Method for functional modeling of a relief element present in a three-dimensional surface, electronic device implementing said method

Abstract

Method (10) for functional modeling of a relief element (3) present in a surface, comprising the following steps: - acquisition (11) of a three-dimensional image of said surface, this image being in the form of a point cloud describing this surface; - selection (12) of a plurality of points from the point cloud marking a target relief element joining said selected points, this target relief element extending between a first selected point and a second selected point; - extraction (13) from the point cloud of a sub-point cloud around the target relief element, this sub-point cloud describing a sub-surface; - modeling (14) of the sub-surface by means of a free-form surface; - determination (15), from a model of the sub-surface, of a first topographic line of the sub-surface;- determination (16) of a second topographic line and a third topographic line on either side of the first line. Figure to be published with the abstract: Fig 2;

Description

Title of the invention: Method for functional modeling of a relief element present in a three-dimensional surface, electronic device implementing said method

[0001] The present invention relates to methods for functional modeling of a relief element included in a three-dimensional surface, as well as to computer program products for adapting electronic devices so that the latter implement such methods.

[0002] A "relief feature" means a linear groove or protrusion present on a three-dimensional surface. A groove means any linear depression, linear depression, fold or groove present on the surface of an object such as a skin furrow, a nasolabial fold, a crease, a wrinkle, a fine line, or a notch in skin, a crack or split in a material or a trench or fault in a ground. As for the term "linear protrusion", it refers to any elevation, protuberance or, more generally, any local deformation where a portion of the surface extends above the surrounding level along a line such as a suture line, a varicose vein or scar in skin, a weld line or ribs on the surface of a manufactured part or a wave on the surface of water.A relief element can be natural, intentionally created for various functional or aesthetic reasons, or resulting from stress, wear, or other factors.

[0003] Methods for detecting and modeling relief elements present on the surface of a real object are known from the state of the art. However, these methods are limited to a digital representation of the appearance in space, i.e. to three-dimensional (3D) geometric characteristics, of the relief elements. Such a static representation does not allow the dynamic behavior of a relief element to be properly studied.

[0004] An object of the present invention is to provide one or more functional models of a relief element, in other words models which go beyond a simple static 3D geometric representation in order to simulate the behavior, operation and / or interactions of this relief element in a virtual environment.

[0005] Another object of the present invention is to produce a functional three-dimensional model, namely a geometric model whose use is not limited to visualization but also allows the measurement, mechanical simulation and dynamic evaluation of a relief element.

[0006] Firstly, a method of functional modeling of a relief element present in a surface, this method comprising the following steps - acquisition of a three-dimensional image of said surface, this image being presented in the form of a point cloud describing this surface; - selecting a plurality of points from the point cloud marking a target relief element joining said selected points, this target relief element extending between a first selected point and a second selected point of said plurality of selected points; - extraction of the point cloud from a sub-point cloud around the target relief element, this sub-point cloud describing a sub-surface of said surface; - modeling of the subsurface using a free-form surface parameterized using control points; - determination, from a model of the subsurface, of a first topographic line of the subsurface joining the first selected point and the second selected point; - determination, from the subsurface model, of a second topographic line and a third topographic line on either side of the first topographic line.

[0007] Various additional features may be provided, alone or in combination: - the relief element is a furrow; - the first topographic line is a bottom line of the furrow; - the relief element is a linear projection; - the first topographic line is a ridge line of the linear projection; - the deformable surface is a uniform cubic B-Spline surface; - the initial shape of the freeform surface is chosen based on business data; - the surface is initialized by a lattice of control points included in a plane integrating the first selected point and the second selected point; - the step of determining the second topographic line comprises a search for a change in slope, relative to an axis perpendicular to the longitudinal direction of the target relief element, between a first substantially rectilinear segment and a second successive substantially rectilinear segment of the sub-surface starting from the first topographic line.

[0008] Secondly, a computer program product is proposed which is implemented on a storage medium and which can be implemented within a processing unit of an electronic device and which comprises instructions for implementing implementation of the process presented above.

[0009] The invention further relates to a computer-readable storage medium comprising the instructions of such a computer program product.

[0010] The invention relates to an electronic device comprising: - a processing unit; - a data memory; - a program memory comprising the program instructions of such a computer program product.

