三维离散点采样表面基于全局优化的纹理合成算法

提出了一个直接在三维离散点采样表面上进行基于全局优化的纹理合成算法．算法首先对点模型表面进行基于协方差分析的递归式聚类削分，然后通过对各初始聚类进行优化调整和区域生长，得到更为均匀的计算单元块且使相邻单元块间具有重叠区域．基于所得到的计算单元块和样本纹理，在点模型表面上建立了一个全局的纹理合成能量方程，并采用最大期卑值算法迭代优化求解出一个全局的能量最小值．在全局优化算法中，通过加入的约束条件，进而给出了点模型颜色纹理的修复算法和流引导的可控纹理合成算法．由于点模型表面离散点元的稠密性，通过对离散点元的法向基于纹理合成结果进行相应的扰动，进一步增强了表面纹理的几何粗糙感．实验结果表明，该文的算法在点采样几何表面上有效地保持了生成的纹理结构和视觉效果的连续性和平滑性，得到了令人满意的结果。     

Detail-generating geometry completion for point-sampled geometry

In this paper, we present a novel method for detail-generating geometry completion over point-sampled geometry. The main idea consists of converting the context-based geometry completion into the detail-based texture completion on the surface. According to the influence region of boundary points surrounding a hole, a smooth patch covering the hole is first constructed using radial base functions. By applying region-growing clustering to the patch, the patching units for further completion with geometry details is then produced, and using the trilateral filtering operator formulated by us, the geometry-detail texture of each sample point on the input geometry is determined. The geometry details on the smooth completed patch are finally generated by optimizing a constrained global texture energy function on the point-sampled surfaces. Experimental results demonstrate that the method can achieve efficient completed patches that not only conform with their boundaries, but also contain the plausible 3D surface details.     

Geometry Texture Synthesis Based on Laplacian Texture Image

In this paper, we present a new method to synthesize geometric texture details on an arbitrary surface from a sample texture patch. The key idea is to use Laplacian texture images to represent geometric texture details, which in turn facilitate simple and effective geometry texture synthesis and enable flexible geometry texture editing. Given a sample model and a target model, we first select a patch from the sample model and extract the geometric texture details. Next, we construct a Laplacian texture imag...     

快速结构化图像修补

图像修补的目的是对图像中缺失的区域进行修复,或是将图像中的物体抠去并进行背景填充,以取得融合到难以用肉眼分辨的效果。在图像修补的过程中,较大的结构信息是修补的难点。为此提出了一种快速结构化的图像修补算法,该方法将图像修补分为结构修补与纹理填充两个部分,即在用户指定待修补区域与结构曲线之后,首先定义全局最优化能量函数,并用动态规划与置信度传播的算法将其最小化来完成结构修补;然后对剩余的待修补区域通过按行扫描来进行纹理填充,其中对于边界处的点是使用基于样本的修补算法,而对于待修补区域内部的点,则使用快速的加权Ashikhmin-WL算法,扫描完成后输出修补后的图像;最后实现了一个快速结构化图像修补系统,并给出一些实验结果,从实验结果中可以看到,该方法的修补流程与算法是有实际应用价值的。     

Seamless Montage for Texturing Models

We present an automatic method to recover high‐resolution texture over an object by mapping detailed photographs onto its surface. Such high‐resolution detail often reveals inaccuracies in geometry and registration, as well as lighting variations and surface reflections. Simple image projection results in visible seams on the surface. We minimize such seams using a global optimization that assigns compatible texture to adjacent triangles. The key idea is to search not only combinatorially over the source images, but also over a set of local image transformations that compensate for geometric misalignment. This broad search space is traversed using a discrete labeling algorithm, aided by a coarse‐to‐fine strategy. Our approach significantly improves resilience to acquisition errors, thereby allowing simple and easy creation of textured models for use in computer graphics.     

点模型的多分辨率形状编辑

提出了一种基于几何细节映射的点模型的形状编辑方法.几何细节是曲面的一个重要属性,定义几何细节为原始曲面及其基曲面之间的向量差,该基曲面由多层次B样条所构成.通过基曲面上的局部仿射坐标,则可以得到与之对应的多分辨率几何细节表示,曲面的低频信息和高频信息易被用户所指定的频段分离.通过调节基曲面的形状,再将这些几何细节映射上去,可以对模型进行保细节的变形;如果将几何细节映射到其他物体上,将可以得到几何细节迁移的结果.为点模型开发了多种特征保持的编辑算子,实验结果表明,所提出的方法是一种有效的点模型造型算法.     

Surface completion for shape and appearance

In this paper, we present a new surface content completion system that can effectively repair both shape and appearance from scanned, incomplete point set inputs. First, geometric holes can be robustly identified from noisy and defective data sets without the need for any normal or orientation information. The geometry and texture information of the holes can then be determined either automatically from the models’ context, or interactively from users’ selection. We use local parameterizations to align patches in order to extract their curvature-driven digital signature. After identifying the patch that most resembles each hole region, the geometry and texture information can be completed by warping the candidate region and gluing it onto the hole area. The displacement vector field for the exact alignment process is computed by solving a Poisson equation with boundary conditions. Our experiments show that the unified framework, founded upon the techniques of deformable models, local parameterization, and PDE modeling, can provide a robust and elegant solution for content completion of defective, complex point surfaces.     

