3D Surface Texture Synthesis Based on Wavelet Transform

Real-world surface textures commonly consist of a spatial variation of reflectance properties combined with rough surface geometry, called 3D surface texture. Variation of illumination can produce dramatic changes their appearance. While previous work on super resolution pays great attention to 2D images, this paper proposes an inexpensive method for super resolution on 3D surface textures. First, four images under different illumination angles are captured for each sample surface texture, from which the surface gradient maps and the albedo map are extracted by Photometric Stereo. Then the surface gradient and albedo maps and three selected original images, which represent 3D surface texture, are processed by a modified 2D Example-based super resolution method to generate result representation sets with higher resolution. Finally, relight surface representations to generate high resolution texture images under any different illumination conditions. Experimental results show that this method provides more fine details compared to interpolation techniques.

This paper introduces an improved graph cut approach and combines it with commonly used surface texture representations for synthesis. Unlike graph cut which supports iterative refinement for improvement of the patch seams, the improved graph cut method re-synthesis the max error overlap region using k-nearest neighbor method. This paper follows a simple 3D surface texture synthesis framework, which comprises three steps: capture, synthesis and relighting. Firstly, it represents 3D surface textures under varied illumination directions using gradient and albedo maps. Then, it uses the surface representation to synthesis a description of a larger surface. Finally, it renders the surface representation. It proposes an improved graph cut method for the synthesis step, and the proposed method can generate perceptually smooth images of 3D surface texture from small samples.

Collecting pavement texture information is crucial to understand the characteristics of a road surface and to have essential data to support road maintenance. Traditional texture assessment techniques often require expensive equipment and complex operations. To ensure cost sustainability and reduce traffic closure times, this study proposes a rapid, cost-effective, and non-invasive surface texture assessment technique. This technology consists of capturing a set of images of a road surface with a mobile phone; then, the images are used to reconstruct the 3D surface with photogrammetric processing and derive the roughness parameters to assess the pavement texture. The results indicate that pavement images taken by a mobile phone can reconstruct the 3D surface and extract texture features with accuracy, meeting the requirements of a time-effective documentation. To validate the effectiveness of this technique, the surface structure of the pavement was analyzed in situ using a 3D structured light projection scanner and rigorous photogrammetry with a high-end reflex camera. The results demonstrated that increasing the point cloud density can enhance the detail level of the real surface 3D representation, but it leads to variations in road surface roughness parameters. Therefore, appropriate density should be chosen when performing three-dimensional reconstruction using mobile phone images. Mobile phone photogrammetry technology performs well in detecting shallow road surface textures but has certain limitations in capturing deeper textures. The texture parameters and the Abbott curve obtained using all three methods are comparable and fall within the same range of acceptability. This finding demonstrates the feasibility of using a mobile phone for pavement texture assessments with appropriate settings.

A sensor is proposed with interesting characteristics for applications such as autonomous navigation and virtual reality. The system extracts both 3D shape and surface texture. It is based on the projection of a regular pattern, observed by a single camera. It is cheap, requiring only a slide projector and a camera. Shape and intensity are extracted from one and the same image, thereby avoiding shape/texture alignment problems. Furthermore, the system is easy to use and calibrate. Because both the shape and the intensity information is obtained from a single image, the system can be used in dynamic environments, allowing robots to navigate during data acquisition or graphics designers to model moving objects for animation and virtual reality purposes. The system combines advantages of passive and active range acquisition.

We present a wavelet‐based approach for selecting patches in patch‐based texture synthesis. We randomly select the first block that satisfies a minimum error criterion, computed from the wavelet coefficients (using 1D or 2D wavelets) for the overlapping region. We show that our wavelet‐based approach improves texture synthesis for samples where previous work fails, mainly textures with prominent aligned features. Also, it generates similar quality textures when compared against texture synthesis using feature maps with the advantage that our proposed method uses implicit edge information (since it is embedded in the wavelet coefficients) whereas feature maps rely explicitly on edge features. In previous work, the best patches are selected among all possible using a L2 norm on the RGB or grayscale pixel values of boundary zones. The L2 metric provides the raw pixel‐to‐pixel difference, disregarding relevant image structures — such as edges — that are relevant in the human visual system and therefore on synthesis of new textures.