[0011] Other characteristics and advantages of the invention will appear more clearly and concretely on reading the following description of embodiments, which is given with reference to the appended drawings in which:

[0012] [Fig-1] schematically illustrates a surface comprising a relief element according to various embodiments;

[0013] [Fig.2] schematically illustrates steps of a functional modeling process tional of a relief element present in a surface according to various embodiments;

[0014] [Fig.3] schematically illustrates a sub-cloud of points extracted from a cloud of points describing said surface;

[0015] [Fig.4] schematically illustrates a free-form surface according to various modes of realization ;

[0016] [Fig.5] schematically illustrates topographic lines characterizing an element in relief according to various embodiments;

[0017] [Fig.6] illustrates an electronic device suitable for implementing a method according to the invention.

[0018] [Fig.l] illustrates an illustrative example of a three-dimensional or 3D image 1. Such an image is that of a body area, in this case a human face, comprising one or more cutaneous relief elements 3 such as a wrinkle. Alternatively, such an image could describe a fine line, a scar, a varicose vein, a suture line of any other part of a human body. Such an image 1 could be that of a shell comprising a crack, a weld line or a bonding line in connection with a physical object.

[0019] In connection with [Fig.l], [Fig.2] presents a method 10 for functional modeling of a relief element present in a 3D surface according to the invention, said method 10 being intended to be implemented by a processing unit of an electronic device such as a smart mobile phone, a portable or fixed computer. Such a method 10 comprises a first step 11 of acquiring a three-dimensional image of said surface using capture means of said electronic device or cooperating with the latter. This step 11 ultimately consists of producing a image in the form of a cloud 2 of points describing this captured surface. [Fig.l] illustrates such a cloud 2 of points assembled into a volume of points which represents the topology of the surface to be studied. Each point of this cloud 2 of points is represented by coordinates or by distance data and a solid angle in a predefined (absolute or relative) three-dimensional reference frame. This reference frame is most often associated with the device for taking the 3D image 1 such as a 3D camera, a depth camera, a photogrammetry device or a 3D scanner (laser scanner, Lidar, stereoscopic scanner, modulated light scanner or silhouette scanner for example). Of course, attributes or data associated with each point of the cloud 2 of points can, in addition, include other information directly from the captured image, such as light intensity, color or grayscale information.The invention further provides that said step 11 comprises a processing consisting of analyzing such a captured image to deduce therefrom semantic information or “business knowledge” and thus enrich the attributes or data associated with the points of the cloud 2. Such an analysis thus makes it possible to identify the physical body or an area of ​​said body on which the image capture relates (whether said body is a human, animal, plant or mineral body, or even a material object, to determine physical properties (for example, physical properties specific to a tissue, an organ, a bone or a muscle for a biological material or body), and / or biomechanical properties (for example, rigidity, elasticity, toughness, viscoelasticity or compressive strength, etc.) and thus produce complementary attributes associated with the points of the cloud 2 of points.Such processing may rely on shape recognition or object identification techniques advantageously but not limited to implementing “Machine Learning” techniques or more broadly any automatic learning techniques based on mathematical and statistical approaches to give a computer the ability to “learn” from data, without being explicitly programmed on purpose. Such processing may also rely on one or more models of capturable surfaces (or skins), models translating such physical and biomechanical properties according to the nature of said surfaces, to produce said complementary attributes mentioned above or on inputs or entries from the user of the electronic device implementing the method 10. .

[0020] The latter comprises a selection step 12, according to which a plurality of points 21-22 of the cloud 2 of points is selected to mark a target relief element 30 joining said selected points 21-22. This target relief element 30 extends between a first selected point 21 and a second selected point 22 of said plurality of selected points 21-22. These points 21-22 are, for example, selected in a 3D view using a selection means such as a computer mouse or equivalent. This is an initial marking of the relief element 3 to be modeled to designate its approximate position on the surface described by the point cloud 2.

[0021] In one embodiment, the target relief element 30 is marked only by a first and a second selected point 21-22 representing the two ends of this target relief element 30 having the shape of a segment. Alternatively, a plurality of intermediate selected points 21-22 (in particular, two or three) can be envisaged to mark a curved target relief element 30.

[0022] The selection of points 21-22 by an operator (for example, a medical practitioner or a technician) advantageously makes it possible to recover professional knowledge. In this case, the selected points 21-22 marking the two ends of the target relief element 30 are considered to be precisely acquired. In one embodiment, the “professional knowledge” comprises characteristics of the anatomical structure studied.

