CN108537797B - The distortion of the mesh optimization method of deformable objects cutting simulation in a kind of virtual operation - Google Patents
The distortion of the mesh optimization method of deformable objects cutting simulation in a kind of virtual operation Download PDFInfo
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- CN108537797B CN108537797B CN201810330105.1A CN201810330105A CN108537797B CN 108537797 B CN108537797 B CN 108537797B CN 201810330105 A CN201810330105 A CN 201810330105A CN 108537797 B CN108537797 B CN 108537797B
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Abstract
The present invention provides a kind of distortion of the mesh optimization method of deformable objects cutting simulation in virtual operation, using geometry optimization and topological optimization, and combines multi-threading to multiple tasks parallel processing, to the ill unit problem for solving to occur during cutting simulation.This method includes four steps, and first, object element is searched for, grid cell to be treated is searched for according to mesh quality；Second, grid optimization pretreatment；Third, network topology optimization process；4th, grid geometry optimization process.Wherein Step 2: three, four use multi-threading parallel process.The present invention can reduce number of grid while improving mesh quality, can effectively improve efficiency and stability that grid model deformation calculates.
Description
Technical field
The present invention relates to a kind of methods in virtual operation cutting simulation, more particularly, to deformable in a kind of virtual operation
The distortion of the mesh optimization method of object cutting emulation.
Background technique
The operating platform that virtual operation provides virtual surgical environments for doctor and can interact, can be used for performing the operation rule
It draws, operative training, surgical simulation teaching etc..Compared with traditional operative training and operation teaching, virtual operation is at low cost, and
Repeatable operation.With the continuous development of virtual reality technology and the continuous promotion of computer hardware performance, virtual operation is obtained
More and more extensive research.The cutting simulation of deformable objects is the technology that one in virtual operation is basic, crucial, empty
Quasi- operation requires the cutting simulation of deformable objects accuracy with higher and real-time.
The cutting simulation of current deformable objects is largely the method based on grid, and the cutting based on tetrahedral grid
Emulation mode is method most widely used at present.Tetrahedral grid can construct the mould of almost arbitrary shape by grid subdivision
Type, but will appear ill unit during grid is generated with grid dividing, deformation simulation can be greatly reduced in ill unit
Computational efficiency and stability, and grid dividing can greatly increase number of grid, cause computation burden excessive, influence emulation
Accuracy and real-time.Therefore it is always the research hotspot of cutting simulation for the processing of grid, how effectively controls grid
Quality and quantity, the problem of being up to the present still a very challenging property.
The invention proposes a kind of distortion of the mesh optimization methods of deformable objects cutting simulation in virtual operation.Using several
What optimization and topological optimization, and combine multi-threading to multiple tasks parallel processing, it can be during solving cutting simulation
Number of grid is reduced while the ill unit problem of appearance, the effective efficiency and stabilization for improving grid model deformation and calculating
Property.
Summary of the invention
The purpose of the present invention is to solve the ill unit problems in virtual operation deformable objects cutting simulation, improve
The mesh quality of model improves the efficiency and stability of cutting simulation, and deformable objects are cut in a kind of virtual operation proposed
Cut the distortion of the mesh optimization method of emulation.
The present invention provides a kind of distortion of the mesh optimization method of deformable objects cutting simulation in virtual operation, this method packet
Include four steps:
The first step searches for object element, searches for grid cell to be treated according to mesh quality, each object element is handed over
Subsequent processing is done to a thread, specific as follows:
(a) it for volume mesh, is searched according to the volume length ratio criteria of volume mesh quality in the part for executing cutting operation
Rope object element；
(b) for surface grids, according to the Area length ratio criteria of surface grids quality in the search mesh for executing cutting operation
Mark unit；
If (c) searching, two or more object elements is adjacent, the polygon or polyhedron that it is constituted as
New object element；
(d) object element searched is stored into object element queue, and be sequentially allocated subsequent to sub thread execution
Step.
Second step, grid optimization pretreatment, is handled local target area according to the object element searched, specifically
It is as follows:
(a) it determines peripheral unit, utilizes advantage search and the object element (surface mesh of K-D data tree structure proximity search
Lattice or volume mesh) there is the peripheral unit of connection relationship on vertex；
(b) vertex of delete target unit, and the connection relationship of each vertex and peripheral unit is deleted, to obtain target
Region, target area are a polygon (or polyhedron)；
(c) topological structure of grid model is updated according to the connection relationship between vertex.
