Surface Of Real Objects Research Articles

Non-uniform surface sampling techniques for three-dimensional object inspection

While the uniform sampling method is quite popular for point- wise measurement of manufactured parts, we present three novel sam- pling strategies that emphasize 3D non-uniform inspection capability. They are direct and indirect adaptive sampling and local adjustment sampling. The adaptive sampling strategy is based on a recursive sur- face subdivision process that applies two different approaches. One uses the direct triangular patch subdivision while the other uses the in- direct sectional adaptive approach. The direct adaptive sampling ap- proach can distribute points more closely around edges, corners, and vertices as found on the class of machined products. The indirect adap- tive sampling techniques extend optimum 2D sampling methods to 3D applications. The modified 2D adaptive sampling techniques are used sequentially twice; first, the critical cross sections are optimally selected, and then each section is optimally sampled to develop an accurate geo- metric description using a small number of sampling points. Beyond the practical application value of a technique to inspect curved surface ob- jects, this kind of technique is also of value in understanding the principle of optimum sampling in a 3D sense. The local adjustment sampling strat- egy uses a set of predefined starting points and then finds the local optimum position of each nodal point. This method approximates the object by moving the points toward object edges and corners. The pre- defined starting points sets include uniform and non-uniform sampling distribution generated by the direct adaptive sampling approach. The results show that the initial point sets, when preprocessed by the adap- tive sampling using triangular patches, are moved the shortest distance to edges and corners for global optimum approximation, again showing this method's superiority. The performance comparisons of applying uni- form sampling and adaptive sampling are made based on the MSE mean square error value between the real object surfaces and their approximating surfaces. The adaptive sampling methods exhibit better performance than the uniform sampling methods in reducing the MSE values with fewer sample points. In addition to the performance advan- tage over uniform sampling, the non-uniform sampling techniques we propose also proved to be integratable with view planning for the inspec- tion of products by different manufacturing processes. © 2008 Society of

Tangible Interfaces for Interactive Multimedia Presentations

This article is devoted to tangible interfaces for steering and control of interactive multimedia presentations. Various methods for digital encoding of physical objects are considered and their applicability in surface encoding for tangible interface components is discussed. Experiments with presentation controls, based on direct interaction with digitally encoded printed handouts are reported. An innovative approach for transferring presentation controls from printed handouts to surfaces of real physical objects is introduced. Consequently labels, digitally enhanced with CLUSPI codes are created and presentation control trials involving real products with digitally encoded surfaces are conducted. USB and wireless cameras are employed as CLUSPI readers for implementing surface based interactions and a portable communication device with an embedded camera is considered as a possible truly mobile solution.

Surface detail in computer models

Quantitative characterization of surface appearance is an important but difficult task. Surfaces of real world objects are detailed landscapes, with complex geometry and local optical properties. Surface appearance is strongly affected by the direction from which it is viewed and illuminated. Computational modeling of surface texture has potential uses in many applications including realistic rendering for computer graphics and robust recognition for computer vision. For recognition, the overall structure of the object is important, but fine-scale details can assist the recognition problem greatly. We develop models of surface texture and demonstrate their use in recognition tasks. We also describe a texture camera for capturing fine-scale surface details. Specifically, the texture camera measures reflectance and surface height variation using curved mirrors. We discuss why measurements and models of fine scale detail are important in modern industrial applications.

ItkQuadEdgeMesh: A Discrete Orientable 2-Manifold Data Structure for Image Processing

There is nowadays an increasing need in interaction between discrete surfaces (2-manifolds) and images. More specifically, segmentation and registration of n-dimensional images are taking advantage of a priori geometrical information, most often provided as discrete 2-manifolds. Most of the publicly available libraries are oriented either toward mesh processing or image processing. Through a careful study we will show that none of those libraries are complete enough to fullfill image, surface and joint image-surface interaction. We propose to implement in ITK library a powerful 2-manifold data structure. The choice of ITK was driven by the fact that it provides the best base framework along with a strong n-dimensional image kernel. Based on a Quad-Edge data structure, it has been specifically tailored not only to represent orientable 2-manifolds (surfaces of real objects) but also ease further processing. We illustrate the integration of the design into ITK as a native object, enhancing existing algorithms. We also illustrate the power of the new design for further surface processing.

Calibration Free Virtual Display System Using Video Projector onto Real Object Surface

In this paper, we propose a novel virtual display system for a real object surface by using a video projector, so that the viewer can feel as if digital images are printed on the real surface with arbitrary shape. This system consists of an uncalibrated camera and video projector connected to a same PC and creates a virtual object by rendering 2D contents preserved beforehand onto a white object in a real world via a projector. For geometry registration between the rendered image and the object surface correctly, we regard the object surface as a set of a number of small rectangular regions and perform geometry registration by calculating homographies between the projector image plane and the each divided regions. By using such a homography-based method, we can avoid calibration of a camera and a projector that is necessary in a conventional method. In this system, we perform following two processes. First of all, we acquire the status of the object surface from images which capture the scene that color-coded checker patterns are projected on it and generate image rendered on it without distortion by calculating homographies. After once the projection image is generated, the rendered image can be updated if the object surface moves, or refined when it is stationary by observing the object surface. By this second process, the system always offers more accurate display. In implementation, we demonstrate our system in various conditions. This system enables it to project them as if it is printed on a real paper surface of a book. By using this system, we expect the realization of a virtual museum or other industrial application.

