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42
The quadtree and related hierarchical data structures
 ACM Computing Surveys
, 1984
"... A tutorial survey is presented of the quadtree and related hierarchical data structures. They are based on the principle of recursive decomposition. The emphasis is on the representation of data used in applications in image processing, computer graphics, geographic information systems, and robotics ..."
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Cited by 421 (11 self)
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A tutorial survey is presented of the quadtree and related hierarchical data structures. They are based on the principle of recursive decomposition. The emphasis is on the representation of data used in applications in image processing, computer graphics, geographic information systems, and robotics. There is a greater emphasis on region data (i.e., twodimensional shapes) and to a lesser extent on point, curvilinear, and threedimensional data. A number of operations in which such data structures find use are examined in greater detail.
Object Shape and Reflectance Modeling from Observation
, 1997
"... An object model for computer graphics applications should contain two aspects of information: shape and reflectance properties of the object. A number of techniques have been developed for modeling object shapes by observing real objects. In contrast, attempts to model reflectance properties of real ..."
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Cited by 189 (14 self)
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An object model for computer graphics applications should contain two aspects of information: shape and reflectance properties of the object. A number of techniques have been developed for modeling object shapes by observing real objects. In contrast, attempts to model reflectance properties of real objects have been rather limited. In most cases, modeled reflectance properties are too simple or too complicated to be used for synthesizing realistic images of the object. In this paper, we propose a new method for modeling object reflectance properties, as well as object shapes, by observing real objects. First, an object surface shape is reconstructed by merging multiple range images of the object. By using the reconstructed object shape and a sequence of color images of the object, parameters of a reflection model are estimated in a robust manner. The key point of the proposed method is that, first, the diffuse and specular reflection components are separated from the color image sequence, and then, reflectance parameters of each reflection component are estimated separately. This approach enables estimation of reflectance properties of real objects whose surfaces show specularity as well as diffusely reflected lights. The recovered object shape and reflectance properties are then used for synthesizing object images with realistic shading effects under arbitrary illumination conditions.
Six DegreeofFreedom Haptic Rendering Using Voxel Sampling
 Proc. ACM Siggraph, ACM
, 1999
"... A simple, fast, and approximate voxelbased approach to 6DOF haptic rendering is presented. It can reliably sustain a 1000 Hz haptic refresh rate without resorting to asynchronous physics and haptic rendering loops. It enables the manipulation of a modestly complex rigid object within an arbitraril ..."
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Cited by 132 (1 self)
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A simple, fast, and approximate voxelbased approach to 6DOF haptic rendering is presented. It can reliably sustain a 1000 Hz haptic refresh rate without resorting to asynchronous physics and haptic rendering loops. It enables the manipulation of a modestly complex rigid object within an arbitrarily complex environment of static rigid objects. It renders a shortrange force field surrounding the static objects, which repels the manipulated object and strives to maintain a voxelscale minimum separation distance that is known to preclude exact surface interpenetration. Force discontinuities arising from the use of a simple penalty force model are mitigated by a dynamic simulation based on virtual coupling. A generalization of octree improves voxel memory efficiency. In a preliminary implementation, a commercially available 6DOF haptic prototype device is driven at a constant 1000 Hz haptic refresh rate from one dedicated haptic processor, with a separate processor for graphics. This system yields stable and convincing force feedback for a wide range of user controlled motion inside a large, complex virtual environment, with very few surface interpenetration events. This level of performance appears suited to applications such as certain maintenance and assembly task simulations that can tolerate voxelscale minimum separation distances.
T.: A scalable parallel cellprojection volume rendering algorithm for 3d unstructured data
 In Proc. 1997 Symposium on Parallel Rendering
, 1997
"... Visualizing threedimensional unstructured data from aerodynamics calculations is challenging because the associated meshes are typically large in size and irregular in both shape and resolution. The goal of this research is to develop a fast, efficient parallel volume rendering algorithm for massiv ..."
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Cited by 36 (14 self)
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Visualizing threedimensional unstructured data from aerodynamics calculations is challenging because the associated meshes are typically large in size and irregular in both shape and resolution. The goal of this research is to develop a fast, efficient parallel volume rendering algorithm for massively parallel distributedmemory supercomputers consisting of a large number of very powerful processors. We use cellprojection instead of raycasting to provide maximum flexibility in the data distribution and rendering steps. Effective static load balancing is achieved with a round robin distribution of data cells among the processors. A spatial partitioning tree is used to guide the rendering, optimize the image compositing step, and reduce memory consump tion. Communication cost is reduced by buffering messages and by overlapping communication with rendering calculations as much as possible. Tests on the IBM SP2 demonstrate that these strategies provide high rendering rates and good scalability. For a dataset containing half a million tetrahedral cells, we achieve two frames per second for a 400x400pixel image using 128 processors.
Robust and fast modelling of 3D natural objects from multiple views
 SPIE Proceedings "Image and Video Processing II
, 1994
"... An algorithm for the robust and fast automatic construction of a 3D model of any real object using images from multiple views is presented. The images are taken from a real object rotating in front of a stationary calibrated CCD TV camera. The object silhouettes extracted from the input images, the ..."
