204 research outputs found
Fast and Accurate Camera Covariance Computation for Large 3D Reconstruction
Estimating uncertainty of camera parameters computed in Structure from Motion
(SfM) is an important tool for evaluating the quality of the reconstruction and
guiding the reconstruction process. Yet, the quality of the estimated
parameters of large reconstructions has been rarely evaluated due to the
computational challenges. We present a new algorithm which employs the sparsity
of the uncertainty propagation and speeds the computation up about ten times
\wrt previous approaches. Our computation is accurate and does not use any
approximations. We can compute uncertainties of thousands of cameras in tens of
seconds on a standard PC. We also demonstrate that our approach can be
effectively used for reconstructions of any size by applying it to smaller
sub-reconstructions.Comment: ECCV 201
A computationally efficient method for handâeye calibration
Purpose: Surgical robots with cooperative control and semiautonomous features have shown increasing clinical potential, particularly for repetitive tasks under imaging and vision guidance. Effective performance of an autonomous task requires accurate handâeye calibration so that the transformation between the robot coordinate frame and the camera coordinates is well defined. In practice, due to changes in surgical instruments, online handâeye calibration must be performed regularly. In order to ensure seamless execution of the surgical procedure without affecting the normal surgical workflow, it is important to derive fast and efficient handâeye calibration methods. Methods: We present a computationally efficient iterative method for handâeye calibration. In this method, dual quaternion is introduced to represent the rigid transformation, and a two-step iterative method is proposed to recover the real and dual parts of the dual quaternion simultaneously, and thus the estimation of rotation and translation of the transformation. Results: The proposed method was applied to determine the rigid transformation between the stereo laparoscope and the robot manipulator. Promising experimental and simulation results have shown significant convergence speed improvement to 3 iterations from larger than 30 with regard to standard optimization method, which illustrates the effectiveness and efficiency of the proposed method
Recent Advances in Graph Partitioning
We survey recent trends in practical algorithms for balanced graph
partitioning together with applications and future research directions
Volunteer Engagement in Housing Co-Operatives â Civil Society âen miniatureâ
Housing coâoperatives host miniature versions of civil society. They vitalise a social system that is shaped by formal regulations, economic functions, and a population of private housing units. The study examines factors that influence a personâs willingness to volunteer in civic society using a multilevel analysis based on survey data from 32 coâoperatives and 1263 members. To do so, the social exchange theory is extended to include the member value approach, which connects social engagement with the fulfillment of a range of needs, thus going beyond a narrow economic cost benefit analysis. Study results show that volunteer engagement largely depends on the degree to which members can expect to experience their own achievement. This finding provides an explanation for significant differences in the engagement levels beyond factors that have already been determined (age, level of education). On an organizational level, the study reveals that the age of an organization influences volunteer engagement, but that the size and the degree of professionalization do not have an effect on it
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