基于3维模型的数字浮雕生成技术

目的 浮雕是雕塑艺术的一种,根据其空间结构和用途的不同分为高浮雕、浅浮雕和凹浮雕3类。随着数字化技术和3D打印技术的发展,数字化浮雕的生成技术已经成为近年来计算机图形学领域的研究热点之一,从3维模型生成浮雕以其真实自然的效果成为浮雕生成的主要方法之一。为了使即将进入该领域的学者尽快了解该方法的现状和发展趋势,本文对3种类型的浮雕生成技术进行了系统的综述。方法 介绍了3种类型的浮雕生成技术,着重比较分析了基于3维网格模型的数字浅浮雕生成过程中的关键技术,存在问题及解决方案。针对复杂3维网格模型在生成数字凹浮雕过程中存在的部分细节信息丢失、特征线类型体现形式不完善、线条与形体间的过渡尚未解决、生成浮雕效果不自然等具体问题,提出了适用于3维复杂网格模型生成数字凹浮雕的研究方案。同时,从角色动画序列出发,对最优浮雕的生成技术进行了探讨,探讨结合信息熵理论计算选择最佳动作及观察视角的场景,还原艺术家的创作过程,为适用于面向3维打印的用户浮雕产品定制服务提供了可行的解决方案。结果 基于3维模型的浮雕生成方法是生成数字浮雕的一种重要方法,如何通过压缩和细节保持相关算法得到效果自然的浮雕模型一直是研究者们研究的热点问题。结论 虽然由3维模型生成数字浮雕是一种行之有效的方法,但是仍存在细节信息丢失、线条过渡不自然、特征线类型不完善等几个值得继续研究的问题,另外一个值得研究的问题就是如何智能地从3维动画序列生成浮雕。     

A framework for digital sunken relief generation based on 3D geometric models

Sunken relief is a special art form of sculpture whereby the depicted shapes are sunk into a given surface. This is traditionally created by laboriously carving materials such as stone. Sunken reliefs often utilize the engraved lines or strokes to strengthen the impressions of a 3D presence and to highlight the features which otherwise are unrevealed. In other types of relief, smooth surfaces and their shadows convey such information in a coherent manner. Existing methods for relief generation are focused on forming a smooth surface with a shallow depth which provides the presence of 3D figures. Such methods unfortunately do not help the art form of sunken reliefs as they omit the presence of feature lines. We propose a framework to produce sunken reliefs from a known 3D geometry, which transforms the 3D objects into three layers of input to incorporate the contour lines seamlessly with the smooth surfaces. The three input layers take the advantages of the geometric information and the visual cues to assist the relief generation. We have modified the existing techniques of line drawings and relief generation, and then combine them organically for this particular purpose.     

Region-based bas-relief generation from a single image

Bas-relief is an art form part way between sculpture and drawing. In this paper, we present an algorithm for generating a bas-relief from a single image, inspired by the process that artists use to create reliefs. We do not aim to recover exact depth values for objects in the image, which is a tricky computer vision problem, requiring assumptions that are rarely satisfied. Instead, we determine layers based on relative depth ordering of objects (and their parts) in the image, and use this information to construct surfaces in the 3D relief model. Feature lines are extracted and used to build a new region-based representation of the input image. During surface construction, a base surface is first generated; it is then augmented using both intensity and gradient information from the original image. To prevent depth errors arising due to augmentation, a feedback process is used to refine the output. Our experimental results show the generated bas-reliefs have smooth boundaries with appropriate height relationships, a key property of bas-reliefs created by artists. We demonstrate that our algorithm works well for a range of input images, including human faces, flowers and animals.     

