计算机图形学中非真实感绘制的热点问题之一,在动漫、娱乐等领域有着较广泛的应用。回顾了图像和视频油画风格化绘制的发展过程,分类介绍了各种方法的特点,并比较了不同方法的优缺点。在此基础上,讨论了图像和视频油画风格化绘制存在的难点和可能的研究方向。     

Optimizing subpixel rendering using a perceptual metric

Abstract— ClearType is a subpixel‐rendering method designed to improve the perceived quality of text. The method renders text at subpixel resolution and then applies a one‐dimensional symmetric mean‐preserving filter to reduce color artifacts. This paper describes a computational method and experimental tests to assess user preferences for different filter parameters. The computational method uses a physical display simulation and a perceptual metric that includes a model of human spatial and chromatic sensitivity. The method predicts experimentally measured preferences for filters for a range of characters, fonts, and displays.     

Non-photorealistic, depth-based image editing

Recent works in image editing are opening up new possibilities to manipulate and enhance input images. Within this context, we leverage well-known characteristics of human perception along with a simple depth approximation algorithm to generate non-photorealistic renditions that would be difficult to achieve with existing methods. Once a perceptually plausible depth map is obtained from the input image, we show how simple algorithms yield powerful new depictions of such an image. Additionally, we show how artistic manipulation of depth maps can be used to create novel non-photorealistic versions, for which we provide the user with an intuitive interface. Our real-time implementation on graphics hardware allows the user to efficiently explore artistic possibilities for each image. We show results produced with six different styles proving the versatility of our approach, and validate our assumptions and simplifications by means of a user study.     

应用遗传算法仿真墨扩散轮廓

墨扩散效果的模拟是水墨画仿真的重要工作之一,在分析绘画材料特性和扩散形成机制的基础上,提出一个全新的基于遗传算法的墨扩散仿真模型系统.首先将笔迹和纸张离散化为笔元和纸元;其次借用遗传算法基本概念和原理,对给定的输入笔迹进行轮廓提取作为初始种群,通过种群个体间的选择、重组和变异等遗传活动模拟笔元的扩散过程;最后为了更好地模拟墨扩散方向,使用Ashikhmin算法合成各种宣纸的自然纹理,增强了真实感.实验结果表明,方法可以生成丰富的扩散效果,并且接近真实水墨画.