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Representation of three-dimensional motion in dynamic scenes
COMPUTER GRAPHICS AND IMAGE PROCESSING 20, 296-297 (1982)
Abstracts
of Papers
Accepted
for Publication
PAPERS A Discrete Spatial Representation for Lateral Motion Stereo. NELSON J. BRIDWELL AND THO~S S. HUANG. Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801. Received February 26, 1982; revised July 16, 1982. A simple procedure generates the complete minimum depth surface description of a three-dimensionai scene that is consistent with a series of images from a laterally translating camera. The internal representation is a discrete map of intervening empty space between the camera and visible surfaces that is the result of occlusion and surface brightness constraints. The effectiveness of this algorithm is demonstrated on real and synthetic test images.
Dtkplacement Vectors Deriwd from Second Order Intensity Variations in Image Sequences. HAW.HELLMLJT NAGEL. Fachbereich Informatik, Universitaet Hamburg, Schlueterstrasse 70, 2000 Ham burg 13, Germany. Received March 11, 1982; revised April 7, 1982. A local approach for interframe displacement estimates is developed by minimization of the squared differences between a second order Taylor expansion of gray values from one frame and the observed gray values within the same window from the next frame. If the second order terms in the Taylor expansion are significant, a system of two coupled nonlinear equations for the two unknown components of the displacement vector can be derived. In the special case of “gray value comers,” these equations can be simplified to facilitate a closed form solution. An iterative refinement procedure is developed to extend these estimates for image regions which do not exhibit exactly the properties of “gray value comers.” ‘The minimization approach is generalized in such a way that the approach of Horn and Schunck 198 I can be recognized as a special case of this generalized form which should be applicable even across occluding edges. It thus appears to be an interesting model for the local computation of optical flow.
Representation of TVuee-Dimensional Motion in Dynamic Scenes. MINORU ASADA AND SABURO Tsur~ Department of Control Engineering, Osaka University, Toyonaka, Osaka 560, Japan. Received March 22, 1982; revised August 17, 1982. A framework is described that finds a meaningful representation of rigid and joint motion, given correspondences of points on each object in an image sequence. Objects in the input scene show complex motion such that an object rotates around an axis attached to another moving and rotating object. A geometrical model of rotation is introduced to explore relationships between an apparent rotation vector and actual rotations around multiple physical axes. Analysis of the rotational vectors mapped on a Gaussian sphere yields useful information such as a number of the multiple axes and their orientations. The structure of jointly moving objects is found by using these motion cues and is represented in a hierarchical form. In order to find a compact representation of the dynamic scene, the image sequence is partitioned into a small number of subsequences. Properties of translational components are useful for the segmentation; however, their representation is not unique, but two degrees of freedom are left. The freedom is used to make the motion representation simple and natural. Each short period in the image sequence is described as a constant velocity or a constant acceleration movement, and then a clustering method is used for the segmentation of the input sequence. and Correspon&nce. JON A. WEBB. Department of Computer Sciences, The University of Texas at Austin, Austin, Texas 78712. J. K. AGGARWAL. Department of Electrical Engineering, The University of Texas at Austin, Austin, Texas 78712. Received June 11, 1982; revised September 17. 1982. 296 0146-664X/82/1 10296-02$02OO/OO S-e
Copyright All rights
8 1982 by Academic Press, Inc. of reproduction in any form resewed.
Abstracts
of Papers
Accepted
for Publication
PAPERS A Discrete Spatial Representation for Lateral Motion Stereo. NELSON J. BRIDWELL AND THO~S S. HUANG. Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801. Received February 26, 1982; revised July 16, 1982. A simple procedure generates the complete minimum depth surface description of a three-dimensionai scene that is consistent with a series of images from a laterally translating camera. The internal representation is a discrete map of intervening empty space between the camera and visible surfaces that is the result of occlusion and surface brightness constraints. The effectiveness of this algorithm is demonstrated on real and synthetic test images.
Dtkplacement Vectors Deriwd from Second Order Intensity Variations in Image Sequences. HAW.HELLMLJT NAGEL. Fachbereich Informatik, Universitaet Hamburg, Schlueterstrasse 70, 2000 Ham burg 13, Germany. Received March 11, 1982; revised April 7, 1982. A local approach for interframe displacement estimates is developed by minimization of the squared differences between a second order Taylor expansion of gray values from one frame and the observed gray values within the same window from the next frame. If the second order terms in the Taylor expansion are significant, a system of two coupled nonlinear equations for the two unknown components of the displacement vector can be derived. In the special case of “gray value comers,” these equations can be simplified to facilitate a closed form solution. An iterative refinement procedure is developed to extend these estimates for image regions which do not exhibit exactly the properties of “gray value comers.” ‘The minimization approach is generalized in such a way that the approach of Horn and Schunck 198 I can be recognized as a special case of this generalized form which should be applicable even across occluding edges. It thus appears to be an interesting model for the local computation of optical flow.
Representation of TVuee-Dimensional Motion in Dynamic Scenes. MINORU ASADA AND SABURO Tsur~ Department of Control Engineering, Osaka University, Toyonaka, Osaka 560, Japan. Received March 22, 1982; revised August 17, 1982. A framework is described that finds a meaningful representation of rigid and joint motion, given correspondences of points on each object in an image sequence. Objects in the input scene show complex motion such that an object rotates around an axis attached to another moving and rotating object. A geometrical model of rotation is introduced to explore relationships between an apparent rotation vector and actual rotations around multiple physical axes. Analysis of the rotational vectors mapped on a Gaussian sphere yields useful information such as a number of the multiple axes and their orientations. The structure of jointly moving objects is found by using these motion cues and is represented in a hierarchical form. In order to find a compact representation of the dynamic scene, the image sequence is partitioned into a small number of subsequences. Properties of translational components are useful for the segmentation; however, their representation is not unique, but two degrees of freedom are left. The freedom is used to make the motion representation simple and natural. Each short period in the image sequence is described as a constant velocity or a constant acceleration movement, and then a clustering method is used for the segmentation of the input sequence. and Correspon&nce. JON A. WEBB. Department of Computer Sciences, The University of Texas at Austin, Austin, Texas 78712. J. K. AGGARWAL. Department of Electrical Engineering, The University of Texas at Austin, Austin, Texas 78712. Received June 11, 1982; revised September 17. 1982. 296 0146-664X/82/1 10296-02$02OO/OO S-e
Copyright All rights
8 1982 by Academic Press, Inc. of reproduction in any form resewed.