EP2904587A2 - Procédé de traitement de données définissant un élément dans un espace e de dimensions d, programme d'ordinateur associé - Google Patents
Procédé de traitement de données définissant un élément dans un espace e de dimensions d, programme d'ordinateur associéInfo
- Publication number
- EP2904587A2 EP2904587A2 EP13774392.8A EP13774392A EP2904587A2 EP 2904587 A2 EP2904587 A2 EP 2904587A2 EP 13774392 A EP13774392 A EP 13774392A EP 2904587 A2 EP2904587 A2 EP 2904587A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- intersection
- hyperplane
- mediating
- point
- sign
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
- G06T17/20—Finite element generation, e.g. wire-frame surface description, tesselation
Definitions
- the present invention relates to methods of data processing defining an element in a space E of dimensions d, comprising the following steps:
- al defines a set of n points in the space E;
- Such techniques are used, inter alia, to generate a mesh of an element such as a surface or a volume.
- Surface meshes are used in many technical applications, for example in the numerical simulation of flow for aeronautical design or for oil exploration, in the mechanics of structures for the design of frames, bridges and other structures. art, in the mechanics of deformations for the simulation of automobile impact tests etc.
- the mesh consists of cutting the element in question into a set of basic cells.
- Each base cell and the set of basic cells as a whole must satisfy predefined validity conditions, for example relating to the geometric shape of the basic cells (square, triangle, tetrahedron, hexahedron, cube, etc.) or on angle values at vertices (respect of minimum / maximum angle values).
- Voronoi Tessellation ", or” CVT ”
- ODT Optimal Delaunay Triangulation
- an anisotropic mesh that is to say which has elements that differ from each other in size. and / or in orientation, in predefined areas of the element.
- An anisotropy matrix is defined for each base cell specifying these orientation and size constraints.
- the document FR 2962582 describes an anisotropic mesh generation technique.
- an anisotropic element of dimension d0 for example 3D
- a corresponding isotropic element of dimension d for example 6D
- each deformed circle represents the equidistant points of the center of the deformed circle in terms of anisotropic distance defined by the anisotropic metric considered.
- an isotropic Voronoi diagram is then generated for this 3D surface, represented in part B of FIG. 2.
- an isotropic mesh by Delaunay triangulation represented in part C of FIG. 2, is deduced from this diagram of FIG. Vorono ⁇ .
- the isotropic 3D surfaces shown in parts A, B, C of FIG. 2 are projected on the (xOy) plane to generate the corresponding anisotropic 2D surfaces of parts A, B, C of FIG.
- references_1 Some of these techniques are notably exposed in the following documents, named references_1:
- the computation of a Delaunay triangulation has a complexity proportional to d !, where d is the dimension of the computing space.
- d is the dimension of the computing space.
- the dipping space has a dimension of 6D or even 10D, which makes the calculation volume prohibitive.
- the present invention aims at providing a solution for reducing the computing load in a space of dimension d.
- the invention proposes a data processing method of the aforementioned type, characterized in that in step b /, the result of the intersection between said element and a determined Voronoi cell is determined. from the point which associates it x ,, by implementing an iterative processing according to which, at a current iteration step k, an additional point x jk of the set of points other than the point x is selected, and a result is calculated an intersection of one half of the space E delimited by the mediating hyperplane of the segment (x ,, x Jk ) and containing x ,, and the result of intersection calculated at the previous iteration step,
- selection of at least one additional point in the iteration steps is a function of a comparison between the distance between the associated point x and said additional point and twice the maximum distance between the associated point x , and a point of an intersection result calculated during iterative processing.
- the invention makes it possible to reduce the volume of calculations necessary for calculating the intersections of Voronoi cells with the element under consideration, by using a test that makes it possible to avoid unnecessary calculations. It also makes it possible to parallelize the treatments for distinct Voronoi cells.