Third step, network topology optimization process repartition grid and more to the grid model for having executed pre-treatment step
New topological structure improves object element mesh quality, specific as follows:
(a) grid is repartitioned to target area, executes Delaunay using the boundary and internal point set of target area and cuts open
Point；
(b) judge whether mesh quality meets the requirements, execute (d) if meeting the requirements, otherwise (c) is executed, according to first
Quality standard (1) described in step search object element and (2) judge whether the unit in target area meets the requirements；
(c) new summit is added in target area and determines vertex position, executes (a) later, the new summit position is
Maximum triangle or the tetrahedral circumscribed circle center of circle in target area, maximum triangle or tetrahedron are circumscribed circle in target area
The maximum unit of radius；
(d) topological structure that grid model is updated according to the connection relationship between vertex, if not adding new node,
The surface laplacian for directly executing the 4th step is smooth.
4th step, grid geometry optimization process do geometry optimization to the grid for having executed topological optimization, adjust vertex position
It sets, further improves mesh quality, specific as follows:
(a) grid relaxation is executed to target area volume mesh；
(b) smooth to the local surfaces grid execution Laplce after cutting, each node of local surfaces grid is moved
Move the mean place of its adjacent node.
Wherein Step 2: each target area involved in three, four is used as an individual task to be delivered to thread pool
Do parallel processing.
Advantage is the present invention compared with prior art:
1. individually handling each ill unit, local optimum is carried out to it respectively, mesh quality can be improved, and will not
Influence other grids.
2. using geometry optimization and topological optimization, and combine multi-threading to multiple tasks parallel processing, can solve
Number of grid is reduced while the ill unit problem certainly occurred during cutting simulation, it is effective to improve grid model deformation gauge
The efficiency and stability of calculation.
3. accelerate effectively to improve search speed to the search process of peripheral unit using K-D tree construction combination multithreading,
Meet the requirement of real-time in Virtual cropping.
Detailed description of the invention
A kind of Fig. 1: the flow chart of the distortion of the mesh optimization method of deformable objects cutting simulation in virtual operation；
Fig. 2: the two-dimensional representation of object element and target area；
Specific embodiment
Fig. 1 gives a kind of flow chart of the distortion of the mesh optimization method of deformable objects cutting simulation in virtual operation,
The present invention is further illustrated With reference to embodiment.
The present invention provides a kind of distortion of the mesh optimization methods of deformable objects cutting simulation in virtual operation, main to walk
Suddenly it is described below:
The first step searches for object element, searches for grid cell to be treated according to mesh quality, each object element is handed over
Subsequent processing is done to a thread,
(a) node of grid model is stored in three-dimensional K-D tree, by the relevant grid cell (tetrahedron of different nodes
Or tri patch) be saved in a Hash table and to its real-time update；
(b) it for volume mesh, is searched according to the volume length ratio criteria of volume mesh quality in the part for executing cutting operation
Rope object element
Wherein ej(j=1,2,3,4,5,6) is the length on six sides of tetrahedral grid, and V is the volume of tetrahedral grid,
QV∈ (0,1), QVValue closer to 1, illustrate that the quality of tetrahedral grid is higher, QVWhen=1, grid cell is positive tetrahedron, if
Determining threshold value is 0.3, searches for QVIt is worth the tetrahedron element less than 0.3；
(c) for surface grids, according to the Area length ratio criteria of surface grids quality in the search mesh for executing cutting operation
Mark unit
Wherein ej(j=1,2,3) is the length on three sides of tri patch, and A is the area of tri patch, QF∈ (0,1),
QFValue closer to 1, illustrate that the quality of triangular mesh is higher, QFWhen=1, grid cell is equilateral triangle, as shown in Figure 2 with
For 2D situation, figure intermediate cam shape ABC is the object element searched, and given threshold 0.3 searches for QFValue is less than 0.3
Tetrahedron element；
If (d) searching, two or more object elements is adjacent, the polygon or polyhedron that it is constituted as
New object element；
(e) object element searched is stored into object element queue, and be sequentially allocated subsequent to sub thread execution
Step.
