Papers by Keyword: Perspective Projection

Abstract: The reasonable distribution of the video monitoring points in the substation is one of the technical problems to be solved in the engineering. We combined the camera calibration algorithm with the real application of the substation video monitoring point layout, and proposed a nonlinear camera calibration method of the external parameters based on the 3D real scene, which is suited for the substation video surveillance system. The optimal video monitoring points are determined by the relationship between the video produced by the camera movement and the visual scope displayed with the 3D real scene, and testified by the location of each object through its boundary geometric element shown in the pictures. It has been proved applicable by the video simulating analysis on the 110kV main transformer monitoring points. This method has been used in the engineering design of the Guangdong Power Grid substation video surveillance system.

Abstract: Shape from shading (SFS) is a classical and important problem in the domain of computer vision. The first paper of the authors gives a new image irradiance equation for perspective SFS method to reconstruct the hybrid surfaces that have both diffuse reflection and specular reflection. This paper presents a new approach to compute the viscosity solution of the resulting Hamilton- Jacobi (H-J) equation considering the boundary conditions. The approach is based on 2D central Hamiltonian and iterative sweeping method. Experiments are performed on three images and the results show the effectiveness of the proposed approach.

Abstract: Shape from shading (SFS) is a classical and important problem in the domain of computer vision. This paper presents a new image irradiance equation for perspective SFS method to reconstruct the hybrid surfaces that have both diffuse reflection and specular reflection. The hybrid reflectance model composed of a linear combination of Oren-Nayar model and Ward model is used to express the hybrid surfaces. An imaging model incorporating near point light source, perspective camera projection and the hybrid reflectance model is established. Under this model, the image irradiance equation has been derived as a non-linear partial differential equation (PDE). The resulting PDE is associated with a static Hamilton-Jacobi (H-J) equation considering the boundary conditions. Thus, the image irradiance equation of hybrid surfaces can be solved further.

Abstract: Pose estimation of 3d object is a hot research in the field of computer vision. This paper presents a novel pose estimation method based on colored markers. To overcome the effect of the luminance and other colors, this method uses the HSV color space and isolates the colors operating only on chromaticity plane where value (V) has no actual effect for identifying the colored regions of interest. The template is then applied on the remaining colors in order to find the center of the region. The pixels which have the same color but are not in the marker area are excluded, since they are considered noisy. The template guarantees the stability and efficiency of the extraction of the feature points. Compared with the CDT algorithm, the proposed method can extract reliable center points, and has higher accuracy in pose estimation for planar rigid objects. At last, experimental results demonstrate the efficiency of the method.

Abstract: Since traditional pose estimation methods with the features of points, lines and so on might not be applied directly to round-shape workpieces, a new pose estimation method for round-shape workpieces genetic algorithm based was proposed. Compared with previous studies, this method needs no auxiliary information, such as points, lines, concentric circles and so on. Firstly, transformation model of perspective projection of round-shape workpiece was created, and the round-shape workpiece was characterized by analytic equation. Secondly, via detecting the contour and extracting its feature of workpiece, a feature error function was established with respect to the pose angles, which was a multi-objective nonlinear function. Finally, the error function was solved by an improved genetic algorithm and the pose estimation of round-shape workpiece was achieved. The result of related experiments showed that the method had high accuracy, and to some extent inhibited the effects of noise.

Abstract: The article presents an approach to the three-dimensional reconstruction of vertebral column based on shape matching. Technique is established on the basis of marching cubes algorithm, through the rotated transformation and perspective projection toward every 3D model of vertebration, the projection drawing which is similar to the corresponding vertebration in the computed tomography is formed. Then, through the matching of the projection drawing and the corresponding vertebration in the CT, we can obtain the experimental result by adjust rotation parameters according to the matching outcome. The last step is to record the rotation parameters α, β and the translation parameters h, v, and by justifying the according parameter of the vertebration model in the standard vertebral column model based upon the circumgyrate of every vertebra and the translation parameters, the post-model of vertebration is reconstructed by means of visualization technology. The experimental result turned out that the reconstructed 3D model has a commendable matching attribute and meticulous accuracy compared with the real spinal column. Even the quality of the experimental CT is not so satisfied, the technique can still process match and reestablish the exact model column.

Abstract: Quaternion sandwiching formula to compute perspective projections has been given by Ron Goldman in an article titled “Understanding quaternions”. In this paper, we applied this method to obtain perspective images of 3D objects, and proposed a modified method to interpolate two projection planes with different directions and distances from eye point to acquire an intermediate viewing plane. Experimental results show that our interpolation method improves the disadvantage of uneven movement speed when quaternion SLERP method is directly adopted.

Abstract: Geometrical calibration is one of the key technologies for multi-channel projection system. In consideration of the complexity and cost of existing correction methods which need camera to collect the feedback images, another algorithm was proposed to correct geometrical distortion. Firstly, the pixels of the uncorrected image were mapped to the cylindrical screen with equal-arc length method. Then the correction of the geometrical distortion was realized by transforming the pixels on the cylindrical screen to the 2D coordinate of pre-corrected image according to perspective projection. Combined with simplified edge blending method, this system completed the high-angle-of-attack flight simulation based on two-channel projection and could be a platform for high-angle-of-attack flight test and flight accident reconstruction.

Abstract: Virtual surface measurement is necessary to assist the actual measurement of large deployable space antenna structure. To realize a virtual surface measurement on this kind of structures, we take several steps to get the virtual measurement images. A virtual 3D model of the antenna structure and virtual hung system are constructed; virtual measure rules, coded marks and uncoded marks are also built up. The pinhole camera model is used to simulate the actual photogrammetric measurement tools. Through examples with OpenCV tools, the virtual measurement method is verified to be reasonable. Then different resolution images of perspective projections of the virtual measurement in virtual camera positions and orientations are obtained. Proper selections of the camera resolution and proper positions and orientations of the camera are found through virtual measurement experiments. Such results can be used in an actual photogrammetric measurement. The virtual measurement method can be used to reduce the attempt times and to assist the actual measurement with available photogrammetric measurement tools.

Abstract: The article describes a patented method of displaying objects that secures natural visual perception of the objects displayed without distortions in their scaling relation and the dimensional depth. The author considers a group of linear perspectives with homographic function to display/map 3D visual scenes. The article also describes matrices for projective transformation.