Seamless montage for texturing 3D models is very important in 3D video games and computer animations. The goal is to generate an arbitrarily large texture from a small sample image while both the sample texture and the result texture must be perceived by human observers to be the same and there is no obvious seam. This is slightly different from texture synthesis whose main principle is that the result texture must be non-periodical. Since there exist substantial periodical textures in real world, this paper presents a method for seamless montage without seams to form periodical textures. First we apply a quilting algorithm together with Wang Tiles to design the tile for montage, and we make comparison between them in terms of practical maneuverability. Then we employ the tile designed through Wang Tiles for seamless montage to generate a large texture with an arbitrary size. We also consider the montage of 3D surface textures under various illumination directions.

Vibration-assisted micro milling is a promising technique for fabricating engineered mi-cro-scaled surface textures. This paper presents a novel approach for theoretical modeling of three-dimensional (3D) surface textures produced by vibration-assisted micro milling. The proposed model considers the effects of tool edge geometry, minimum uncut chip thickness (MUCT), and material elastic recovery. The surface texture formation under different machining parameters is simulated and analyzed through mathematical modeling. Two typical surface morphologies can be generated: wave-type and fish scale-type textures, depending on the phase difference between tool paths. A 2-degrees-of-freedom (2-DOF) vibration stage is also developed to provide vibration along the feed and cross-feed directions during micro-milling process. Micro-milling experiments on copper were carried out to verify the ability to fabricate controlled surface textures using the vibration stage. The simulated and experimentally generated surfaces show good agreement in geometry and dimensions. This work provides an accurate analytical model for vibration-assisted micro-milling surface generation and demonstrates its feasibility for efficient, flexible texturing.

Many natural and man-made surface patterns are created by interactions between texture elements and surface geometry. We believe that the best way to create such patterns is to synthesize a texture directly on the surface of the model. Given a texture sample in the form of an image, we create a similar texture over an irregular mesh hierarchy that has been placed on a given surface.Our method draws upon texture synthesis methods that use image pyramids, and we use a mesh hierarchy to serve in place of such pyramids. First, we create a hierarchy of points from low to high density over a given surface, and we connect these points to form a hierarchy of meshes. Next, the user specifies a vector field over the surface that indicates the orientation of the texture. The mesh vertices on the surface are then sorted in such a way that visiting the points in order will follow the vector field and will sweep across the surface from one end to the other. Each point is then visited in turn to determine its color. The color of a particular point is found by examining the color of neighboring points and finding the best match to a similar pixel neighborhood in the given texture sample. The color assignment is done in a coarse-to-fine manner using the mesh hierarchy. A texture created this way fits the surface naturally and seamlessly.

Surface Texture for Geospatial Imaging Printed Product Using 3D Printer Technology

This paper presents an empirical study to investigate the use of photometric stereo (PS) for micro-scale 3D measurement of paper samples. PS estimates per-pixel surface orientation from images of a surface captured from the same viewpoint but under different illumination directions. Specifically, we investigate the surface properties of paper to test whether they are sufficiently well approximated by a Lambertian reflectance model to allow veridical surface reconstruction under PS and explore the range of conditions for which this model is valid. We present an empirical setup that is used to conduct a series of experiments in order to analyse the applicability of PS at the micro-scale. In addition, we determine the best 4, 6, and 8 light source tilt (illumination) angles with respect to multi-source micro-scale PS. Furthermore, an intensity based image registration method is used to test the accuracy of the recovery of surface normals. The results demonstrate that at the micro-scale: (a) Lambert model represents well the data sets with low root mean square (RMS) error between the original and reconstructed image, (b) increasing the light sources from 4 to 8 reduces RMS error, and (c) PS can be used to extract veridical surface normals.

For the measurement of areal surface texture, a non-contact measurement method for areal surface texture based on the co-integration of optical microscopy image measurement and white light microscopy interference measurement is proposed, which measures not only 2D size of length but also 3D surface texture. Based on this method, a 2D&3D optical microscopy measurement system for areal surface texture has been developed. It consists of compound optical microscopy imaging system, 3D precision displacement system, hardware circuit, and corresponding software. The practicality and effectiveness of the proposed method of measurement have been verified by the measurement results.