[0023] In connection with [Fig. 3], as illustrated in said [Fig. 3], a sub-cloud 20 of points around the target relief element 30 is extracted from the cloud 2 of points during an extraction step 13, this sub-cloud 20 of points describing a sub-surface of the initial surface. The sub-cloud 20 of points integrates, for example, the points of the cloud 2 of points located less than a predefined distance around the target relief element 30. The sub-cloud 20 of points is therefore associated with a sub-surface local to the groove or to the linear projection.

[0024] As indicated in said [Fig. 3], a three-dimensional Cartesian reference frame R(Ox, Oy, Oz) is associated with the extracted sub-cloud 20 so that the two end points 21, 22 of the target relief element 30 are on the Oy axis at equal distance from the center O of the reference frame. In other words, the two ends of the target relief element 30 are centered on the origin of the Cartesian reference frame on the Oy axis (i.e. located on the Oy axis symmetrically on either side of the origin O of the reference frame R). The origin O of the reference frame is placed in the middle of the segment joining the two ends of the target relief element 30, as illustrated in [Fig. 4]. These two ends have coordinates (0, -yO, 0) and (0, yO, 0) where -yO and yO are respectively the ordinate of the first and second points 21, 22 selected delimiting the target relief element 30. In addition, the plane xOy is chosen so that the projection onto this plane of the sub-cloud 20 of points is maximum.Indeed, a rotation around the Oy axis is applied to the sub-cloud 20 of points or, equivalently, to the R(0x, Oy, Oz) reference frame, until the projection onto the xOy plane of the sub-surface described by the sub-cloud 20 of points is maximum. This sub-surface is therefore as close as possible to the xOy plane and its shape is mainly described by elevations and / or depressions along the Oz axis.

[0025] Such an arrangement of the reference frame R(0x, Oy, Oz) advantageously places it “flat” on the xOy plane the sub-cloud 20 of points of interest, the Oz axis giving the height / depth of the target relief element 30. This step aims, in particular, to focus the following steps on the sub-surface of interest around the target relief element 30 to be modeled. Since these are isometries applied to the sub-cloud 20 of points, it is possible to return to the initial reference frame associated with the cloud 2 of points with inverse transformations, the measurement calculations being identical in both reference frames.

[0026] In connection with Figures 2 and 4, during a modeling step 14 of a method 10 according to the invention, the sub-surface described by the sub-cloud 20 of points is modeled by means of a free-form surface 23 (continuous and derivable) of the B-Spline surface type, a NURBS surface (Non Uniform Rational Basis Splines), a Bézier surface, or a T-Spline surface. As indicated in [Fig. 4], the free-form surface 23 is parameterized using control points 24. The modeling step 14 iteratively adjusts the free-form surface 23 until it represents the sub-cloud 20 of points by passing through it sufficiently closely to erase artifacts while highlighting its shape characteristics. The adjustment of the free-form surface 23 is carried out by moving its control points 24.

[0027] Indeed, referring to [Fig.4], an iterative algorithm makes it possible to refine the matching of the control points 24 of the free-form surface 23 with the sub-surface described by the sub-cloud 20 of points, by minimizing the distance which separates them. This algorithm implements an iterative registration method to bring the free-form surface 23 into coincidence with the sub-surface described by the sub-cloud 20 of points, by moving one or more control points 24 of the free-form surface 23.

[0028] In one embodiment, the free-form surface 23 is a uniform cubic B-Spline surface. Advantageously, a uniform cubic B-Spline surface makes it possible to reproduce local variations in shape while maintaining a level of continuity and derivability consistent with the surface to be modeled. In one embodiment, a uniform cubic B-Spline surface is associated with a local lattice of sixteen control points 24 (4x4), this local lattice being a part of a global lattice of NxM control points 24 which covers the sub-surface described by the sub-cloud 20 of points to be modeled. The displacement of a control point 24 produces a deformation of the free-form surface 23 on the four neighboring tiles of order one and the twelve neighboring tiles of order two (the deformations on the twelve neighboring tiles of order two being quite small compared to those applied to the four neighboring tiles of order one).

[0029] In one embodiment, a free-form surface 23 is first initialized by a lattice of NxM control points 24 arranged regularly in the plane xOy (i.e. their z coordinate is 0) and comprising the segment joining the two ends on the Oy axis of the target relief element 30. More generally, the free-form surface 23 is initialized by a lattice of control points 24 included in a plane integrating the first selected point 21 and the second selected point 22.