- the method according to the invention further comprises one or more of the following features:
- step b / the n-1 other points of the game arranged in order of increasing distance with respect to the point x , are denoted y , - - - x Jn 1 , and the iterative processing is implemented by selecting at the current iteration step k, the point x jk of the succeeding set of points in said increasing distance order the point x Jk 1 selected at the iteration step k-1;
- said iterative processing is stopped according to a comparison between the distance between the associated point x, and the point ik + i and the double of the maximum distance existing between the associated point x, and a point of the calculated intersection result. at the iteration step k;
- the index k is set to 1 and the intersection result is set equal to the element
- a vertex q of the updated intersection result is the intersection between the mediating hyperplane of [x ,, x p ] and an edge [qi, q 2 ] between two vertices q1, q2 of the element, where x p is a point in the set of n points;
- the coordinates of q are determined using the following formulas:
- ⁇ 2 ⁇ 1 (
- ⁇ .,.> represents the scalar product function
- a vertex q of the updated intersection result is the intersection between the mediating hyperplane of [x ,, x p ], the mediating hyperplane of [ ⁇ ,, x,], and a triangle of vertices ç q 2 , q 3 of the element, where x p and x, are two points of the set of n points;
- a 2 A " [(a 21 - 3 ⁇ 4 3)
- ⁇ 3 ⁇ "1 [(a 22 - a 21 ) II x p II 2 + (ai 1 - a 12 )
- a 21 - 2 ⁇ q 1; X
- ⁇ .,.> represents the scalar product function
- ⁇ .,.> represents the scalar product function and sign (x) is the function supplying the sign of the variable x;
- a vertex q of the updated intersection result is the intersection between the mediating hyperplane of [x ,, x p ] and an edge [qi, q 2 ] between two vertices q1, q2 of the element, where x p is a point in the set of n points;
- said vertex q of the updated intersection result is determined as the intersection between the mediating hyperplane of [x ,, x p ], the mediating hyperplane of [x ,, X
- ⁇ .,.> represents the scalar product function and sign (x) is the function providing the sign of the variable x.
- the present invention provides a data processing computer program defining an element in a space E of dimensions d, said program comprising instructions for implementing the steps of a method according to the first aspect of the present invention. invention when executing the program by processing means.
- FIG. 1 shows in part A a field of anisotropy prescribed on a 2D surface, in part B a Voronoi diagram resulting and in part C the result of the corresponding triangulation Delaunay;
- Figure 2 shows in part A an isotropic surface D, in part B a Voronoi diagram resulting and in part C the result of the corresponding triangulation of Delaunay;
- FIG. 3 partially shows a Voronoi diagram of a set of points, in part B the configuration obtained after one iteration of a Lloyd relaxation algorithm, in part C the configuration obtained after 100. iterations of a Lloyd relaxation algorithm and in part D the result of the Delaunay triangulation resulting from the configuration represented in part C;
- FIG. 4 is a view of a data processing device in one embodiment of the invention.
- FIG. 5 represents steps of a method in one embodiment of the invention.
- FIG. 6 represents steps of a method in one embodiment of the invention.
- FIG. 7 represents steps of a method in one embodiment of the invention.
- the Voronoi Vor cell (x,) associated with the point x is defined by:
- Voronoi Vor (X) diagram i.e. the abstract simplicial complex derived from the combinatorial Vor (X), is called the Delaunay triangulation.
- Delaunay's triangulation has several interesting geometric properties and is used in many applications, for example, but not only, mesh generation treatments (see Jean-Daniel Boissonnat and Mariette Yvinec, Algorithmic Geometry, Cambridge University Press, 1998). .
- a CVT can be realized by an algorithm, called Lloyd's Relaxation, which iteratively moves each point x, to the center of Vor (Xi), and provides isotropic triangles (see Stuart P. Lloyd, Least Squares Quantization in PCM, IEEE). Transactions on Information Theory, 28 (2): 129-137, 1982).
- part A (corresponding to non fat points) is shown in part A.
- the centers of Voronoi cells are in bold points.
- part B of FIG. 3 the configuration obtained after an iteration of the Lloyd relaxation algorithm is represented.
- part C of FIG. 3 the configuration obtained after 100 iterations of the Lloyd relaxation algorithm is represented.
- part D of FIG. 3 the Delaunay triangulation deduced from the configuration of part C of FIG. 3 is represented.
- S is a surface or a volume, or any other domain.
- s The Voronoi diagram of the set X restricted to S, labeled Vor (X)
- s , is the set of Voronoi Vor cells (x,), i 1 to n, restricted to S, denoted Vor (Xi)
- s Vor (x,) ⁇ S.