Second step, grid optimization pretreatment, is handled local target area according to the object element searched,
(a) it determines peripheral unit, utilizes advantage search and the object element (surface mesh of K-D data tree structure proximity search
Lattice or volume mesh) there is the peripheral unit of connection relationship on vertex, as shown in Fig. 2, ABC is object element, dotted line is shown in periphery list
The connection of member；
(b) vertex of delete target unit, and the connection relationship of each vertex and peripheral unit is deleted, to obtain target
Region, target area is a polygon (or polyhedron), as shown in Fig. 2, the object element that solid line indicates；
(c) topological structure of grid model is updated according to the connection relationship between vertex.；
Third step, network topology optimization process repartition grid and more to the grid model for having executed pre-treatment step
New topological structure improves object element mesh quality,
(a) grid is repartitioned to target area, executes Delaunay using the boundary and internal point set of target area and cuts open
Point；
(b) judge whether mesh quality meets the requirements, execute (d) if meeting the requirements, otherwise (c) is executed, according to first
Quality standard (1) described in step search object element and (2) judge whether the unit in target area meets the requirements；
(c) new summit is added in target area and determines vertex position, executes (a) later, the new summit position is
Maximum triangle or the tetrahedral circumscribed circle center of circle in target area, maximum triangle or tetrahedron are circumscribed circle in target area
The maximum unit of radius；
(d) topological structure that grid model is updated according to the connection relationship between vertex, if not adding new node,
Directly execute the smooth surface of the 4th step.
4th step, grid geometry optimization process do geometry optimization to the grid for having executed topological optimization, adjust vertex position
It sets, further improves mesh quality,
(a) grid relaxation is executed to target area volume mesh, following behaviour is carried out for each node in target area
Make,
Wherein, (xi,yi,zi) be destination node coordinate, (xp,yp,zp) be destination node coordinate adjusted, N be with
Destination node has the sum of all nodes of connection relationship；
Quality estimation is carried out to the grid adjusted, judgment criteria is as follows:
Wherein QRTo be associated with quality coefficient (0 < QR≤ 1), QViFor the quality mark for searching for object element described in the first step
Standard, wherein QViFor the tetrahedral quality coefficient comprising destination node,QRIt is bigger, grid
Quality is higher；
If destination node adjusted is located in target area and than the Q of destination node before adjustingRValue is big, then by target
Otherwise node motion is enabled to position adjusted
xp=(xp+xi)/2,yp=(yp+yi)/2,zp=(zp+zi)/2 (5)
Circulation carries out aforesaid operations later, until mesh quality meets quality criteria or cycle-index reaches the upper limit, follows
The ring upper limit is independently arranged by user；
(b) smooth to the local surfaces grid execution Laplce after cutting, each node of local surfaces grid is moved
Move the mean place of its adjacent node.
Wherein Step 2: each target area involved in three, four is used as an individual task to be delivered to thread pool
Do parallel processing.
Claims (1)
1. the distortion of the mesh optimization method of deformable objects cutting simulation in a kind of virtual operation, it is characterised in that realize step such as
Under:
The first step searches for object element, searches for grid cell to be treated according to mesh quality, each object element gives one
A thread does subsequent processing；
Second step, grid optimization pretreatment, is handled local target area according to the object element searched；
Third step, network topology optimization process are repartitioned grid and are updated and open up to the grid model for having executed pre-treatment step
Structure is flutterred, object element mesh quality is improved；
4th step, grid geometry optimization process do geometry optimization to the grid for having executed topological optimization, adjust vertex position, into
The improvement mesh quality of one step；
Wherein Step 2: each target area involved in three, four is used as an individual task to be delivered to thread pool does simultaneously
Row processing；
(1) search object element described in the first step is,
(a) node of grid model is stored in three-dimensional K-D tree, by the relevant grid cell of different nodes, i.e., tetrahedron or
Tri patch is saved in a Hash table and to its real-time update；
(b) for volume mesh, according to the volume length ratio criteria of volume mesh quality in the local search mesh for executing cutting operation
