A novel three-dimensional (3-D) photorealistic texturing process is presented that applies a view-planning and view-sequencing algorithm to the 3-D coarse model to determine a set of best viewing angles for capturing the individual real-world objects/building's images. The best sequence of views will generate sets of visible edges in each view to serve as a guide for camera field shots by either manual adjustment or equipment alignment. The best view tries to cover as many objects/building surfaces as possible in one shot. This will lead to a smaller total number of shots taken for a complete model reconstruction requiring texturing with photo-realistic effects. The direct linear transformation method (DLT) is used for reprojection of 3-D model vertices onto a two-dimensional (2-D) images plane for actual texture mapping. Given this method, the actual camera orientations do not have to be unique and can be set arbitrarily without heavy and expensive positioning equipment. We also present results of a study on the texture-mapping precision as a function of the level of visible mesh subdivision. In addition, the control points selection for the DLT method used for reprojection of 3-D model vertices onto 2-D textured images is also investigated for its effects on mapping precision. By using DLT and perspective projection theories on a coarse model feature points, this technique will allow accurate 3-D texture mapping of refined model meshes of real-world buildings. The novel integration flow of this research not only greatly reduces the human labor and intensive equipment requirements of traditional methods, but also generates a more appealing photo-realistic appearance of reconstructed models, which is useful in many multimedia applications.
A billiard ball tracking system is designed to combine with a visual guide interface to instruct users for a reliable strike. The integrated system runs on a PC platform. The system makes use of a vision system for cue ball, object ball and cue stick tracking. A least-squares error calibration process correlates the real-world and the virtual-world pool ball coordinates for a precise guidance line calculation. Users are able to adjust the cue stick on the pool table according to a visual guidance line instruction displayed on a PC monitor. The ideal visual guidance line extended from the cue ball is calculated based on a collision motion analysis. In addition to calculating the ideal visual guide, the factors influencing selection of the best shot among different object balls and pockets are explored. It is found that a tolerance angle around the ideal line for the object ball to roll into a pocket determines the difficulty of a strike. This angle depends in turn on the distance from the pocket to the object, the distance from the object to the cue ball, and the angle between these two vectors. Simulation results for tolerance angles as a function of these quantities are given. A selected object ball was tested extensively with respect to various geometrical parameters with and without using our integrated system. Players with different proficiency levels were selected for the experiment. The results indicate that all players benefit from our proposed visual guidance system in enhancing their skills, while low-skill players show the maximum enhancement in skill with the help of our system. All exhibit enhanced maximum and average hit-in rates. Experimental results on hit-in rates have shown a pattern consistent with that of the analysis. The hit-in rate is thus tightly connected with the analyzed tolerance angles for sinking object balls into a target pocket. These results prove the efficiency of our system, and the analysis results can be used to attain an efficient game-playing strategy.
KEYWORDS: Inspection, Error analysis, Optical engineering, Manufacturing, 3D modeling, 3D vision, Computer science, Information science, 3D metrology, 3D applications
While the uniform sampling method is quite popular for pointwise measurement of manufactured parts, we present three novel sampling 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 surface subdivision process that applies two different approaches. One uses the direct triangular patch subdivision while the other uses the indirect sectional adaptive approach. The direct adaptive sampling approach can distribute points more closely around edges, corners, and vertices as found on the class of machined products. The indirect adaptive 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 geometric description using a small number of sampling points. Beyond the practical application value of a technique to inspect curved surface objects, this kind of technique is also of value in understanding the principle of optimum sampling in a 3D sense. The local adjustment sampling strategy 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 predefined 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 adaptive sampling using triangular patches, are moved the shortest distance to edges and corners for global optimum approximation, again showing this method's superiority. (Partial Abstract)
Optimizing view planning achieves the goal of minimum occlusion and minimum rotation to insure complete inspection of an object, and not only satisfies the goal of view planning, but also automatically maximizes the number of surfaces to which adaptive sampling can most fully be applied. The best view based on visible edge length can usually not only minimize the number of rotations needed to inspect an entire object, but can also provide the maximum amount of information for integration with nonuniform sampling techniques for a variety of parts and manufacturing processes. This new integration approach of first viewing then sampling establishes that the optimization criterion of maximum edge length is more robust than anticipated in its original role for view planning alone. The best view based on the number of visible faces and the face area has proven applicable to integrating the finite element (FEM) centroid sampling and indirect adaptive sampling techniques, respectively, for the inspection of sculptured surface products. Experimental work has verified various theories proposed. The verified view planning criteria include both the edge length and the number of visible faces criterion. Of them, the number of visible faces criterion not only maximizes the number of visible meshes for centroid sampling, but also reveals the maximum amount of high curvature regions of an object.
