基于复用计算的大纹理实时合成

文中提出一种基于复用计算的纹理合成方法,逐步地利用已合成的部分纹理来生成更大的纹理块,以进行后续的纹理合成计算.由此,该方法可节省大量耗时的纹理块选择及缝合计算,提高了合成效率.实验表明,新方法可实时合成2048×2048像素的大纹理,而已有工作至多只能以交互的速度进行这样的合成.     

基于PSO的Wang Tiles纹理合成

如何在纹理样图中选择组成Wang Tiles的图像块决定着纹理的合成质量。基于PSO的Wang Tiles纹理合成通过粒子群优化算法在纹理样图中快速搜索边界差异最小的图像块,并用选取的图像块构建Wang Tiles,最后用Wang Tiles纹理合成算法合成纹理。实验表明,该算法合成的纹理具有较少的接缝,比随机选择图像块具有更好的合成效果。     

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.     

Accelerated Parallel Texture Optimization

Texture optimization is a texture synthesis method that can efficiently reproduce various features of exemplar textures. However, its slow synthesis speed limits its usage in many interactive or real time applications. In this paper, we propose a parallel texture optimization algorithm to run on GPUs. In our algorithm, k-coherence search and principle component analysis （PCA） are used for hardware acceleration, and two acceleration techniques are further developed to speed up our GPU-based texture optimization. With a reasonable precomputation cost, the online synthesis speed of our algorithm is 4000＋ times faster than that of the original texture optimization algorithm and thus our algorithm is capable of interactive applications. The advantages of the new scheme are demonstrated by applying it to interactive editing of flow-guided synthesis.     

Completion-based texture design using deformation

In this paper, we present a novel approach for designing a variety of large textures from a single small sample texture. Firstly, the original small texture is segmented into layers, each of which contains one particular texture element. Secondly, each layer is deformed using a set of chaotic-based transformation operations. Thirdly, all the deformed layers are added together to form a new texture, which is a natural variation of the original sample texture. Since each layer is deformed independently, adding the deformed layers together usually results in a texture with overlapping regions and holes. We employ the graphcut algorithm and an example-based image inpainting technique to seamlessly patch the overlapping regions and to fill the holes. Moreover, an optimized graphcut synthesis algorithm and a new cyclic texture synthesis technique are also developed for efficiently creating large seamless textures. As a result, our approach shows particular strength in generating a large variety of textures from a single sample texture while avoiding highly repetitive patterns. Our experiments demonstrate that the proposed technique can also be used for other texture synthesis applications, such as texture synthesis from multiple samples.     

基于泊松填充的纹理自适应插值方法

针对新图形技术条件下的纹理合成问题,提出一种纹理插值方法,可将源纹理图像自适应拉伸为不同尺寸的纹理图像并保持其清晰度不改变。首先,采用高维图像插值算法将源纹理裂变为目标纹理分辨率,作为中间过渡纹理;其次,利用自然图像的自相似性,依据中间纹理像素特征随机从源纹理中选取像素块;最后,使用泊松图像编辑算法将源纹理像素块平滑嵌入到中间纹理的间隙区域,得到最终的合成纹理。通过与现有算法的大量对比实验表明,该算法对静态和非静态纹理合成问题都能适用,且合成结果与源纹理具有较高的视觉一致性。另外,该算法逻辑简单、计算快速,无法复杂优化计算或者学习训练步骤,适合在低硬件配置的移动平台应用。     

Analysis and Controlled Synthesis of Inhomogeneous Textures

Many interesting real‐world textures are inhomogeneous and/or anisotropic. An inhomogeneous texture is one where various visual properties exhibit significant changes across the texture's spatial domain. Examples include perceptible changes in surface color, lighting, local texture pattern and/or its apparent scale, and weathering effects, which may vary abruptly, or in a continuous fashion. An anisotropic texture is one where the local patterns exhibit a preferred orientation, which also may vary across the spatial domain. While many example‐based texture synthesis methods can be highly effective when synthesizing uniform (stationary) isotropic textures, synthesizing highly non‐uniform textures, or ones with spatially varying orientation, is a considerably more challenging task, which so far has remained underexplored. In this paper, we propose a new method for automatic analysis and controlled synthesis of such textures. Given an input texture exemplar, our method generates a source guidance map comprising: (i) a scalar progression channel that attempts to capture the low frequency spatial changes in color, lighting, and local pattern combined, and (ii) a direction field that captures the local dominant orientation of the texture. Having augmented the texture exemplar with this guidance map, users can exercise better control over the synthesized result by providing easily specified target guidance maps, which are used to constrain the synthesis process.     