- s is called the restricted Delaunay triangulation. Each triangle of a restricted Delaunay triangulation corresponds to three restricted Voronoi cells with a non-empty intersection.
- restricted Voronoi cells can also be defined by Vor (Xi)
- s S ⁇ Q ⁇ (', /),
- ⁇ + (/, y) ⁇ x
- d (x, x,) ⁇ c / (x, x y ) ⁇ is the half-space in 9i d limited by l mediator hyperplane of the segment [x ,, Xj] and which contains x ,.
- One of the aspects of the invention is to make it possible to determine efficiently, among the mediating hyperplanes defined by the segments [x ,, x,], which are contributors to the Voronoi Vor cell determination (x,) and which are non-contributors. , ie Vor (x,)
- V k (Xi) be the intersection of the first k mediating hyperplanes between x, and each of these k first points, and R k its radius centered on x ,, ie:
- the safety radius theorem according to the invention is as follows:
- S0 may be a volume delimited by a surface or any other type of domain.
- the goal of the treatment is to generate an anisotropic mesh of the S0 domain according to a prescribed anisotropy field.
- a data processing device 10 shown in FIG. 4 is considered.
- Such a processing device 10 comprises a memory 1 1, a microcomputer
- a human-machine interface 13 including a display screen on which to display a mesh generated for the domain S0.
- the memory 10 notably comprises digital data defining the domain S0 and a computer program P.
- the program P includes software instructions, which when executed by the microcomputer 12, implement the steps indicated below with reference to FIGS. 5-7.
- a domain S of dimensions d> d0 is made to correspond to domain S0 of dimension d0 in accordance with the documents named references_1 above.
- d 6, or 10.
- N x , N y , N z are the normal unit vectors at the surface S0 at the point
- an iterative processing 101 is implemented to determine an isotropic mesh of the S domain.
- a step 102 the value n of the number of Voronoi cells being fixed, a set X of n points of the space 3 ⁇ 4 d , ⁇ xi, x 2 , ..., x n ⁇ with x, 6 3 ⁇ 4 d , is determined for the current iteration.
- the set X of points is for example chosen randomly.
- the set X is determined according to the results of the last iteration performed for the processing 101.
- a step 103 a step of determining the Voronoi diagram restricted to S, ie Vor (Xj)
- This loop output condition includes for example:
- the gradient standard of an "objective" function is below a certain threshold.
- the "objective" function represents the noise power of the sampling
- a restricted step Delaunay triangulation step 105 is then implemented, to determine the dual of the Voronoi diagram provided at the output of the iterative processing 101, by direct deduction of the combinatorial of the restricted Voronoi diagram, namely for each vertex of the Voronoi restricted, one generates the corresponding Delaunay triangle.
- s is carried out in the manner indicated below with reference to FIG.
- the ANN tool is used for example (David M. Mount and Sunil
- a division of the domain S into subdomains is performed, in order to be able to parallelize the steps performed on distinct subdomains (triangles, tetrahedra, etc.).
- the subdomains f of the surface S are triangles.
- the area of Vor (Xi)
- cell, associated with x, and restricted to the subdomain f, is implemented using the safety radius theorem, and considering the points x h x jn 1 ordered according to a distance X, increasing.
- step 103_4 thus comprises the following operations.
- an initialization step 103_41 consider a domain V equal to the subdomain f considered, a value t equal to 1 and a value R equal to max ⁇ d (x ,, x) / x 6V ⁇ .
- a step 103_42 the following steps are iterated as long as d (Xi, i ( ) ⁇ 2R and that t ⁇ n:
- step 103_42 is stopped.
- V is then equal to the Voronoi cell Vor (Xi)
- Sutherland &Hodgman's reentrant fenestration algorithm could be used, for example (Ivan Sutherland and Gary W. Hodgman, Reentrant Polygon Clipping, Communications of the ACM, 17: 32-42, 1974).
- the use of the safety radius theorem allows us to determine only those sections of the Voronoi cell that are useful for calculating the intersection between this cell and the considered subdomain f, thus greatly reducing the necessary computational volume. which is very appreciable especially when the value of the dimension d of the space considered increases.
- a method according to the invention implements the steps indicated below, to define the intersection between a subdomain f and a Voronoi cell, in a space of dimensions d, using the products scalars and the linear combination of vectors, the calculation volume implemented being independent of the dimension d.