[0030] Then, for each control point 24, a displacement D along the Oz direction maximizing a predefined proximity criterion of the four neighboring tiles to the points of the sub-cloud 20 of points that they cover is determined. The proximity criterion is, for example, the sum of the squares of the distances (along the Oz direction) of the points of the sub-cloud 20 to the free-form surface 23. The control point 24 whose displacement D would be the largest (i.e. the most distant from the sub-surface described by the sub-cloud of points) is moved by the distance D. These last two steps can be repeated as long as the predefined proximity criterion is greater than a predefined threshold value. This advantageously results in a surface model, for example of the B-Spline type, adjusted to the sub-surface described by the sub-cloud 20 of points.This model is defined by one or more parametric functions of the free surface, depending on the final position of the control points 24.

[0031] The control points 24 form elementary surface tiles (or “patches”) making it possible to highlight and eliminate noise and artifacts (aberrant points in the sub-cloud 20 of points), to locally represent the sub-cloud 20 of points by a smooth surface and with controlled precision, and to recalibrate data and / or integrate new data.

[0032] In another embodiment, the initial shape of the free-form surface 23 is chosen based on business data, in particular the geometric or anatomical structure of the point sub-cloud 20 (for example, the relationships between the phalanges of a hand or those between the elements of a face, the physiological constraints on these components, the mechanical properties of all the muscles and tendons, as well as the skin, the existence of visible furrows or veins), making it possible to accelerate the convergence of the above steps for modeling the point sub-cloud 20 and improve its accuracy. A free-form surface 23 whose initial geometry is similar to that of the target point sub-cloud 20 advantageously makes it possible to reduce the number of iterations of the aforementioned modeling steps.Advantageously, business data indicating representative points of the subsurface to be modeled also makes it possible to reduce any noise included in the position data of the points of the sub-cloud 20 of points.

[0033] In connection with [Fig.2] and as illustrated by [Fig.5], from the obtained model of the sub-surface, the method 10 comprises a step 15 of determining a first topographic line 31 of said sub-surface joining the first selected point 21 and the second selected point 22. This first topographic line 31 corresponds, in fact, to a bottom line (in the case of a furrow) or a ridge line (in the case of a linear projection) of the target relief element 30. The first topographic line is constrained at the two selected ends. The first selected point 21 and the second selected point 21 constitute two predefined passage points of the first topographic line 31.

[0034] The first topographic line 31 joining the selected points 21, 22 can be visualized as a broken line (Spline of degree one) or as a “soft” line (Spline of degree three). This first topographic line 31 constitutes a first snap line of a model describing / reproducing the bottom line or the crest line of the target relief element 30. Starting from an initial broken line joining the points 21, 22 selected beforehand, said step 15 consists of sampling this broken line uniformly along the Oy axis, when the number of points 21-22 selected is less than a predefined value (for example, 10). In other words, by having a broken line defined by the selected points 21-22 approximating the first topographic line 31, a new broken line comprising more points or, more generally, a predefined number of points depending on the application, is determined.This sampling advantageously makes it possible to have a sufficient number of intermediate points between the two ends of the target relief element 30.

[0035] In one embodiment, the first topographic line 31 is determined using a constrained elastic model; that is, a broken line joining two fixed points (the two ends of the relief element 30) and capable of deforming until it matches the bottom line of a furrow or the crest line of a linear projection to the extent of a maximum elastic stress.

[0036] For each intermediate point (whether selected or added by sampling, except for the ends), a local extremum on the subsurface around this intermediate point is searched for, namely the lowest point (in the case of a groove) or the highest point (in the case of a linear protrusion) in an immediate vicinity of said intermediate point (for example, within a predefined distance of said intermediate point). This local extremum replaces the corresponding intermediate point. This search for local extremums is iterated as long as the length of the first topographic line 31 is less than a predefined proportion of the initial length of the first initial topographic line or as long as the difference between two successive lengths of the first topographic line 31 is less than a predefined threshold (for example, 2% or 5%).The line thus determined is used as a support for a cubic Spline curve which characterizes the first topographic line 31 of the subsurface described by the sub-cloud 20 of points.

[0037] A second topographic line 32 and a third topographic line 33 on either side of the first topographic line 31 are also determined, in a step 16 of the method 10, from the model of the sub-surface described by the sub-cloud 20 of points. The second topographic line 32 and the third topographic line 33 correspond to the edges of the target relief element 30 on either side of the first topographic line 31.

[0038] The two edge lines are, in one embodiment, determined by evolving a plane parallel to the xOy plane in the direction of the Oz axis. For this, step 16 consists of evolving vertically a horizontal plane (i.e., for which z is constant) and keeping the line of intersection of this plane with the sub-surface which is closest or, more generally, which is located less than a predefined distance from the first topographic line 31. Professional knowledge can, advantageously, be used to define said predefined distance according to the envisaged application (for example, the detection of wrinkles / fine lines, cracks / slits or the detection of varicose veins / reticular varicose veins.)

