495 results about "Triangle mesh" patented technology

A method and apparatus are disclosed for finding a triangle mesh that interpolates a set of points obtained from a scanning system. A ball-pivoting algorithm computes a triangle mesh interpolating a given point cloud. The disclosed ball-pivoting algorithm triangulates a set of points by “rolling” a ball of radius r on the point cloud. The points are surface samples acquired with multiple range scans of an object. The ball-pivoting algorithm starts with a seed triangle, and pivots the ball of a given radius, r, around an edge of the triangle. During the pivoting operation, the ball revolves around the edge while keeping in contact with the edge's endpoints. The ball pivots until it touches another scan point, forming another triangle. The ball-pivoting operation continues until all reachable edges have been tried, and then starts from another seed triangle, until all scan points have been considered.

In the present invention, an apparatus for behavior analysis and method thereof is provided. In this apparatus, each behavior is analyzed and has its corresponding posture sequence through a triangulation-based method of triangulating the different triangle meshes. The two important posture features, the skeleton feature and the centroid context, are extracted and complementary to each other. The outstanding ability of posture classification can generate a set of key postures for coding a behavior sequence to a set of symbols. Then, based on the string representation, a novel string matching scheme is proposed to analyze different human behaviors even though they have different scaling changes. The proposed method of the present invention has been proved robust, accurate, and powerful especially in human behavior analysis.

The invention relates to a scattered point cloud Delaunay triangulation curved surface reconstruction method based on a mapping method and belongs to the field of a computer graphics and virtual reality technology. The method specifically includes the first step of obtaining original point cloud data of a target, the second step of obtaining K-level neighborhoods and unit normal vectors of all points in the original point cloud data, the third step of fragmenting the point cloud data, the fourth step of parameterizing fragmented point clouds to a two-dimensional plane, the fifth step of conducting Delaunay triangulation on the point clouds in the two-dimensional plane and mapping the point clouds back to corresponding three-dimensional space, and the sixth step of optimizing an initial triangle mesh model. Compared with the prior art, the scattered point cloud Delaunay triangulation curved surface reconstruction method based on the mapping method has the advantages that the quality of a triangle mesh can be ensured and triangle meshing on the scattered point clouds can be quickly realized when mesh modeling is carried out on large-scale point cloud data, and the method has a better effect on large-scale point clouds.

An apparatus for generating 3D geographical models includes a processor and memory storing executable computer program code causing the apparatus to at least perform operations including removing points of a cloud depicting vertical structures in meshes of triangles detected in an area corresponding to a set of 3D points responsive to identifying triangles on vertical structures. The triangles include vertices corresponding to geocoordinates. The program code further causes the apparatus to interpolate non-vertical structures of triangles to generate a dense cloud of points. The program code further causes the apparatus to downward project delineated points of segmented rooftops to closest points of a ground to generate 3D polygonal models depicting geographical objects. The program code further causes the apparatus to generate texturized objects responsive to mapping triangle locations to the 3D polygonal models and assign texture to vertical structures and rooftops. Corresponding methods and computer program products are also provided.

The invention provides a digital ship model plane motion organization experimental method based on computation fluid dynamics CFD software FLUENT. The method includes applying a FLUENT pre-process software GAMBIT to establish a research object model and a control domain; arranging a triangle grid on the model surface, then arranging a unstructured grid in the control domain; setting the boundary condition, joining an user-defined function UDF document, introducing dynamic grid technology, using a finite volume method based on the complete unstructured grid, realizing a pure swaying movement, a pure rising and falling movement, a pure oscillatory movement, a pure pitching movement and a pure rolling movement carried on by a plane motion organization experiment; applying a science computation software MATLAB to do Fourier expansion of a force and a moment coefficient obtained by the FLUENT, being fitted by EXCEL least squares method, obtaining a hydrodynamic force coefficient of a vertical plane and a horizontal plane as well as the related hydrodynamics analysis by dimensionless. The invention carries on the digit plane motion organization experiment using the CFD software, can satisfy the request of hydrodynamic force data in the design initial period of a submersible.

The invention belongs to the technical field of model segmentation in digital geometry processing, and discloses a method suitable for segmenting a dental triangle mesh curved surface from a dental jaw triangle mesh curved surface. The method integrates the three advantages of accuracy, high efficiency and smooth boundary, and finally realizes segmentation of the dental triangle mesh curved surface by the operations of interactive pickup of a dental jaw area to be segmented, primary segmentation of the increased area, automatic generation and accurate positioning of a spatial control curve, generation of segmentation line projection, smooth optimization of a segmentation line and the like.

