171 results about "Tetrahedral meshes" patented technology

A novel and useful mechanism for the skinning of 3D meshes with reference to a skeleton utilizing statistical weight optimization techniques. The mechanism of the present invention comprises (1) an efficient high quality linear blend skinning (LBS) technique based on a set of skeleton deformations sampled from the manipulation space; (2) a joint placement algorithm to optimize the input skeleton; and (3) a set of tools for a user to interactively control the skinning process. Statistical skinning weight maps are computed using an as-rigid-as-possible (ARAP) optimization. The method operates with a coarsely placed initial skeleton and optimizes joint placements to improve the skeleton's alignment. Bones may also be parameterized incorporating twists, bends, stretches and spines. Several easy to use tools add additional constraints to resolve ambiguous situations when needed and interactive feedback is provided to aid users. Quality weight maps are generated for challenging deformations and various data types (e.g., triangle, tetrahedral meshes), including noisy, complex and topologically challenging examples (e.g., missing triangles, open boundaries, self-intersections, or wire edges).

The invention belongs to the technical field of mechanical analysis and numerical solution of a three-dimensional structure and relates to a contact analysis method in three-dimensional mechanical finite element model analysis. The method comprises the steps of firstly modeling a target electron device structure; introducing a displacement boundary condition or a stress boundary condition to establish a corresponding geometric structure model; generating a contact relation between parts according to a mutual relation between the parts; then subdividing the established geometric structure model by use of a tetrahedral mesh; generating a joint surface mesh according to a surface mesh in a simulated area contact surface; and finally establishing a finite element general intrinsic equation of a target electron device in consideration of a contact problem by use of a finite element method, solving the equation to obtain a characteristic value and a characteristic vector, and post-processing to obtain a vibration modal frequency and a vibration model. Therefore, the contact analysis in modal analysis is realized and a high-precision numerical calculation result is obtained.

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.

The triangular mesh generating portion divides the surface of geometry model to be meshed in a meshed manner according to a target element dimension and generates a triangular mesh on the surface of geometry model. The regular mesh generating portion assumes a shaped parallelpiped enclosing the shape to be meshed. The parallelpiped is divided in a meshed manner by the hexahedral element whose distance between the nodes has the substantially same density as the triangular mesh on the surface. The resulting regular mesh located inside the triangular mesh on the surface of geometry model is divided into a tetrahedral meshed manner. The shell meshing area extracting portion extracts a shell-like space between the inner tetrahedral mesh and the triangular mesh on the surface of geometry model. The shell mesh generating portion generates the tetrahedral mesh in the overall shape to be meshed.

An iterative method for determining a two—or—three-dimensional image on the basis of signals arising from X-ray tomography, comprises: segmenting the image by separating distinct materials respectively by level lines for 2D or level surfaces for 3D; and adapting the mesh, triangular for 2D or tetrahedral 3D, in which points are distributed in a homogeneous manner respectively over a level line for 2D or over a level surface for 3D, serving to formulate the progressively coarse triangular mesh for 2D or tetrahedral mesh for 3D, so that the number of distributed points depends respectively, for a line, on the ratio of the length of the line to the length of the minimum line from among the lines of the segmented image, or, for a surface, on the ratio of the area of the surface to the area of the minimum surface from among the surfaces of the segmented image.

The invention discloses a modeling method for MJ bolt and nut finite element meshes. The method comprises the following specific steps: I, summarizing geometrical features of a bolt and a nut; II, performing mathematical description on a thread zero-position section of the bolt; III, performing mathematical description on a thread zero-position section of the nut; IV, generating unthreaded region finite element meshes of the bolt and the nut; and V, generating thread node offsets of the bolt and the nut, and performing node movement on meshes on threads in order to obtain a threaded bolt. Through adoption of the modeling method, the MJ bolt and nut finite element meshes with threaded structure features can be generated rapidly and effectively. The meshes are hexahedron co-node meshes, so that errors caused by adoption of a TIE command or a tetrahedron mesh can be effectively avoided, and the calculation accuracy is increased greatly.