In this chapter, the algorithms to reconstruct the shape of the visible 3D surface using only the brightness variation information (shading, that is, the level variations of gray or colored) observed in the image are described. The inverse problem of reconstructing the shape of the visible surface from the changes in brightness in the image is known as the Shape from Shading (SfS) problem. The reconstruction of the visible surface should not be strictly understood as a 3D reconstruction of the surface. In fact, from a single point of the observation of a scene, a monocular vision system cannot estimate a distance measure between the observer and a visible object, so with the SfS algorithms there is a nonmetric but qualitative reconstruction of the 3D surface. The theory of the SfS is described, which is based on the knowledge of the light source (direction and distribution), the model of reflectance of the scene, the observation point, and the geometry of the visible surface, which together contributes to the image formation process. The relationships between the light intensity values of the image and the geometry of the visible surface are derived (in terms of the orientation of the surface, point by point) under some lighting conditions and the reflectance model. Other 3D surface reconstruction algorithms based on the Shape from XXX paradigm are also described, where XXX can be texture, structured light projected onto the surface to be reconstructed, or 2D images of the focused or defocused surface.

Hydrogenated amorphous silicon (a-Si:H) thin films have been considered for use in solar cell applications because of their significantly reduced cost compared to crystalline bulk silicon, however, their overall efficiency and stability are less than that of their bulk crystalline counterparts. Limited work has been performed on simultaneously solving the efficiency and stability issues of a-Si:H. Surface texturing and crystallization on a-Si:H thin film can be achieved through a one-step laser processing, which can potentially alleviate the disadvantages of a-Si:H in solar cell applications. In this study, hydrogenated and dehydrogenated amorphous silicon thin films deposited on glass substrates were irradiated by KrF excimer laser pulses and the effect of hydrogen on surface morphologies and microstructures are discussed. The sharp micrometer spikes are only fabricated on a-Si:H surfaces, and the large-grained and fine-grained regions caused by two crystallization processes are also induced by hydrogen. Enhanced light absorptance is observed due to light trapping based on surface geometry changes of a-Si:H films, while the formation of a mixture of nanocrystalline silicon and remained a-Si:H after crystallization suggests that the overall material stability can potentially be increased. The relationship between crystallinity, fluence and number of pulses is also investigated. Furthermore, a step-by-step crystallization process is introduced to protect the hydrogen diffusing out in order to reduce the defect density, and the relationship between residue hydrogen concentration, fluence and step width is discussed. Finally, the combined effects show that the one-step process of surface texturing and step-by-step crystallization induced by excimer laser processing is very promising for a-Si:H thin film solar cell applications.Hydrogenated amorphous silicon (a-Si:H) thin films have been considered for use in solar cell applications because of their significantly reduced cost compared to crystalline bulk silicon, however, their overall efficiency and stability are less than that of their bulk crystalline counterparts. Limited work has been performed on simultaneously solving the efficiency and stability issues of a-Si:H. Surface texturing and crystallization on a-Si:H thin film can be achieved through a one-step laser processing, which can potentially alleviate the disadvantages of a-Si:H in solar cell applications. In this study, hydrogenated and dehydrogenated amorphous silicon thin films deposited on glass substrates were irradiated by KrF excimer laser pulses and the effect of hydrogen on surface morphologies and microstructures are discussed. The sharp micrometer spikes are only fabricated on a-Si:H surfaces, and the large-grained and fine-grained regions caused by two crystallization processes are also induced by hydrogen....

Chapter 1 Photometric Stereo: An Overview

This paper models a texture as a 2D mapping onto a nonlinear manifold representing the local structures of the image. This manifold is learned from the set of local patches from an exemplar texture. A multiscale decomposition of this manifold valued representation is computed that mimics the orthogonal wavelet transform. The key ingredient of this decomposition is a geometric association field that drives the computations along the manifold. Iterated predictions leads to the computation of details coefficients over the features manifold. The resulting transform is invertible, non-linear and represents efficiently the local geometric structures of the exemplar. The multiscale coefficients of this transform are used to perform analysis and synthesis of textures.