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Cited by 32 (5 self)
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An algorithm for the robust and fast automatic construction of a 3D model of any real object using images from multiple views is presented. The images are taken from a real object rotating in front of a stationary calibrated CCD TV camera. The object silhouettes extracted from the input images, the related turntable positions and camera orientation are used to construct the volume model of the real object by applying the method of occluding contours. A keypoint in performing this method is a proper volume representation, characterized by low complexity and suitability for a fast computation of volume models. In the presented approach, each volume model is described by pillar–like volume elements (pillars) ensuring a computational complexity proportional to the size of the real object surface and enabling a fast and simple construction of the volume model. The fast performance is due to the simple projection feasibility of those pillars and the easy–to–perform intersection test for the object silhouette with the projected pillars. Results with real image sequences have confirmed the robustness of the developed algorithm even for the modelling of real objects with highly detailed and complex surfaces and the use of imperfect object silhouettes. 1
Shape from Rotation
 In IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'91
, 1990
"... This paper examines the construction of a 3D surface model of an object rotating in front of a camera. Previous research in depth from motion has demonstrated the power of using an incremental approach to depth estimation. In this paper, we extend this approach to more general motion and use a full ..."
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Cited by 28 (8 self)
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This paper examines the construction of a 3D surface model of an object rotating in front of a camera. Previous research in depth from motion has demonstrated the power of using an incremental approach to depth estimation. In this paper, we extend this approach to more general motion and use a full 3D surface model instead of a 2 1 = 2 D sketch. The algorithm starts with a flow field computed using local correlation. It then projects individual measurements into 3D points with associated uncertainties. Nearby points from successive frames are merged to improve the position estimates. These points are then used to construct a finite element surface model, which is itself refined over time. We demonstrate the application of our new techniques to several real image sequences. Keywords: Computer vision, 3D model construction, image sequence (motion) analysis, optic flow, Kalman filter, surface interpolation, computer aided design, computer graphics animation. c flDigital Equipment C...
Neighbour finding in images represented by octrees
 Computer Vision, Graphics and Image Processing
, 1989
"... Algorithms are presented for moving between adjacent blocks in an octree representation of an image. Motion is possible in the direction of a face, edge, and a vertex, and between blocks of arbitrary size. The algorithms are based on a generalization and simplification of techniques developed earlie ..."
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Cited by 16 (6 self)
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Algorithms are presented for moving between adjacent blocks in an octree representation of an image. Motion is possible in the direction of a face, edge, and a vertex, and between blocks of arbitrary size. The algorithms are based on a generalization and simplification of techniques developed earlier for two dimensions (i.e., in quadtrees). They are also applicable to quadtrees. The difference lies in the graphtheoretical classification of adjacenciesi.e., in terms of vertices, edges, and faces. Algorithms are given for octrees that are implemented with pointers and with pointerless representations such as the linear octree. 0 1989 Academic PRSS. ITIC. 1.
Achieving Dextrous Grasping By Integrating Planning and Vision Based Sensing
, 1995
"... This paper deals with the automation of dextrous grasping in a partly known environment using a stereo vision system and a multifingered hand mounted on a robot arm. Effective grasping requires a combination of sensing and planning capabilities: sensing to construct a welladapted model of the situa ..."
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Cited by 12 (5 self)
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This paper deals with the automation of dextrous grasping in a partly known environment using a stereo vision system and a multifingered hand mounted on a robot arm. Effective grasping requires a combination of sensing and planning capabilities: sensing to construct a welladapted model of the situation and to guide the execution of the task, and planning to determine an appropriate grasping strategy and to generate safe, feasible manipulator motions. We propose an integrated approach that combines computer vision, path planning, and manipulator control in three complementary activities: the reconstruction of taskoriented models of the workspace, the determination of appropriate grasping configurations from computed `preshapes' of the hand, and the automatic generation and execution of hand/arm motions using a hybrid geometric path planner and a hybrid control system. This paper outlines the architecture of our system, discusses the new models and techniques we have developed, and fin...
Octree optimization
 In Symposium on Electronic Imaging Science and Technology, SPIE/SPSE. SPIE/SPSE
, 1990
"... ..."
Algorithms for the conversion of quadtrees to rasters
 IEEE Trans. Pattern Anal. and Machine Intelligence PAMI3
, 1981
"... A number of algorithms are presented for obtaining~a~i&?ter representation for an image given its quadtree. The algorithms are given in an evolutionary manner starting with the straightforward topdown approach that visits each run in a row in succession starting at the root of the tree. The remaini ..."
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Cited by 10 (5 self)
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A number of algorithms are presented for obtaining~a~i&?ter representation for an image given its quadtree. The algorithms are given in an evolutionary manner starting with the straightforward topdown approach that visits each run in a row in succession starting at the root of the tree. The remaining algorithms proceed in a manner akin to an inorder tree traversal. All of the algorithms are analyzed and an indication is given as to when each is preferable. The execution time of all of the algorithms is shown to be proportional to the sum of the heights of the blocks comprising the image. 1.