Multilevel representation and transmission of real objects with progressive octree particles

We present a multilevel representation scheme adapted to storage, progressive transmission, and rendering of dense data sampled on the surface of real objects. Geometry and object attributes, such as color and normal, are encoded in terms of surface particles associated to a hierarchical space partitioning based on an octree. Appropriate ordering of surface particles results in a compact multilevel representation without increasing the size of the uniresolution model corresponding to the highest level of detail. This compact representation can progressively be decoded by the viewer and transformed by a fast direct triangulation technique into a sequence of triangle meshes with increasing levels of detail. The representation requires approximately 5 bits per particle (2.5 bits per triangle) to encode the basic geometrical structure. The vertex positions can then be refined by means of additional precision bits, resulting in 5 to 9 bits per triangle for representing a 12-bit quantized geometry. The proposed representation scheme is demonstrated with the surface data of various real objects.

Investigation of Surface Characteristic Effects on Real-Virtual Object Alignment in Stereoscopic Augmented Reality Images

This paper reports a virtual pointer alignment experiment carried out in a stereoscopic augmented reality environment, in which the known conflict between binocular fusion and object interposition cues is expected to play a major role. The object was to evaluate subjects' perceptual sensitivity to target position at designated probe points on a cylindrical real object surface, visual texture of that surface, virtual pointer geometrical properties, and degree of binocular disparity. The results confirmed the primary findings from previous experiments: that both surface texture and target position have significant influences. Subjective evaluation of form of the virtual pointer revealed that the three dimensional pointer was preferred over the one and two-dimensional pointers.

Modeling Wave Set: Definition and Application of a New Topological Organization for 3D Object Modeling

In this paper we deal with the problem of constructing geometric models from 3D data points from the surface of real objects. The model generated by our system handles a complete mesh of the object surface obtained by deformation of an initial mesh. Basic topologies, such as three or six connectivity, provide a local and poor characterization in the representation mesh. Therefore, we have introduced a new topological organization called modeling wave set (MWS) where an n-connectivity relationship is established. With the MWS, an object is simultaneously modeled in n subspaces of features, corresponding to n different viewing directions of the object. The use of MWS allows for new solutions to typical computer vision problems, such as recognition and positioning, to be found. Our paper shows this topology and the way it has been tested in detail. Partial modeling based on MWS is a promising research line along which we have started to work and to obtain satisfactory results.

Effect of Surface Characteristics on Alignment of Graphic and Real Objects in a Stereoscopic Augmented Reality Environment

A virtual pointer (VP) alignment task at designated probe points on a cylinder real object surface was carried out in a stereoscopic augmented reality environment. The object was to evaluate subjects' sensitivity to surface texture, target position on the curved surface, VP orientation relative to the surface, and binocular disparity. The main findings were: a) surface texture had a significant effect, with highly textured surfaces facilitating less error than low textured surfaces; b) target position had a significant influence, with the central position relative to the observer being better for locating surface positions than the off-centre position. Results are discussed in terms of hypothesised visual perceptual interactions.

Design of a Tactile Display Based on Human Characteristics of Visual and Tactile Sensory Fusion.

In general, there is no good hardware of tactile display for tele-robot and virtual reality, because to present the curvature of the curved surface with continuous values is too difficult. On the other hand, in the psychophysical studies, human visual and tactile sensations have illusory fusion characteristics. Namely, the human sensory quantity on size, position and orientation of object is different from the real quantity. Therefore, we can recognize curved surface of real objects through visual and tactile sensations, even if exact tactile information is not presented. Furthermore the visual information is realize easily by computer graphical technology. So, by utilizing human characteristics of sensory illusory fusion, realization of the tactile display can be simplified. In this study, human characteristics of visual and tactile sensory fusion are measured by psychological experiments and a tactile display is designed based on the results of the experiments. In the designed tactile display, only some curved patterns are utilized of instead of presenting many curved surface patterns. Namely, using the human sensory fusion characteristics on visual and tactile sensory fusion, the tactile display can be simplified.

Vibratory tactile display of image-based textures

Virtual worlds must integrate tactile and force sensations to create a sense of presence. Our tactile display conveys the textural sensation of object surfaces to a user's fingertip. This vibratory tactile display contains a contact pin array that transmits vibrations to the human skin. This type of device has been investigated as a reading aid for the blind since the 1960s. A device called the Optacon, developed by J.G. Linvill and J.C. Bliss (1966) was intended for use by a visually impaired person. Therefore, methods for representing texture have not been discussed extensively for that device. We present techniques for virtually replicating surface texture sensations through a vibratory tactile display, using image data of objects. M. Minsky et al. (1990) demonstrated a method for presenting surface textures by force display, including-if needed-visual images of textures. Their system generated the images from geometrical shapes of depth maps. In contrast, we use pictures of real object surfaces to provide the distribution data for tactile stimulus.

Determination of displacement of hole profile in cylindrical shells subjected to torsion using holographic interferometry

Experimental methods in the mechanics of deformable solids have made a substantial contribution to those analyses of stress in the deformed state of shells widely applied in various areas of machine manufacture and construction [3]. Holographic interferometry has become important for contactless determination of the displacement field on the surfaces of real objects and is characterized by a sensitivity on the order of the wavelength of light [2]. The potential for using this method to study deformation of the hole profile in cylindrical shells subjected to stretching forces and internal pressure has been researched in [4, 5]. However, this approach, which requires recording of three Fresnel holograms and interpretation of a double-exposure interferogram with respect to the absolute fringe, is extremely complicated to apply and can be accomplished only in a holographic system that is vibration-free. In addition, a number of stringent conditions must be observed for determining first-order interference (the first-order fringe).