[0039] In another embodiment, the two edge lines of the relief element are detected by looking for a "break point" on the subsurface in a direction perpendicular to the longitudinal direction of the relief element. This break point marks a change in slope relative to the Oz axis (or any other axis perpendicular to the longitudinal direction of the target relief element 30) between a first substantially rectilinear segment and a second successive substantially rectilinear segment (the first segment and the second segment being joined at this break point) of the subsurface starting from the first topographic line 31.

[0040] The break point is detectable approximately on the "rounding" of the passage from the inside to the outside of the relief element. Taking a first point A of the bottom / ridge of the relief element and a second point B outside the relief element in the direction of the axis Ox, the break point C is the point joining two substantially rectilinear sections AC and CB.

[0041] For example, when the first topographic line 31 is composed of a plurality of points (for example 10 points) intermediate between the first selected point 21 and the second selected point 22, step 16 then consists of implementing the following process for each of said intermediate points: - sampling the intersection of the subsurface with the xOy plane passing through said intermediate point; - searching for the first change of direction (for example, using a vector product of the successive sampling points) greater than a predefined threshold in the two sections on either side of said intermediate point to detect, respectively, a first break point included in the first edge line and a second break point included in the second edge line.

[0042] Advantageously, any of the embodiments described above for the detection of edge lines can be adopted depending on the morphology of the relief element and the intended use of the functional modeling of this relief element (for example, the envisaged medical application of the functional modeling of a wrinkle).

[0043] The method 10 thus makes it possible to have a free-form model constrained at the two selected ends of the target relief element 30 and three lines (bottom or ridge line and the two edge lines). An additional optimization step of the model obtained can be envisaged by repeating the previous optimization step, but by considering the topographic lines 31-33 determined as constraints to be respected. Such a step makes it possible to improve the reliability and robustness of the three-dimensional model.

[0044] This advantageously results in a model allowing all simulations and measurements on an area of ​​interest of the surface studied. It is, for example, possible to recover various descriptors of the relief element such as its length, its curvature, the variation of its width, its depth or its height over its length, its volume, its possible deformations taking into account the mechanical (or biomechanical) properties of the surface, its possible reactions to predefined actions (injection of product, tensions, pressures for example).

[0045] When it comes to a skin surface (for example, the surface of a face), the embodiments described above advantageously allow an exhaustive characterization of the human skin relief (for example, a characterization of wrinkles or a scar according to numerous geometric criteria such as for example length, width, depth, volume, or curvature) so as to be able to more easily search for a suitable treatment, to follow over time or to evaluate the success of an intervention or the effectiveness of a treatment (a care product for example).

[0046] This functional three-dimensional modeling includes information on how the relief element behaves or interacts with its environment or in response to a predefined action. For this, the functional three-dimensional model obtained advantageously integrates mechanical parameters related to the biomechanical study of the anatomical structure studied.

[0047] Advantageously, the embodiments presented above, including in particular those of the modeling of the sub-surface by means of a free-form surface, make it possible to integrate data of different modalities, of different resolutions, and not geometrically realigned in space, to eliminate noise and artifacts and to control the precision with which the results are produced.

[0048] As indicated in [Fig.6], an electronic device 100 arranged to implement a method according to the invention (as described in connection with [Fig.2]) comprises a central processing unit 111 (in the form of one or more micro processors or microcontrollers) controlling, by signals carried by a communication bus symbolized in [Fig.6] by double arrows in single lines, electronic elements including a memory. The latter comprises a data memory 112 and a program memory 113, said memories 112 and 113 being able to form a single physical entity. The term "memory" means any computer memory whether volatile or not. A non-volatile memory is a computer memory whose technology retains its data in the absence of an electrical power supply. It can contain data resulting from entries, calculations, measurements and / or program instructions.The main non-volatile memories currently available are electrically writable such as EPROM technology ("Erasable Programmable Read-Only Memory") or electrically writable and erasable such as EEPROM technology ("Electrically-Erasable Programmable Read-Only Memory"), flash, SSD ("Solid-State Drive"), etc. Non-volatile memories are distinguished from so-called "volatile" memories, the data of which is lost in the absence of a power supply.The main volatile memories currently available use RAM (Random Access Memory), DRAM (dynamic random access memory, requiring regular updating), SRAM (static random access memory requiring such updating during a power shortage), DPRAM or VRAM (particularly suitable for video), etc. An electronic device 100 may further comprise one or more matrix image sensors 114 in the form of a depth camera (or a 3D camera). Such an electronic device 100 may comprise means of communication 115 with the outside world in the form of an input unit and an output unit. To operate, such an electronic device 100 generally comprises an electrical energy source 116, external or internal in the form of one or more batteries for example.The processing unit 111 may also comprise means 117 for controlling an input and / or output human-machine interface. The term "output human-machine interface" means any means, used alone or in combination, making it possible to output or deliver a graphic, haptic, sound or, more generally, human-perceptible representation. Such an output human-machine interface may consist, in a non-exhaustive manner, of one or more screens, speakers or other suitable alternative means. The term "input human-machine interface" means a computer keyboard, a pointing device, a touch screen, a microphone or, more generally, any interface arranged to translate a gesture or an instruction issued by a human into control or configuration data. Avanta . Conveniently, the input and output human-machine interfaces may constitute a single physical entity.