Mark unit
Wherein ej(j=1,2,3,4,5,6) is the length on six sides of tetrahedral grid, and V is the volume of tetrahedral grid, QV∈
(0,1), QVValue closer to 1, illustrate that the quality of tetrahedral grid is higher, QVWhen=1, grid cell is positive tetrahedron, sets threshold
Value is 0.3, searches for QVIt is worth the tetrahedron element less than 0.3；
(c) for surface grids, according to the Area length ratio criteria of surface grids quality in the local search mesh for executing cutting operation
Mark unit
Wherein ej(j=1,2,3) is the length on three sides of tri patch, and A is the area of tri patch, QF∈ (0,1), QF's
Value illustrates that the quality of triangular mesh is higher, Q closer to 1FWhen=1, grid cell is equilateral triangle, given threshold 0.3,
Search for QFIt is worth the triangular element less than 0.3；
If (d) searching, two or more object elements is adjacent, and the polygon or polyhedron that it is constituted are as new
Object element；
(e) object element searched is stored into object element queue, and is sequentially allocated and executes subsequent step to sub thread；
(2) grid optimization described in second step, which pre-processes, is,
(a) determine peripheral unit, using K-D tree proximity search advantage search and object element, i.e., with surface mesh or body net
There is the peripheral unit of connection relationship on lattice vertex；
(b) vertex of delete target unit, and the connection relationship of each vertex and peripheral unit is deleted, to obtain target area
Domain, target area are a polygon or polyhedron；
(c) topological structure of grid model is updated according to the connection relationship between vertex；
(3) network topology optimization process described in third step is,
(a) grid is repartitioned to target area, executes Delaunay subdivision using the boundary and internal point set of target area；
(b) judge whether mesh quality meets the requirements, directly execute (d) if meeting the requirements, otherwise (c) is executed, according to first
Quality standard (1) described in step search object element and (2) judge whether the unit in target area meets the requirements；
(c) new summit is added in target area and determines vertex position, executes (a) later, and the new summit position is target
Maximum triangle or the tetrahedral circumscribed circle center of circle in region, the maximum triangle or tetrahedron are circumscribed circle in target area
The maximum unit of radius；
(d) topological structure that grid model is updated according to the connection relationship between vertex, if not adding new node, directly
The Laplce executed in the 4th step grid geometry optimization is smooth；
Grid geometry optimization process described in (4) the 4th steps is,
(a) grid relaxation is executed to target area volume mesh, following operation is carried out for each node in target area,
Wherein, (xi,yi,zi) be destination node coordinate, (xp,yp,zp) it is destination node coordinate adjusted, N is and target
Node has the sum of all nodes of connection relationship；
Quality estimation is carried out to the grid adjusted, judgment criteria is as follows:
Wherein QRTo be associated with quality coefficient (0 < QR≤ 1), QViFor described in the first step search for object element quality standard,
Middle QViFor the tetrahedral quality coefficient comprising destination node,QRBigger, mesh quality is got over
It is high；
If destination node adjusted is located in target area and than the Q of destination node before adjustingRValue is big, then by destination node
It is moved to position adjusted, is otherwise enabled
xp=(xp+xi)/2,yp=(yp+yi)/2,zp=(zp+zi)/2 (5)
Circulation carries out aforesaid operations later, until meeting quality standard or reaching the circulation upper limit；
(b) smooth to the local surfaces grid execution Laplce after cutting, each node motion of local surfaces grid is arrived
The mean place of its adjacent node.
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| CN111168990B (en) * | 2019-12-30 | 2021-04-09 | 浙江大学 | Biological 3D printing device and method capable of realizing online detection and real-time correction |
| CN111222242A (en) * | 2020-01-06 | 2020-06-02 | 广州中国科学院工业技术研究院 | Method for geometric cutting and grid optimization based on grid and electronic equipment |
| CN113742809B (en) * | 2021-11-04 | 2022-02-11 | 山东神力索具有限公司 | Rigging grid adjusting method and device and electronic equipment |
| CN114781232B (en) * | 2022-06-17 | 2022-09-16 | 中汽研（天津）汽车工程研究院有限公司 | Method, device and storage medium for automatically adjusting quality of finite element mesh |
| CN115495968B (en) * | 2022-11-21 | 2023-06-02 | 广州中望龙腾软件股份有限公司 | Grid dividing method, terminal and storage medium |
| CN116562065B (en) * | 2023-07-12 | 2023-09-12 | 北京凌云智擎软件有限公司 | Mesh topology conversion method, device and apparatus |
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