The invention discloses a cutting method based on an integrated three-dimensional GIS model. The cutting method comprises the following steps that: cutting paths are defined; expression mode conversion is performed on different data models in the integrated three-dimensional GIS model, and spatial indexes are constructed for potential cutting objects; collision detection is performed so as to precisely determine whether the objects are involved in cutting, and surface triangles which intersect with cutting surfaces are obtained fast; triangle pairs which are subjected to cutting in a triangle mesh of the cutting surfaces and cut objects are obtained, and intersection computation is performed; repeat points are removed, and cutting intersecting lines in cut models are tracked; and cutting structure display can be formed according to structure types of cutting bodies. According to the invention, unified cutting operation is performed on the three-dimensional GIS model, and perception for inner structures of different types of objects can be realized, and reference to the results of interplay between different objects can be provided, and defects of the application of traditional cutting analysis to a three-dimensional GIS can be eliminated, and cutting efficiency can be effectively improved.

Disclosed is a method for calculating core neutron flux distribution of a small experimental reactor. The method includes steps of 1), determining geometrical and material parameters according to a core structure of the small experimental reactor, and establishing a neutron-transport equation describing movement rules of neutrons in each discrete direction inside a reactor core; 2), preparing corresponding quadrature sets for boundaries unparallel in normal surface vectors and each coordinate axis direction; 3), subjecting the neutron-transport equation to numerical discretion to acquire simultaneous linear algebraic equations of angular neutron flux density by a segment method of approximating unstructured geometry with unstructured grids to establish arbitrary triangular grids; 4), solving the simultaneous linear algebraic equations to acquire the discrete distribution of the angular neutron flux density in the reactor core, and acquiring the discrete distribution of neutron-flux density in the reactor core by the aid of relation of the angular neutron flux density and the neutron-flux density. By the method, the neutron-flux distribution of the small experimental reactor, especially that of an isotope production reactor, a pebble bed reactor and a high-flux reactor in the medical field can be accurately acquired.

Provided is a method and device for simultaneous positioning and map building based on vectors. The method is used for conducting three-dimensional (3D) positioning and map building in an unknown environment. The method includes: using an unknown visual angle to obtain a frame of point cloud data; conducting triangular meshing on the obtained point cloud data so as to form a plurality of planes and obtain normal vectors corresponding to each plane of the plurality of planes; combining adjacent normal vectors so as to obtain a normal vector list; obtaining an environment characteristic vector list of a known environment map; matching the normal vector list and vectors in the environment characteristic vector list; adding normal vectors in the normal vector list which is not matched to the environment characteristic vector list so as to update the environment characteristic vector list; calculating a rotation matrix by using matched vectors so as to calculate displacement; and finishing combining of a current frame and the known environment map according to a calculating result of the rotation matrix and the displacement.

The invention relates to a three-dimensional model segmenting device and a three-dimensional model segmenting method. The three-dimensional model segmenting method comprises the following steps: plane detection, which comprises detecting the plane in an input three-dimensional model which is described by a triangular grid; profile chart extraction, which comprises extracting the profile of the three-dimensional model, namely, the profile chart according to the plane detected in the plane detecting step; profile chart separation, which comprises segmenting the profile chart extracted in the profile chart extracting step into a plurality of sub charts; and three-dimensional solid rebuilding, which comprises rebuilding the three-dimensional solid models for each sub chart segmented from the profile chart separating step, wherein each rebuilt three-dimensional solid is expressed by the triangular grid.

The invention provides a method for segmenting a 3D model, comprising a bounded plane generating step, a skeleton graph extracting step and a skeleton graph segmenting step, wherein the bounded plane generating step is used for processing all the triangles included in the 3D model according to the input triangle mesh data of the 3D model to generate at least a bounded plane suitable for segmenting the 3D model; the skeleton graph extracting step is used for extracting the skeleton graph of the 3D model by the generated bounded plane; and the skeleton graph segmenting step is used for segmenting the extracted skeleton graph into a subgraph or at least two subgraphs which do not overlap with each other according to the information of the generated bounded plane and the information of the vertex adjacent graph of the 3D model. The invention also provides a device for segmenting the 3D model and an image processing system with the device. The method, the device and the system of the invention can improve the precision and efficiency of segmentation of the 3D model.

The invention discloses a modeling device of three-dimensional road intersections. The device comprises a conversion unit, a determining unit and a gridding unit, wherein the conversion unit utilizes three-dimensional road data with road intersections to convert a two-dimensional road to a three-dimensional road with the specified width and road edges; the determining unit obtains edge intersections corresponding to each two cross roads from the three-dimensional road and determines the road intersection areas of the three-dimensional road according to the turning radius and the edge intersections; and the gridding unit performs triangular gridding to the road intersection areas to obtain the model of the three-dimensional road intersections. By using the device of the invention, the modeling of the three-dimensional road intersection can be realized automatically and fast.

