Local Matching of Surfaces Using Critical Points

The local matching problem on surfaces is: Given a pair of oriented surfaces in 3-space, find subsurfaces that are identical or complementary in shape. A heuristic method is presented for local matching that is intended for use on complex curved surfaces (rather than such surfaces as as cubes and cylinders). The method proceeds as follows: (1) Find a small set of points-called critical points -on the two surfaces with the property that if p is a critical point and p matches q, then q is also a critical point. The critical points are taken to be local extrema of either Gaussian or mean curvature. (2) Construct a rotation invariant representation around each critical point by intersecting the surface with spheres of standard radius centered around the critical point. For each of the resulting curves of intersection, compute a distance map function equal to the distance from a point on the curve to the center of gravity of the curve as a. function of arc length (normalized so that the domain of the function is the interval [0,1]). Cll the set of contours for a given critical point a distance profile. (3) Match distance profiles by computing a correlation between corresponding distance contours. (4) Use maximal compatible subsets of the set of matching profiles to induce a transformation that maps corresponding critical points together, then use a cellular spatial partitioning technique to find all points on each surface that are within a tolerance of the other surface

TEMPUS: A System for the Design and Simulation of Human Figures in a Task-Oriented Environment

A system called TEMPUS is outlined which is being developed to simulate graphically the task-oriented activities of several human agents in a three-dimensional environment. TEMPUS is a task simulation facility for the evaluation of complex workstations vis-a-vis the normal and emergency procedures they are intended to support and the types and number of individuals who must carry them out. TEMPUS allows a user to interactively: * Create one or more human figures which are correctly scaled according to a specific population, or which meet certain size constraints. * View the human figure in any of several graphical modes: stick figure, line or shaded polygons, or shaded BUBBLEPERSON. * Position the figure in any admissible position within joint angle constraints, and with the assistance of a robotics reach positioning algorithm for limbs. * Combine the figures with three-dimensional polyhedral objects derived from an existing CAD system. * Create shaded graphics images of bodies in such environments. * Use all TEMPUS features in an extensible and uniform user-friendly interactive system which does not require any explicit programming knowledge. A brief summary of the software engineering of this system in a University environment is included. Other features of TEMPUS and differences between TEMPUS and other available body modeling systems are also discussed

TEMPUS: A System for the Design and Simulation of Human Figures in a Task-Oriented Environment

A system called TEMPUS is outlined which is being developed to simulate graphically the task-oriented activities of several human agents in a three-dimensional environment. TEMPUS is a task simulation facility for the evaluation of complex workstations vis-a-vis the normal and emergency procedures they are intended to support and the types and number of individuals who must carry them out. TEMPUS allows a user to interactively: Create on or more human figures which are correctly scaled according to a specific population, or which meet certain size constraints. View the human figure in any of several graphical modes: stick figure, line or shaded polygons, or shaded BUBBLEPERSON. Position the figure in any admissible position within joint angle constraints, and with the assistance of a robotics reach positioning algorithm for limbs. Combine the figures with three-dimensional polyhedral objects derived from an existing CAD system. Create shaded graphics images of bodies in such environments. Use all TEMPUS features in an extensible and uniform user-friendly interactive system which does not require any explicitly programming knowledge. Other features of TEMPUS and differences between TEMPUS and other available body modeling systems are also discussed

LOCAL MATCHING OF SURFACES USING BOUNDARY-CENTERED RADIAL DECOMPOSITION

The local matching problem on surfaces is: Given a pair of oriented surfaces in 3-space, find subsurfaces that are identical or complementary in shape. A heuristic solution is presented that is intended for use on complex surfaces (as opposed to such things as cubes and cylinders). The method proceeds as follows: (1) Find a small set of points--called critical points --on the two surfaces with the property that if p is a critical point and p matches q, then q is also a critical point. The critical points are taken to be local extrema of curvature, either Gaussian or mean. (2) Construct a rotation invariant representation around each critical point by intersecting the surface with spheres of standard radius centered around the critical point. For each of the resulting curves, compute a distance contour function equal to the distance from a point on the curve to the center of gravity of the curve as a function of arc length (normalized so that the domain of the function is the interval 0,1 ). Call the set of contours for a given critical point a distance profile. (3) Match distance profiles by computing a correlation between corresponding distance contours. (4) Use maximal compatible subsets of the set of matching profiles to induce a transformation that maps corresponding critical points together, then use a cellular spatial partitioning technique to find all points on each surface that are within a tolerance of the other surface. This method has been implemented using surfaces represented by polygonal networks as input. It has been successfully applied to synthetically produced surfaces. Applications include scene analysis, molecular docking (fitting) and assembly of three dimensional jigsaw puzzles

LOCAL MATCHING OF SURFACES USING BOUNDARY-CENTERED RADIAL DECOMPOSITION

The local matching problem on surfaces is: Given a pair of oriented surfaces in 3-space, find subsurfaces that are identical or complementary in shape. A heuristic solution is presented that is intended for use on complex surfaces (as opposed to such things as cubes and cylinders). The method proceeds as follows: (1) Find a small set of points--called critical points --on the two surfaces with the property that if p is a critical point and p matches q, then q is also a critical point. The critical points are taken to be local extrema of curvature, either Gaussian or mean. (2) Construct a rotation invariant representation around each critical point by intersecting the surface with spheres of standard radius centered around the critical point. For each of the resulting curves, compute a distance contour function equal to the distance from a point on the curve to the center of gravity of the curve as a function of arc length (normalized so that the domain of the function is the interval 0,1 ). Call the set of contours for a given critical point a distance profile. (3) Match distance profiles by computing a correlation between corresponding distance contours. (4) Use maximal compatible subsets of the set of matching profiles to induce a transformation that maps corresponding critical points together, then use a cellular spatial partitioning technique to find all points on each surface that are within a tolerance of the other surface. This method has been implemented using surfaces represented by polygonal networks as input. It has been successfully applied to synthetically produced surfaces. Applications include scene analysis, molecular docking (fitting) and assembly of three dimensional jigsaw puzzles

A Tool for Visually Browsing STEP Complexity

The Standard for the Exchange of Product Model Data (STEP) is one of the largest and most complex standardization efforts undertaken by mankind. STEP is a key enabling technology to achieve effective data transfer and collaboration within concurrent engineering practice. STEP data is voluminous, complex, and difficult to understand without visual assistance. Although much of this data is inherently visual, no tools have been developed permitting fully interactive browsing of the details in 3D. This paper describes the result of software efforts to visualize many of the complex details of STEP geometries and features. A valuable tool is presented which enables a user to interactively browse complex STEP product data in 3D. During the visual browsing process, important details such as features, geometry, and material, are revealed quickly for inspection and to aid understanding of STEP. 1: Introduction The fields of Computer-Aided Design (CAD), Computer-Aided Engineering (CAE), and Com..

ESC Guidelines on the diagnosis and treatment of peripheral artery diseases: Document covering atherosclerotic disease of extracranial carotid and vertebral, mesenteric, renal, upper and lower extremity arteries: the Task Force on the Diagnosis and Treatment of Peripheral Artery Diseases of the European Society of Cardiology (ESC).

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