Interactive texture design and synthesis from mesh sketches

Geometry mesh introduces user control into texture synthesis and editing, and brings more variations in the synthesized results. But still two problems related remain in need of better solutions. One problem is generating the meshes with desired size and pattern efficiently from easier user inputs. The other problem is improving the quality of synthesized results with mesh information. We present a new two-step texture design and synthesis method that addresses these two problems. Besides example texture, a small piece of mesh sketch drawn by hand or detected from example texture is input to our algorithm. And then a mesh synthesis method of geometry space is provided to avoid optimizations cell by cell. Distance and orientation features are introduced to improve the quality of mesh rasterization. Results show that with our method, users can design and synthesize textures from mesh sketches easily and interactively.     

可控的连续多尺度纹理合成

针对同一幅合成图像的不同区域间,如何实现纹理图案的多尺度连续变化,提出一种基于像素的多尺度纹理合成算法。在逐像素点合成的基础上,通过为已知匹配点建立一个到连续的多分辨率样图的正向映射,并重新采样合成像素点,实现合成结果的任意尺度连续渐变的可控性。实验证明该方法不增加大量的处理时间,并可适用于大多数基于样图的逐点合成方法。     

应用PSO的快速纹理合成算法

应用PSO的快速纹理合成算法是一种高效的纹理合成算法,应用粒子群优化(PSO)算法对基于块采样的纹理合成算法的搜索匹配过程进行了改进,改变了原算法的全遍历搜索过程,在不影响合成质量的前提下加快了合成速度．本算法对于按序和随机的各种应用都能在一台中等的PC机上几秒内合成高质量的纹理．并对算法执行中的粒子数、迭代次数对合成速度和合成效果的影响进行了详细的分析．     

复用计算的虚拟肝脏体纹理合成与映射方法

虚拟手术中器官纹理能够给用户直观反映,加强临场感和操作感。研究在虚拟肝脏手术中纹理的表现技术,先合成体纹理空间,把二维情况下基于复用计算的纹理合成技术进行改进,扩展至三维空间中进行体纹理块分布并着色;同时计算每个三角面片内部点集并着色,以此增加纹理的真实感;切割肝脏体能看到内部纹理。实验结果表明,该方法能够生成具有高度真实感以及同样本体纹理相似的三维纹理,且合成速度能够满足虚拟手术要求。     

纹理合成的自相关性判别法及其应用

从加快纹理相似性的判别速度出发,提出了一种纹理合成的自相关性判别法.传统的纹理合成算法随着邻域和样本的增大,计算量将成倍增加,纹理合成速度减慢的劣势逐渐体现出来.因此,算法对样本纹理建立简单的自相关性距离查找表,利用L邻域内像素的自相关性距离作为像素匹配的判别依据,以查找取代传统匹配过程中的繁琐计算,极大地加快了合成速度,可实现动态的、多精度的合成效果调控,以及避免块匹配中易出现纹理接缝的问题.经验证,该算法可在纹理合成、图像修补及纹理检索中应用,并可很好地达到实时的应用要求.     

纹理的标准性和强标准性纹理的快速识别及合成

分析了纹理合成中时间开销最大的匹配过程,发现了对一类具有特征任意匹配性纹理,可以大大降低匹配精度甚至忽略匹配过程,从而加快纹理生成速度．通过对这类纹理特性的概括,引入了纹理标准性概念,利用可变尺度滑动窗口的灰度距离对标准性进行度量;并结合大量统计结果,给出纹理标准性区分标准,对强标准性纹理使用低精度的匹配或零搜索来合成纹理．实验结果证明,文中对于强标准性的纹理区分可靠有效,生成纹理的速度大大提高,且质量无明显降低．     