- a- q is a vertex of the subdomain f considered
- b- q is the intersection between the mediating hyperplane of [x ,, x k ] and an edge [qi, q 2 ] between two vertices qi, q 2 of the subdomain f;
- c- q is the intersection between two mediating hyperplanes (for example the mediating hyperplane of [x ,, x k ] and that of [ ⁇ ,, x,], and the subdomain f; in this case, the subdomain is the triangle of vertices qi, q 2 , q 3 .
- a 21 - 2 ⁇ q 1; X
- ⁇ c 3 i + c 32 + c 33 .
- a 2 A " [(a 21 -a 23 )
- ⁇ 3 ⁇ "1 [(a 22 - a 21 ) II x k II 2 + (a! -a ⁇ )
- 2 + c 33 ]; and orient ( ⁇ (', j), q) sign ( ⁇
- the formulation of q and the orient function is therefore independent of the dimension d, in that only the scalar product ⁇ .,.> and linear combinations intervene, and where the dimension of the linear systems is independent of d.
- Recentering improves filtering performance.
- the algorithm implementing these steps of calculating the coordinates of q and the orient function is parametrized by a geometric kernel, defining the types of points and vectors, the dot product and the linear combinations of vectors. This allows to have a working implementation whatever the dimension d.
- the subdomain f is a triangle.
- the formulas indicated above are valid also for any subdomain f, for example an arbitrary polygon or any object of greater size, for example a tetrahedron (these formulas are therefore applicable in the case of a volume mesh).
- 3D reconstruction applications in particular the steps of passing from a cloud of points to a surface
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Description
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Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR1259494A FR2996669A1 (fr) | 2012-10-05 | 2012-10-05 | Procede de traitement de donnees definissant un element dans un espace e de dimensions d, programme d'ordinateur associe |
PCT/EP2013/070645 WO2014053606A2 (fr) | 2012-10-05 | 2013-10-03 | Procédé de traitement de données définissant un élément dans un espace e de dimensions d, programme d'ordinateur associé |
Publications (1)
Publication Number | Publication Date |
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EP2904587A2 true EP2904587A2 (fr) | 2015-08-12 |
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Family Applications (1)
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EP13774392.8A Withdrawn EP2904587A2 (fr) | 2012-10-05 | 2013-10-03 | Procédé de traitement de données définissant un élément dans un espace e de dimensions d, programme d'ordinateur associé |
Country Status (5)
Country | Link |
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US (1) | US10460006B2 (fr) |
EP (1) | EP2904587A2 (fr) |
CN (1) | CN104937640B (fr) |
FR (1) | FR2996669A1 (fr) |
WO (1) | WO2014053606A2 (fr) |
Families Citing this family (2)
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US11309087B2 (en) * | 2014-11-26 | 2022-04-19 | Jeffrey W. Holcomb | Method for the computation of voronoi diagrams |
CN112578082B (zh) * | 2020-12-08 | 2022-02-11 | 武汉大学 | 基于多各项同性材料各向异性同一化的处理方法 |
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CN101034482A (zh) * | 2006-03-07 | 2007-09-12 | 山东理工大学 | 复杂构件三维自适应有限元网格自动生成方法 |
FR2962582B1 (fr) | 2010-07-09 | 2013-09-27 | Inst Nat Rech Inf Automat | Dispositif d'aide a la realisation d'un maillage d'un domaine geometrique |
-
2012
- 2012-10-05 FR FR1259494A patent/FR2996669A1/fr active Pending
-
2013
- 2013-10-03 US US14/433,518 patent/US10460006B2/en active Active
- 2013-10-03 CN CN201380063103.6A patent/CN104937640B/zh active Active
- 2013-10-03 EP EP13774392.8A patent/EP2904587A2/fr not_active Withdrawn
- 2013-10-03 WO PCT/EP2013/070645 patent/WO2014053606A2/fr active Application Filing
Non-Patent Citations (2)
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Also Published As
Publication number | Publication date |
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CN104937640B (zh) | 2017-09-08 |
US20150254209A1 (en) | 2015-09-10 |
WO2014053606A2 (fr) | 2014-04-10 |
FR2996669A1 (fr) | 2014-04-11 |
CN104937640A (zh) | 2015-09-23 |
US10460006B2 (en) | 2019-10-29 |
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