The invention relates to a finite element simulation method capable of removing a microwave tube high-frequency circuit in a pseudo-DC mode, comprising the flowing steps: (A) using a zero electric displacement vector as an electric field constraint equation and acquiring an integrated form of the electric field constraint equation according to an boundary value problem of an electromagnetic field in a microwave tube high-frequency circuit and acquiring a functional equation of the boundary value problem of the electromagnetic field through a standard variation principle of a finite element method; and (B) necessarily ensuring the match between grids on a main surface and grids on a secondary surface on a peripheral boundary when solving a solution domain and considering a pseudo-periodic boundary condition by adopting a dissection solution domain of tetrahedral grids. The invention has the advantages that the finite element simulation method can greatly improve the accuracy, the efficiency and the robustness of microwave tube high-frequency system simulation.

The invention discloses a coal bed high-pressure water injection fracturing-flow seeping value simulation method based on a shortest pressure relieving path algorithm. A coal body geometric model is built according to the water injection coal bed height, the strike length and the inclination length; a water injection hole model is added on the basis according to the water injection hole diameter, the length, the inclination angle and the hole sealing length parameter; a fracturing model is added according to the original fracture width, distribution and strike; finally, a combined body is formed through Boolean operation; the tetrahedron mesh generation is performed on the coal body geometric model; the mesh set which is easiest to damage is found, and is regarded as the generated fracture to be marked into the calculation fracture in the original geometric model; the algorithm step of finding the calculation fracture is repeated until all mesh intensity parameters are not lower than the received stress; the path formed by combining the obtained meshes is the shortest pressure relieving path, i.e., the fracture generating and development path is obtained. The water pressure fracturing is accurately simulated, and relevant data of the moving rule of moisture in the coal body is provided for decision makers.

The invention discloses a three-dimensional mesh model tetrahedralization method. The method comprises the following steps that (1), the initial position of a model is preprocessed; (2) a body centered cubic structure is established; (3) node symbols and points of tangency of boundries of a tetrahedron with the node symbols at the two ends opposite are calculated; (4) the points of tangency are moved; (5) the boundaries are tetrahedralized again. According to the three-dimensional mesh model tetrahedralization method, based on a body-centered cubic mesh tetrahedralization algorithm, preprocessing of principal component analysis of the three-dimensional model is added, a movement mode of the points of tangency of the boundaries of the model is changed, the points of tangency are moved to feature points of the model, and the positions of nodes of a final tetrahedral mesh are optimized through a density energy error function. After principal component analysis is adopted in the three-dimensional model, the quality of an initial tetrahedron element is improved; movement of the points of tangency to the feature points of the model is improved, so that local features of the tetrahedralized model are guaranteed; the quality of the final tetrahedral mesh is optimized through the density energy error function.

The invention relates to an intrinsic-analysis method for assigned frequency of a periodic structure, which includes steps: A, setting a functional equation which can consider boundary value of an electromagnetic field in conductors and medium loss periodic structure and can obtain the boundary value of the electromagnetic field by means of standard variation principle of the finite element method; B, solving solution domain by gridding subdivision of a tetrahedron and guaranteeing gridding matching of a primary side and a secondary side of the periodic boundary; C, selecting primary function, expanding electric-field intensity vector in all grids by the primary function and obtaining a matrix equation of expansion coefficient by Ritz method; D, writing the matrix equation of the expansion coefficient into a linear generalized intrinsic equation about propagation constant; E, solving the linear generalized intrinsic equation by setting a frequency, obtaining attenuation constant and phase constant corresponding to the set frequency according to the propagation constant, and obtaining interaction impedance through after treatment; and F, repeating the step of E to obtain attenuation constants, phase constants and interaction impedance corresponding to different frequency.

The invention relates to a dynamic solar tracking system for making optimal use of solar energy by means of panels of photovoltaic or thermal plates, in which a modular tracker adopting the configuration of a main beam which can be aligned with others of an identical nature is developed, this assembly of main beams being able to pivot with respect to its longitudinal axis, each of these beams being formed by a variable number of modules formed by profiles which as a whole provide each beam with a configuration by way of a tetrahedron mesh, and in each of which there is assembled a secondary beam structure for supporting the panels of plates, this secondary structure being supported by two side supports with respect to which it can rotate with respect to an axis transverse to the longitudinal direction of the main beams. The assembly incorporates control means for the automatic orientation of the panels, and a weather station for providing information to the control means.

An electronic device estimates a pose of a hand by volumetrically deforming a signed distance field using a skinned tetrahedral mesh to locate a local minimum of an energy function, wherein the local minimum corresponds to the hand pose. The electronic device identifies a pose of the hand by fitting an implicit surface model of a hand to the pixels of a depth image that correspond to the hand. The electronic device uses a skinned tetrahedral mesh to warp space from a base pose to a deformed pose to define an articulated signed distance field from which the hand tracking module derives candidate poses of the hand. The electronic device then minimizes an energy function based on the distance of each corresponding pixel to identify the candidate pose that most closely approximates the pose of the hand.