[0049] Such an electronic device 100 may consist of a smart mobile phone (or "smartphone" according to English terminology), an electronic tablet, a desktop or laptop computer. The arrangement of the functional modeling method according to the invention, such as to be able to be implemented by such a device 100 that we could qualify as "general public", allows the exploitation of non-specific or specialized capture means for the implementation of the invention. Such a device 100, for example a smartphone, may be adapted by loading into its program memory 113 a computer program P comprising instructions to cause, during their execution, the implementation of a method according to the invention.This computer program P may use any programming language, and may be in the form of source codes, object codes, or intermediate codes between source codes and object codes, such as in an interpreted, partially or fully compiled form, or in any other desirable form.

Claims

Claims

1. Method (10) for functional modeling of a relief element (3) present in a surface (1), this method (10) being intended to be implemented by a processing unit (111) of an electronic device (100) and comprising the following steps: - acquisition (11) of a three-dimensional image (1) of said surface, this image being in the form of a cloud (2) of points describing this surface; - selection (12) of a plurality of points (21-22) of the cloud of points marking a target relief element (30) joining said selected points (21-22), this target relief element (30) extending between a first selected point (21) and a second selected point (22) of said plurality of selected points; - extraction (13) from the cloud (2) of points of a sub-cloud (20) of points (21-22) around the target relief element (30), this sub-cloud of points describing a sub-surface of said surface;- modeling (14) of the subsurface by means of a free-form surface (23) parameterized using control points (24); - determining (15), from a model of the subsurface, a first topographic line (31) of the subsurface joining the first selected point (21) and the second selected point (22); - determining (16), from the model of the subsurface, a second topographic line (32) and a third topographic line (33) on either side of the first topographic line (31).;

2. Method (10) according to the preceding claim, characterized in that the relief element (3) is a groove.

3. Method (10) according to the preceding claim, characterized in that the first topographic line (31) is a bottom line of the furrow.

4. Method (10) according to claim 1, characterized in that the relief element (3) is a linear projection.

5. Method (10) according to the preceding claim, characterized in that the first topographic line (31) is a ridge line of the linear projection.

6. A method (10) according to any preceding claim, characterized in that the freeform surface (23) is a uniform cubic B-Spline surface.

7. Method (10) according to any one of the preceding claims, characterized in that the initial shape of the free-form surface (23) is chosen according to business data.

8. Method (10) according to any one of claims 1 to 6, characterized in that the surface (23) is initialized by a lattice of control points (24) included in a plane integrating the first selected point (21) and the second selected point (22).

9. Method (10) according to any one of the preceding claims, characterized in that the step of determining (16) the second topographic line (32) comprises a search for a change in slope, relative to an axis perpendicular to the longitudinal direction of the target relief element (30), between a first substantially rectilinear segment and a second successive substantially rectilinear segment of the sub-surface starting from the first topographic line (31).

10. Electronic device (100) comprising: - a processing unit (111); - a data memory (112); - a program memory (113); said electronic device being characterized in that the processing unit (111) is arranged to implement a method (10) for functional modeling of a relief element (3) present in a surface (1) according to any one of the preceding claims.

11. Computer program product (P) implemented on a memory medium, capable of being implemented within a computer processing unit and comprising instructions for implementing a method for functional modeling of a relief element present in a surface according to any one of claims 1 to Q

12. y. Computer-readable storage medium comprising the instructions of a computer program product according to the preceding claim.

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