Inner engraving for the creation of a balanced LEGO sculpture

LEGO is a globally popular toy composed of colorful interlocking plastic bricks that can be assembled in many ways; however, this special feature makes designing a LEGO sculpture particularly challenging. Building a stable sculpture is not easy for a beginner; even an experienced user requires a good deal of time to build one. This paper provides a novel approach to creating a balanced LEGO sculpture for a 3D model in any pose, using centroid adjustment and inner engraving. First, the input 3D model is transformed into a voxel data structure. Next, the model’s centroid is adjusted to an appropriate position using inner engraving to ensure that the model stands stably. A model can stand stably without any struts when the center of mass is moved to the ideal position. Third, voxels are merged into layer-by-layer brick layout assembly instructions. Finally, users will be able to build a LEGO sculpture by following these instructions. The proposed method is demonstrated with a number of LEGO sculptures and the results of the physical experiments are presented.     

Preserving detailed features in digital bas-relief making

This paper presents a novel algorithm for digitally making bas-reliefs. The problem requires visibly retaining fine details present in original 3D objects while greatly compressing their depths to produce an almost planar result. Our approach performs compression on the gradient domain; gradients are first estimated from a height field representing the input scene. A new compression function based on arctangent is introduced to preserve desired details of reliefs, allowing accurate height adjustment via a data-dependent threshold. We explicitly consider how to preserve fine details present in the original objects, which is crucial for producing high-quality bas-reliefs. Laplacian coordinates are used to store detailed features before depth compression and then restore them afterwards. Laplacian sharpening is also used to emphasize detailed features in the relief itself. Prior to depth compression, we process the input height field to reduce gaps in height, and detect the outer silhouette which allows to compute the output relief relative to a planar background or other surface, by solving a Poisson equation. This combination of techniques allows our method to produce bas-reliefs with well-preserved details.     

一种面向并联机构的雕刻刀具系统设计

设计并实现了一种新的面向并联机构的雕刻刀具系统．整个系统主要集成了主轴—刀具子系统、工件平台及多传感器子系统、电气控制子系统等部分．通过所设计的刀具系统与并联机器人的有机结合,实现了汉字的雕刻及雕刻过程中力/力矩信息的实时监控,验证了其可行性和有效性．     

RTX 平台下实时全软件数控雕刻系统

计算机仿真设计与制造需要极高的实时性和可控性,由于Windows操作系统本身实时性的缺陷,给计算机仿真应用带来了一些不确定因素.经过充分论证,引入了IntervalZero公司的基于Windows的实时仿真解决方案RTX,并结合某型号数控雕刻机的设计要求,总结出了Windows环境下RTX实时仿真应用系统的设计方法及RTX环境下全软件数控雕刻系统主要功能模块程序编写,并将这种设计方法成功应用于某数控雕刻系统中.实际雕刻实例表明RTX平台下全软件程序能够满足数控雕刻系统对实时性要求.     

论中国画中的线条魅力

人类有相互沟通的语言方式,同样人与艺术也拥有相应的沟通媒介,中国画艺术的艺术表达媒介便是画中线条,中国画中的线条不仅是艺术表达的方式更是整个艺术作品的灵魂。在古代名画中的线条绘制过程极其灵活,之所以被很多艺术名家所采用就是因为在灵活多变的前提之下的线条魅力能够吸引众人的眼球,向读者传达丰富的艺术内涵。文章就中国画中的线条进行深度解析。     

Efficient and Dynamic Simplification of Line Drawings

In this paper we present a pipeline for rendering dynamic 2D/3D line drawings efficiently. Our main goal is to create efficient static renditions and coherent animations of line drawings in a setting where lines can be added, deleted and arbitrarily transformed on‐the‐fly. Such a dynamic setting enables us to handle interactively sketched 2D line data, as well as arbitrarily transformed 3D line data in a unified manner. We evaluate the proximity of screen projected strokes to simplify them while preserving their continuity. We achieve this by using a special data structure that facilitates efficient proximity calculations in a dynamic setting. This on‐the‐fly proximity evaluation also facilitates generation of appropriate visibility cues to mitigate depth ambiguities and visual clutter for 3D line data. As we perform all these operations using only line data, we can create line drawings from 3D models without any surface information. We demonstrate the effectiveness and applicability of our approach by showing several examples with initial line representations obtained from a variety of sources: 2D and 3D hand‐drawn sketches and 3D salient geometry lines obtained from 3D surface representations.     