In a process for determining when tolerances are exceeded during generation of NC parts programs, the defined CAD geometry is converted into an equivalent grid, preferably a triangular grid. A surface corresponding to the NC parts programs in form of a triangular grid is generated after conversion of the CAD geometry. The parts program takes into consideration the geometric attributes of the milling tool (diameter, shape, etc.). After two triangular grids have been generated from the starting data, i.e. the CAD geometry and the NC parts program, the distance between the two grids can be calculated and visualized.

A feature edge extraction technique supports automatic creation of a solid model from a 3D or triangular mesh model. The technique extracts feature edges from the 3D mesh model according to a global normal-line evaluation method and an improved watershed method. The technique uses data related to the 3D mesh model, defines an area with a Euclidean distance, globally evaluates normals of triangles in the area, calculates edge and vertex feature values, carries out discretization and differentiation on the calculated vertex feature values, extracts feature edges satisfying requirements, divides the mesh model into segments each consisting of connected triangles according to the improved watershed method that is capable of grouping vertexes, extracts the boundaries of each segment as feature edges, allows a user to interactively select required feature edges from among the extracted feature edges, and outputs data related to the selected feature edges.

The invention discloses a method for meshing point cloud data. In the method, aiming at discrete point cloud data obtained by laser scanning, an automatic global parameterization method with strong robustness is provided, and a parameterization result is used for directly acquiring a meshing result which is consistent with a main direction and can reflect intrinsic geometric characteristics of a model. The meshing result has two forms, i.e., the meshing result can be wholly formed by quadrangles, or formed by triangles. By using the method, only the point cloud data of the model is used, prior triangulation is not needed to perform point cloud data meshing, the processing procedure is completely automatic, point clouds containing noises can be processed without manual intervention, and the density level of quadrangle meshing can be quickly controlled through parameters to obtain quadrilateral meshes or triangular meshes with various resolution ratios.

Triangulated shells can be free-formed but are uneconomical compared to translational shells that can only be flat. Scale-trans shells are limited in terms of number and arrangement of the openings. The present invention provides a free-formed, custom-tailored shell surface and a regularly shaped, mass-produced shell surface that can be assembled fairly evenly from advantageously quadrangular mesh elements having coplanar node points. The flexibility of a triangle net of shell pieces in a large scale is combined with the evenness of a quad net for meshes in a small scale, whereby triangular meshes at the shared side of adjoining square nets are combined in pairs to give irregular quadrangular meshes having coplanar vertices. The inventive shell is especially suitable for use as an energy-saving building such as a weekend home, emergency shelter, cupola of an observatory, roof of a building or an inner courtyard, as the shell of a large multi-story building or as a sports hall or factory building. It is also suitable as a part of a vault, and as a complex shell consisting of a single continuous surface for exhibition or station buildings. Parts of a Bohemian dome, cushion-roof, Isler shell or blob can be combined within any individual shell.

The invention provides a soft tissue deformation and cutting simulation method based on position dynamics. The method comprises the following four steps: grid preprocessing: according to an original triangular grid and a tetrahedron grid, and calculating a texture coordinate of each peak, calculating a set of edges in the grid, setting dynamics simulation parameters, and generating an improved tetrahedron grid; the deformation calculation of a soft tissue object: according to the current positions and the stressing situation of the peaks of the grids, calculating the positions of the peaks of the grids at a next moment according to the position dynamics; updating during grid topology change: according to an intersection situation of a cutting plane and grid intersection points, dividing an original tetrahedron, and updating the parameters of a geometric model and a position dynamics model; and visual rendering and touch rendering: displaying the soft tissue object and generating force feedback. The invention can truly simulate a process of cutting soft tissues in a virtual surgery, and exhibits high instantaneity.

A block model constructing method for complex geological structures is provided. The method comprises the following steps: a) making a triangle mesh description of a layer plane or a fault plane; b) judging whether two triangles intersect, and finding out the intersection points if they intersect; c) performing a geometric consistency and topological consistency processing within every intersectant triangle; d) extracting an enclosing block to acquire an interface constituted of peripheral edges of the enclosing block, and defining a geological attribute of the enclosing block to form a three-dimensional model block. The method needs not to solve difficult equation sets with large computation, thus simplifying the constructing method.

The invention discloses a self collision detection method based on a triangle mesh deformation body, comprising the steps of (1), constructing a data structure based on a hierarchical hounding volume (BVH); constructing an xBVH (expanded bounding volume hierarchy); constructing an SCTT (self-collision test tree)); optimizing star-shaped outline; (2), pre-processing self-collision detection based on the star-shaped outline; (3), performing self-collision test based on the star-shaped outline in real time. The method can detect the self-collision phenomenon during the deformation of the triangle mesh deformation body effectively in real time, accurately locates collision generation point and updates the collision information in real time.