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.     

Synthesis and rendering of bidirectional texture functions on arbitrary surfaces

The bidirectional texture function (BTF) is a 6D function that describes the appearance of a real-world surface as a function of lighting and viewing directions. The BTF can model the fine-scale shadows, occlusions, and specularities caused by surface mesostructures. In this paper, we present algorithms for efficient synthesis of BTFs on arbitrary surfaces and for hardware-accelerated rendering. For both synthesis and rendering, a main challenge is handling the large amount of data in a BTF sample. To addresses this challenge, we approximate the BTF sample by a small number of 4D point appearance functions (PAFs) multiplied by 2D geometry maps. The geometry maps and PAFs lead to efficient synthesis and fast rendering of BTFs on arbitrary surfaces. For synthesis, a surface BTF can be generated by applying a texton-based sysnthesis algorithm to a small set of 2D geometry maps while leaving the companion 4D PAFs untouched. As for rendering, a surface BTF synthesized using geometry maps is well-suited for leveraging the programmable vertex and pixel shaders on the graphics hardware. We present a real-time BTF rendering algorithm that runs at the speed of about 30 frames/second on a mid-level PC with an ATI Radeon 8500 graphics card. We demonstrate the effectiveness of our synthesis and rendering algorithms using both real and synthetic BTF samples.     

Geometric texture modeling

Texture mapping has become an essential tool in any synthetic rendering scheme that aims at photorealism. Texture mapping typically associates any point on the surface of the rendered object with a location in the texture space. The surface point is then assigned rendering attributes, such as color or translucency from the respective location found in the texture space. Texture mapping techniques have also been used in attempts to emulate highly detailed geometry on the surfaces of objects. The proposed surface detail synthesis approach closes the loop from modeling to rendering using computer graphics texture mapping techniques, bringing them back into the geometric modeling phase. This article focuses primarily on texturing techniques that relate to shape modeling and surface geometry alteration.     

带约束的基于样图地表纹理合成技术研究

在传统的视景仿真开发过程中,研究人员需要将海量的航空影像照片经过数字化等一系列处理变成可使用的地表纹理,映射在地形表面,生成地景数据库.此法耗费大量人力,而且地景库一经生成就不可再改变,真实性降低.提出一种新的地表纹理的生成方法,以随机生成的高度信息作为约束,不同的地表纹理单元作为样图,采用带约束的基于样图纹理合成算法合成出真实地表纹理图像.实验中,通过改变高程约束和对多种地表纹理进行组合,可以方便快速地合成高质量的二维地表纹理图像.提出的纹理合成的方法,为今后与数字地图相结合开发地景数据库,积累一定的经验.对提高视景数据库的真实性具有实际意义.     

Image inpainting with salient structure completion and texture propagation

Image inpainting technique uses structural and textural information to repair or fill missing regions of a picture. Inspired by human visual characteristics, we introduce a new image inpainting approach which includes salient structure completion and texture propagation. In the salient structure completion step, incomplete salient structures are detected using wavelet transform, and completion order is determined through color texture and curvature features around the incomplete salient structures. Afterwards, curve fitting and extension are used to complete the incomplete salient structures. In the texture propagation step, the proposed approach first synthesizes texture information of completed salient structures. Then, the texture information is propagated into the remaining missing regions. A number of examples on real and synthetic images demonstrate the effectiveness of our algorithm in removing occluding objects. Our results compare favorably to those obtained by existing greedy inpainting techniques.     

Perspective-aware texture analysis and synthesis

This paper presents a novel texture synthesis scheme for anisotropic 2D textures based on perspective feature analysis and energy optimization. Given an example texture, the synthesis process starts with analyzing the texel (TEXture ELement) scale variations to obtain the perspective map (scale map). Feature mask and simple user-assisted scale extraction operations including slant and tilt angles assignment and scale value editing are applied. The scale map represents the global variations of the texel scales in the sample texture. Then, we extend 2D texture optimization techniques to synthesize these kinds of perspectively featured textures. The non-parametric texture optimization approach is integrated with histogram matching, which forces the global statics of the texel scale variations of the synthesized texture to match those of the example. We also demonstrate that our method is well-suited for image completion of a perspectively featured texture region in a digital photo.     

Geometric texturing using level sets

We present techniques for warping and blending (or subtracting) geometric textures onto surfaces represented by high resolution level sets. The geometric texture itself can be represented either explicitly as a polygonal mesh or implicitly as a level set. Unlike previous approaches, we can produce topologically connected surfaces with smooth blending and low distortion. Specifically, we offer two different solutions to the problem of adding fine-scale geometric detail to surfaces. Both solutions assume a level set representation of the base surface which is easily achieved by means of a mesh-to-level-set scan conversion. To facilitate our mapping, we parameterize the embedding space of the base level set surface using fast particle advection. We can then warp explicit texture meshes onto this surface at nearly interactive speeds or blend level set representations of the texture to produce high-quality surfaces with smooth transitions.     