试论城市雕塑设计中的民族性与文化性

雕塑是立体艺术中的一个种类,城市雕塑又是伴随城市格局的兴起而产生的现代艺术创作类型,可以说城市雕塑是能够在某种程度上体现城市文化的公共艺术作品。作者以民族性和文化性为切入点,通过探讨其如何在城市雕塑设计中具体体现来揭示其对于提升现代城市雕塑设计内涵所起到的重要作用,同时也讨论了以民族性和文化性为特色的城市雕塑设计未来的发展思路。     

DTI in Context: Illustrating Brain Fiber Tracts In Situ

We present an interactive illustrative visualization method inspired by traditional pen‐and‐ink illustration styles. Specifically, we explore how to provide context around DTI fiber tracts in the form of surfaces of the brain, the skull, or other objects such as tumors. These contextual surfaces are derived from either segmentation data or generated using interactive iso‐surface extraction and are rendered with a flexible, slice‐based hatching technique, controlled with ambient occlusion. This technique allows us to produce a consistent and frame‐coherent appearance with precise control over the lines. In addition, we provide context through cutting planes onto which we render gray matter with stippling. Together, our methods not only facilitate the interactive exploration and illustration of brain fibers within their anatomical context but also allow us to produce high‐quality images for print reproduction. We provide evidence for the success of our approach with an informal evaluation with domain experts.     

Geometry and construction of straight lines in log-polar images

This paper investigates, how straight lines are mapped to the non-Euclidean log-polar image plane and how their properties in log-polar coordinates can be used to perform two fundamental measurement operations: the construction of straight lines of given orientation angle and the measurement of distances along these lines. It is shown, how the two operations can be efficiently implemented for discrete log-polar images. The usefulness of the developed theory is demonstrated by applying it to different image processing tasks. As a first example, it is used for line and circle detection in log-polar sampled images. As a second example, it is used to construct epipolar lines and perform disparity estimation in log-polar images. Experiments with both synthetic and real images are presented, and the feature detection results are quantitatively evaluated.     

Computer‐assisted Relief Modelling: A Comprehensive Survey

As an art form between drawing and sculpture, relief has been widely used in a variety of media for signs, narratives, decorations and other purposes. Traditional relief creation relies on both professional skills and artistic expertise, which is extremely time‐consuming. Recently, automatic or semi‐automatic relief modelling from a 3D object or a 2D image has been a subject of interest in computer graphics. Various methods have been proposed to generate reliefs with few user interactions or minor human efforts, while preserving or enhancing the appearance of the input. This survey provides a comprehensive review of the advances in computer‐assisted relief modelling during the past decade. First, we provide an overview of relief types and their art characteristics. Then, we introduce the key techniques of object‐space methods and image‐space methods respectively. Advantages and limitations of each category are discussed in details. We conclude the report by discussing directions for possible future research.     

基于OpenGL的数控雕刻机加工仿真系统的研究

本文介绍了一种基于OpenGL的数控雕刻机加工仿真系统.它的实现采用了Visual C＋＋6.0开发工具,以及用OpenGL开发的雕刻机三维加工仿真软件.本文还重点介绍了刀具加工轨迹的建模及三维动画的实现.     

基于套色浮雕的动漫素材创作技术

浮雕是雕塑与绘画相结合的产物。艺术家可以在平面上雕刻出具有三维观感的作品,并华丽地贴附在墙面或器皿的表面,因此它十分普及地用于建筑设计或用具装帧中。该项目瞄准这一历史久远、表现能力很强的艺术形式,将它用于动漫形象的创作。在二维图像平面上通过独立设计的自适应色彩融合和图像投影算法,将常规数码图像改造成为视觉上具有高低层次...     