The invention discloses a method and system for determining a feedback force in a virtual cardiovascular interventional operation training system. The method includes the following steps that: displacement trajectory segments of a guide wire, topologic information of inner elements of the tetrahedral meshes of a blood vessel, and associated information of the triangular patches of the inner wall of the blood vessel and a space bounding box are obtained; based on the above results, whether the guide wire and the blood vessel collide is judged; if the guide wire and the blood vessel collide, the coordinates of a collision point and the coordinates of a force sense interaction device of a guide wire node are determined; and a virtual feedback force between the guide wire and the blood vessel is determined according to the coordinates of the collision point and the coordinates of the force sense interaction device of the guide wire node. With the method and system provided by the embodiments of the invention adopted, technical problems in accurately determining a virtual feedback force between a guide wire and a blood vessel in real time can be solved.

The invention discloses a method for modeling a three-dimensional finite element model. In accordance with a similar electromagnetic rail gun, a three-phase bus slot, such as power cable lines and tunnels, a 3-D entity with a planar symmetrical structure feature that that object is the main object is involved. In establishing the finite element model, first, a two-dimensional plane model is established, and then the finite element is divided into triangular meshes, the two-dimensional finite element model is stretched along the plane symmetry axis, at the different position of each main body object in the three-dimensional entity, the starting point of the segment stretch is determined, and the mesh is also divided in the axial direction during the stretching process, as the three-dimensional geometric model is formed, the corresponding three-dimensional finite element model is generated simultaneously, the finite element model generated by stretching is triangular prismatic mesh, andits mesh quality is better than that of tetrahedral mesh, which not only saves modeling time, but also ensures the mesh quality, and provides a new idea for the modeling method of three-dimensional finite element model of electromagnetic field numerical computation.

The invention provides a piston mesh division structure which is used for conducting CAE analysis on a piston. A mesh enveloping model of the piston comprises a first mesh model and a second mesh model, wherein the first mesh model envelops a piston body, and the second mesh model envelops a piston pin hole part of the piston body. The second mesh model is a hexahedral mesh enveloping model built on the piston pin hole part. CAE analysis meshes on the piston pin hole part are divided into hexahedral meshes, the hexahedral meshes are high in quality and uniform in density, contact analysis operation can be easily converged, the number of the hexahedral meshes is smaller than the number of tetrahedral meshes, and therefore high processing speed can be acquired, a more accurate analysis result can be acquired, and the solving speed of CAE analysis of the piston is higher.

The present invention belongs to the technical field of numerical analysis of three-dimensional thermal analysis and relates to a three-dimensional finite element simulation method based on heat radiation boundary conditions. The method comprises: carrying out modeling on a device to be subjected to the thermal analysis, introducing radiation boundary conditions into the heat conduction problem, and obtaining the finite element weak form of the heat radiation boundary conditions by adopting the method of Galerkin residual weighting; using the tetrahedral meshed model to select the second-orderlaminated basis function and the discrete finite element weak form equation, obtaining a finite element matrix and aright-end vector by cooperating with the Newton-Raphson iteration method, and integrating the final equation; and finally, by using the scientific nonlinear convergence criteria, through continuous iteration, quickly and accurately obtaining final numerical results.

A real-time simulation method of elastic materials based on an exemplar in a Laplace-Beltrami shape space includes the steps that by means of a Laplace-Beltrami operator and a linear finite element discretization method, characteristic functions and characteristic values of a simulation object and the exemplar on a three-dimensional tetrahedral mesh are calculated; the characteristic function of the exemplar and the characteristic function of the simulation object are subjected to registration; the position of the simulation object is projected in the Laplace-Beltrami shape space, and the shape of a target on an exemplar fashion is solved through non-linear shape interpolation; a final deformation result under an Euclidean space is obtained by building a local coordinate system on each vertex at current moment and adding shape details; a deformed object simulation kinetic equation under a non-inertial system is solved by means of a dimensionality reduction subspace built on a modal substrate, and displacement under a dimensionality reduction space at a new moment is obtained; the displacement under the dimensionality reduction space is projected to obtain global displacement by means of a projection matrix calculated in the preprocessing process under global and dimensionality reduction spaces, and a deformation result is drawn.