不规则块的图像补全算法

目的 目前在图像补全领域研究的重点和难点是补全具有复杂结构信息和丰富纹理信息的大破损区域的图像。传统的基于样本块的图像补全算法主要采用规则的模板块和匹配块来进行补全,补全过程中不能充分利用图像的结构或纹理的不规则信息,从而影响算法修复的精度和效率。针对这一问题,本研究提出一种基于不规则块的图像补全算法。方法 在该算法中,首先利用结构稀疏度来区分图像的结构信息和纹理信息并基于结构稀疏度和置信度计算破损区域边界点的优先级,然后选择优先级最高的点构造规则模板块。对处于复杂结构区域的模板块,如果其邻域含有已知的结构信息,则膨胀该规则模板并利用其周围的结构信息来辅助构造不规则模板块。接下来,在图像完好区域内搜索与该模板块对应的匹配块,如果该匹配块的邻域包含有效的结构信息,则膨胀该匹配块并补充其周围的结构信息来完善该不规则匹配块。最后,利用该不规则匹配块补全破损区域。对于补全过程中块间接缝造成的视觉不连通问题,本研究利用图像的纹理信息来进行修饰。结果 将本文算法与4种修复效果较好的算法（3种基于规则块的算法和1种基于局部敏感哈希的修复算法）进行对比,通过8组经典图像进行实例验证,采用客观评价指标峰值信噪比PSNR和主观视觉连通性进行评价,结果表明本文提出的算法峰值信噪比相较4种对比算法均有04 dB的提高,且在补全的精细度和视觉连通性方面有更佳的效果。结论 本文算法在补全含有较复杂结构和丰富纹理的破损自然图像、壁画图像和目标物体移除上有较好的修复效果,普适性较强。     

Geometry synthesis on surfaces using field-guided shape grammars

We show how to model geometric patterns on surfaces. We build on the concept of shape grammars to allow the grammars to be guided by a vector or tensor field. Our approach affords greater artistic freedom in design and enables the use of grammars to create patterns on manifold surfaces. We show several application examples in visualization, anisotropic tiling of mosaics, and geometry synthesis on surfaces. In contrast to previous work, we can create patterns that adapt to the underlying surface rather than distorting the geometry with a texture parameterization. Additionally, we are the first to model patterns with a global structure thanks to the ability to derive field-guided shape grammars on surfaces.     

在点模型上实现三维纹理合成的算法

为了避免网格重建过程而直接在三维点采样表面上进行纹理合成,研究了在点模型上的三维纹理合成的算法。利用KDtree这种数据结构在离散采样点上构建点与点的邻域关系,通过投影和建立匹配窗得到每一个待合成纹理的点与样图的映射关系,根据映射关系在样图中找出与待定点纹理值最佳匹配的点。最后将该匹配点的纹理值赋给待定点,同时结合邻域关系实现多点同时赋值。实验结果表明,该算法能有效地保持了生成的纹理结构和视觉效果的连续性和平滑性,具有耗时短、灵活可控、较好的鲁棒性等特点。     

结合图像细节特征的全局优化纹理合成

提出了一种结合图像细节特征的全局优化纹理合成算法.作者利用非线性分解方法获取纹理细节作为特征图,将其作为纹理图像一个新的信息通道来引导纹理合成.联合图像细节信息通道和颜色通道,在图像上建立了一个全局的纹理合成能量方程,采用最大期望值算法迭代优化求解出一个全局的能量最小值.在全局优化算法中,构建样本纹理和待合成纹理之间的各个信息通道直方图匹配算法,进一步提高纹理合成的质量.文中同时给出了结合细节特征的图像和视频纹理合成算法,实验结果表明,文中的方法较好地解决了纹理合成中合成的纹理图像结构不连续或特征结构容易断裂等问题.     

Texture Synthesis From Photographs

The goal of texture synthesis is to generate an arbitrarily large high‐quality texture from a small input sample. Generally, it is assumed that the input image is given as a flat, square piece of texture, thus it has to be carefully prepared from a picture taken under ideal conditions. Instead we would like to extract the input texture from any surface from within an arbitrary photograph. This introduces several challenges: Only parts of the photograph are covered with the texture of interest, perspective and scene geometry introduce distortions, and the texture is non‐uniformly sampled during the capture process. This breaks many of the assumptions used for synthesis. In this paper we combine a simple novel user interface with a generic per‐pixel synthesis algorithm to achieve high‐quality synthesis from a photograph. Our interface lets the user locally describe the geometry supporting the textures by combining rational Bézier patches. These are particularly well suited to describe curved surfaces under projection. Further, we extend per‐pixel synthesis to account for arbitrary texture sparsity and distortion, both in the input image and in the synthesis output. Applications range from synthesizing textures directly from photographs to high‐quality texture completion.