Hairy Slices II: Depth Cues for Visualizing 3D Streamlines Through Cutting Planes

Visualizing 3D vector fields is challenging because of occlusion problems and the difficulty of providing depth cues that adequately support the perception of direction of flow lines in 3D space. One of the depth cues that has proven most valuable for the perception of other kinds of 3D data, notably 3D networks and 3D point clouds, is structure-from-motion (also called the Kinetic Depth Effect); another powerful depth cue is stereoscopic viewing. We carried out an experiment of the perception of direction for short streamlines passing through a cutting plane. The conditions included viewing with and without structure-from-motion and with and without stereoscopic depth. Conditions also include comparing streamtubes to lines. The results show that for this particular task, stereo provided an effective depth cue, but structure-from-motion did not. Ringed streamtubes and streamcones provided good 3D direction information, even without stereoscopic viewing. We conclude with guidelines for viewing slices through vector fields.     

基于平面不封闭图形切割的路径规划

在平面切割环节中，如何确定更短切割路径以减少加工成本、降低设备损耗和提升切割质量是工业应用和学术研究的重点。目前国内外对平面切割路径的研究主要集中于封闭图形，为此，针对在激光刀模行业中不封闭图形的问题，提出一种基于禁忌搜索的贪婪算法和贪婪准则的局部优化。首先使用构建型的贪婪算法和改进型的禁忌搜索算法相结合的方式对加工过程中的图元路径进行优化排序，随后提出贪婪准则的局部优化系数，削弱贪婪算法的“贪心”思想，解决加工路径的规划和优化问题。实验数据表明，禁忌搜索的贪婪算法和局部优化在对切割路径的规划和空行程优化上有显著效果，空行程减少50%以上，并且其优化性能和图元数量成正比，能有效地解决刀模行业以及其他激光雕刻行业中图形不封闭的切割难题。     

Differential geometry properties of lines of curvature of parametric surfaces and their visualization

We present algorithms for computing the differential geometry properties of lines of curvature of parametric surfaces. We derive a unit tangent vector, curvature vector, binormal vector, torsion, and algorithms to evaluate their higher-order derivatives of lines of curvature of parametric surfaces. Among these quantities, it is shown that the curvature and its first derivative of the lines of curvature lend a hand for the formation of curved plates in shipbuilding. We also visualize the twist of lines of curvature, which enables us to observe how much the osculating plane of the line of curvature turns about the tangent vector.     

A Knowledge-Aided Line Network Oriented Vectorisation Method for Engineering Drawings

Vectorisation is the foundation in recognising engineering components from paper form drawings. Due to the complexity of problems and the difficulty of techniques, the vectorisation method relying merely on the image itself cannot get satisfactory results. It is now widely agreed that the knowledge must be applied more or less to aid the vectorisation. The capability of the vectorisation method itself should also be thus improved. This paper analyses the problems of existing vectorisation methods, introduces the complete concept of global vectorisation, and proposes a whole new line network oriented global vectorisation method. This method uses global information to vectorise a line in one step, and carries out the global vectorisation of line networks. Therefore, the problem of separating one line is solved, and a complex analysis of crossings is avoided. The performance of vectorisation is improved clearly. Furthermore, it can vectorise lines in any orientations well, and can vectorise a dashed line in one step. Aided by the related knowledge, local details of vectorisation are refined. A performance evaluation compared with other vectorisation methods is also included.     

High Reliefs from 3D Scenes

We present a method for synthesizing high reliefs, a sculpting technique that attaches 3D objects onto a 2D surface within a limited depth range. The main challenges are the preservation of distinct scene parts by preserving depth discontinuities, the fine details of the shape, and the overall continuity of the scene. Bas relief depth compression methods such as gradient compression and depth range compression are not applicable for high relief production. Instead, our method is based on differential coordinates to bring scene elements to the relief plane while preserving depth discontinuities and surface details of the scene. We select a user‐defined number of attenuation points within the scene, attenuate these points towards the relief plane and recompute the positions of all scene elements by preserving the differential coordinates. Finally, if the desired depth range is not achieved we apply a range compression. High relief synthesis is semi‐automatic and can be controlled by user‐defined parameters to adjust the depth range, as well as the placement of the scene elements with respect to the relief plane.