KEYWORDS: 3D modeling, Solid modeling, Process modeling, Reconstruction algorithms, Computer aided design, 3D image processing, Clouds, Photogrammetry, LIDAR, Data modeling
Two efficient workflow are developed for the reconstruction of a 3D full color building model. One uses a point wise sensing device to sample an unknown object densely and attach color textures from a digital camera separately. The other uses an image based approach to reconstruct the model with color texture automatically attached.
The point wise sensing device reconstructs the CAD model using a modified best view algorithm that collects the maximum number of construction faces in one view. The partial views of the point clouds data are then glued together using a common face between two consecutive views. Typical overlapping mesh removal and coarsening
procedures are adapted to generate a unified 3D mesh shell structure. A post processing step is then taken to combine the digital image content from a separate camera with the 3D mesh shell surfaces. An indirect uv mapping procedure first divide the model faces into groups within which every face share the same normal direction. The corresponding images of these faces in a group is then adjusted using the uv map as a guidance. The final assembled image is then glued back to the 3D mesh to present a full colored building model. The result is a virtual building that can reflect the true dimension and surface material conditions of a real world campus building. The image based modeling procedure uses a commercial photogrammetry package to reconstruct the 3D model. A novel view planning algorithm is developed to guide the photos taking procedure. This algorithm successfully generate a minimum set of view angles. The set of pictures taken at these view angles can guarantee that each model face shows up at least in two of the pictures set and no more than three. The 3D model can then be reconstructed with minimum amount of labor spent in correlating picture pairs. The finished model is compared with the original object in both the topological and dimensional aspects. All the test cases show exact same topology and reasonably low dimension error ratio. Again proving the applicability of the algorithm.
KEYWORDS: Inspection, Manufacturing, 3D modeling, Finite element methods, Machine vision, Composites, Computing systems, Computer simulations, 3D vision, 3D applications
Indirect adaptive sampling techniques are introduced specifically for 3D inspection of sculptured surfaces (free form) normally found on objects produced by extrusion, die casting, and molding processes. The techniques successfully extends optimum 2D sampling methods to 3D applications. The modified 2-D adaptive sampling techniques are used sequentially twice. First, the critical cross sections are optimally selected, then each section is itself optimally sampled to develop an accurate description using a small number of sampling points. Optimizing view planning achieves the goal of minimum occlusion and minimum rotation to insure complete inspection of an object, and not only satisfies the goal of view planning, but also automatically maximizes the number of surfaces to which adaptive sampling can most fully be applied. The best view based on the number of visible faces and the face area has proven applicable to integrating the finite element (FEM) centroid sampling and indirect adaptive sampling techniques respectively, for the inspection of sculptured surface products. Experimental work has verified that the best view based on the number of visible faces not only maximizes the number of visible meshes for centroid sampling, but also reveals the maximum amount of high curvature regions of an object.
KEYWORDS: Inspection, Finite element methods, Manufacturing, Error analysis, Solids, Chemical elements, Statistical modeling, 3D modeling, Computing systems, 3D metrology
While the uniform sampling method is quite popular for pointwise measurement of manufactured parts, this paper proposes three novel sampling strategies which emphasize 3D non-uniform inspection capability. They are: (a) the adaptive sampling, (b) the local adjustment sampling, and (c) the finite element centroid sampling techniques. The adaptive sampling strategy is based on a recursive surface subdivision process. Two different approaches are described for this adaptive sampling strategy. One uses triangle patches while the other uses rectangle patches. Several real world objects were tested using these two algorithms. Preliminary results show that sample points are distributed more closely around edges, corners, and vertices as desired for many classes of objects. Adaptive sampling using triangle patches is shown to generally perform better than both uniform and adaptive sampling using rectangle patches. The local adjustment sampling strategy 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. In a hybrid approach, uniform points sets and non-uniform points sets, first preprocessed by the adaptive sampling algorithm on a real world object were then tested using the local adjustment sampling method. The results show that the initial point sets when preprocessed by adaptive sampling using triangle patches, are moved the least amount of distance by the subsequently applied local adjustment method, again showing the superiority of this method. The finite element sampling technique samples the centroids of the surface triangle meshes produced from the finite element method. The performance of this algorithm was compared to that of the adaptive sampling using triangular patches. The adaptive sampling with triangular patches was once again shown to be better on different classes of objects.
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