图像的纹理标准性度量及其应用

通过分析纹理合成中子块参数对合成速度及质量的影响,发现对于一类纹理图像,不依赖于参数的选择即可快速高效地进行纹理合成。选择子块灰度平均值作为度量指标,根据纹理标准性强的图像应具有的特征,提出了一种新的计算图像纹理标准性系数的算法。结合大量计算结果,界定了一般图像、强标准性纹理以及弱标准性纹理的分类标准。并将其应用到纹理合成当中,对强标准性纹理图像的合成采用大尺度子块及零搜索的合成方法,提高了合成速度的同时保持合成质量不变。     

Method of Direct Texture Synthesis on Arbitrary Surfaces

A direct texture synthesis method on arbitrary surfaces is proposed in this paper. The idea is to recursively map triangles on surface to texture space until the surface is completely mapped. First, the surface is simplified and a tangential vector field is created over the simplified mesh. Then, mapping process searches for the most optimal texture coordinates in texture sample for each triangle, and the textures of neighboring triangles are blended on the mesh. All synthesized texture triangles are compressed to an atlas. Finally, the simplified mesh is subdivided to approach the initial surface. The algorithm has several advantages over former methods: it synthesizes texture on surface without local parameterization; it does not need partitioning surface to patches; and it does not need a particular texture sample. The results demonstrate that the new algorithm is applicable to a wide variety of texture samples and any triangulated surfaces.     

基于结构的纹理合成

提出一个简单有效的基于样图的纹理合成新方法．现有纹理合成算法仅考虑两块待匹配块之间对应元素的颜色差别作为评价相似性的量度，对于一些纹理图象，找到的不一定是最相似的匹配块，因此合成后，没有得到令人满意的效果．为此，提出一个新的纹理合成算法，不仅考虑了两个匹配块之问的颜色相似性，还充分考虑了结构的差别，把结构的相似性作为匹配块之间相似性量度的重要因素之一．具体作法是：从样本图象产生一个基于结构的新的特征映射，降低结构上不连续的程度，从而获得比较理想的合成结果．     

基于条块拼接的快速纹理合成

针对离线纹理合成算法所生成纹理占用较多存储空间的问题,提出一种所生成纹理可紧凑保存的快速纹理合成算法.该算法相继沿垂直和水平方向以条块拼接的方式合成纹理,合成结果可表示为一系列切割路径的组合,仅需保存这些切割路径即可在渲染时实时重建出纹理图像.通过在预处理中计算得到一组误差小的平行切割路径,合成时无需进行匹配,使得合成速度大幅提高.该算法对于在水平和垂直方向具有自相似性的纹理具有较高的合成质量.     

Wei-Levoy纹理合成算法的搜索带加速方法

Wei和Levoy于2001年提出的纹理合成算法是当前典型的基于样图的纹理合成算法之一，但该方法存在算法实现复杂、使某些纹理的合成质量大大降低等缺点。文章提出了一种新的通过设置搜索带减小搜索范围的方法对Wei-Levoy纹理合成算法进行加速，并取得了理想的效果。     

基于GPU加速的保结构纹理合成

提出一种基于Chamfer距离的保结构纹理合成方法。使用Chamfer距离度量纹理结构特征的相似度,在查找匹配块的同时计算纹理在颜色空间和结构特征空间的匹配度,从而解决以往纹理合成中有显著结构特征的纹理容易出现不连续的问题。但是Chamfer距离的计算量很大,而且随着纹理合成图分辨率的提高,计算成本会变得相当高昂以至于难以负担。因此,提出了基于GPU加速的保结构纹理合成方法,通过并行查找匹配块提高合成效率。实验证明本方法既提高了结构纹理的合成质量,又使得保结构纹理方法的合成速度大大提高,且与纹理合成图的分辨率无关。     

The Promise and Perils of Near-Regular Texture

Motivated by the low structural fidelity for near-regular textures in current texture synthesis algorithms, we propose and implement an alternative texture synthesis method for near-regular texture. We view such textures as statistical departures from regular patterns and argue that a thorough understanding of their structures in terms of their translation symmetries can enhance existing methods of texture synthesis. We demonstrate the perils of texture synthesis for near-regular texture and the promise of faithfully preserving the regularity as well as the randomness in a near-regular texture sample.