Method and system for modifying a 3d model of an insole based on dynamic control points

Abstract

This invention discloses a method and system for inward and outward flipping of a 3D insole model based on dynamic control point correction. The method includes: importing the 3D insole model, calculating its axial bounding box, and generating a uniformly distributed 3D control point mesh; projecting the control point mesh onto a 2D operation plane with the model's geometric center as the origin; selecting the control point set of the target deformation region by drawing a closed curve on the 2D plane and automatically determining the flipping direction; constructing a quaternion rotation matrix with the Y-axis passing through the geometric center as the rotation axis and a preset flipping angle, calculating the new coordinates of the selected control points after flipping, and generating a displacement vector; performing curvature identification and smoothing correction on the Z-axis component of this vector to obtain corrected displacement data; and applying the corrected displacement to a NURBS surface control network to complete the reconstruction of the insole surface. This invention can improve the accuracy and efficiency of inward and outward flipping of a 3D insole model.

Description

Technical Field

[0001] This application relates to the field of three-dimensional digital model processing technology, and in particular to a method and system for insole three-dimensional model inversion based on dynamic control point correction. Background Technology

[0002] In the field of digital design for footwear products, insole inversion is a crucial step in fitting the left and right feet. Traditional solutions mainly fall into two categories: geometric symmetry inversion and manual adjustment of control points.

[0003] The geometric symmetry flipping method directly mirrors the model along the sagittal plane, leading to the failure of biomechanical function in asymmetrical structures (such as the arch support area and heel cup inclination). Experimental data shows that this method produces a 12-18% pressure distribution deviation in orthotic insoles. The manual adjustment method for control points relies on designers dragging NURBS control points one by one, with a single operation taking an average of over 45 minutes, and it is difficult to maintain the continuity and smoothness of the surface.

[0004] The aforementioned existing technologies suffer from defects such as deformation distortion, low interaction efficiency, and insufficient algorithm adaptability. Deformation distortion manifests in several ways: direct rotation destroys local features, resulting in an arch collapse rate >15% and heel cup edge warping deformation of 3-5mm; the lack of Z-axis correction leads to an 8-12mm shift in the center of pressure on the sole after rotation. Low interaction efficiency is reflected in the fact that existing CAD systems require selecting control points in full 3D space, resulting in an error rate as high as 34%; and the inability to intelligently constrain the deformation range based on anatomical divisions. Insufficient algorithm adaptability is manifested in the fact that traditional Bézier surface deformation exhibits penetration in thin-walled insole structures; and linear interpolation smoothing causes abrupt curvature changes in the arch transition zone (curvature change >0.25mm). - ¹).

[0005] Therefore, how to achieve efficient and controllable insole model inversion while ensuring biomechanical accuracy is an urgent problem to be solved. Summary of the Invention

[0006] Based on this, the purpose of this invention is to address the aforementioned technical problems by providing a method and system for insole 3D model inward and outward flipping based on dynamic control point correction. This method can solve the problems of deformation distortion, low efficiency, and insufficient algorithm adaptability in traditional insole 3D model inward and outward flipping methods, and meet the high precision and low distortion design requirements of medical-grade orthopedic insoles.

[0007] To achieve the aforementioned objectives, the first aspect of this application provides a method for inward and outward flipping of a three-dimensional insole model based on dynamic control point correction, comprising:

[0008] Import the 3D model of the insole and calculate its axial bounding box, and generate a uniformly distributed 3D control point mesh based on the size of the axial bounding box;

[0009] Calculate the geometric center of the three-dimensional model of the insole and use it as the reference origin for rotational transformation;

[0010] The three-dimensional control point mesh is orthogonally projected onto the two-dimensional operation plane. Based on the closed curve drawn on the two-dimensional operation plane, the control point set of the target deformation region is selected, and the flipping direction is automatically determined according to the boundary points contained in the selected control point set.

[0011] Using the Y-axis passing through the geometric center as the rotation axis, a quaternion rotation matrix is ​​constructed according to a preset flip angle. The new coordinates of the control point set of the target deformation region after rotation are calculated, and a displacement change vector is generated.

[0012] Based on the Z-axis component of the displacement change vector, curvature identification and smoothing correction are performed to obtain the corrected Z-axis component and displacement change vector.

[0013] The corrected Z-axis component and displacement change vector are applied to the NURBS surface control network to reconstruct the surface of the insole 3D model.

[0014] Preferably, the three-dimensional control point grid has dimensions of 5×15×2, wherein the X-axis has 5 control points corresponding to the inner and outer lateral sections of the foot, the Y-axis has 15 control points matching the anatomical feature points from the heel to the forefoot, and the Z-axis has a double-layer grid for independently controlling the thickness direction of the curved surface.

[0015] Preferably, the step of automatically determining the flipping direction based on the boundary points included in the selected control point set specifically includes:

[0016] If the selected control point set contains the left boundary point with the smallest X coordinate in the three-dimensional control point grid, it is determined to trigger a counterclockwise flip.

[0017] If the selected control point set contains the right boundary point with the largest X coordinate in the three-dimensional control point grid, then a clockwise flip is triggered.

[0018] Preferably, the step of performing curvature identification and smoothing correction processing on the Z-axis component of the displacement change vector to obtain the corrected Z-axis component and the corrected displacement change vector specifically includes:

[0019] Based on Gaussian curvature, different curvature regions in the three-dimensional model of the insole are identified and divided into the arch area, heel cup area and other areas;

[0020] A piecewise cubic Hermite interpolation algorithm is used to set different cubic Hermite parameters for the arch area, heel cup area and other areas, and to perform smooth transition processing on the Z-axis component of the displacement change vector.

[0021] A tension parameter is introduced during piecewise cubic Hermitian interpolation, with the tension coefficient set to [0.4, 0.6], to preserve the original curvature characteristics;

[0022] The corrected Z-axis component and displacement change vector are calculated.

[0023] Preferably, the step of identifying different curvature regions in the three-dimensional model of the insole based on Gaussian curvature specifically involves: identifying regions with Gaussian curvature less than -0.5 as the arch region, identifying regions with Gaussian curvature greater than 0.5 as the heel cup region, and identifying regions with Gaussian curvature in the range of [-0.5, 0.5] as other regions.

[0024] Preferably, the deformation equation upon which the NURBS surface control network performs surface reconstruction is:

[0025]

[0026] Where S(u,v) is the point on the deformed surface at parameter (u,v); N i,p (u) and N j,q (v) are the p-th and q-th order B-spline basis functions in the u and v directions, respectively; P i,j These are the control points in the 3D control point mesh before Z-axis component correction; W i,j To apply to control point P i,j The deformation weighting coefficient W; i,j The distance d from the control point to the center of the user-selected target deformation area decreases exponentially.

[0027] Preferably, the deformation weighting coefficient W i,j The attenuation model is as follows:

[0028]

[0029] Where d is the distance from the control point to the center of the target deformation region.

[0030] Preferably, the method further includes a curvature compliance verification step: calculating the Gaussian curvature change of the reconstructed surface, and performing local iterative optimization on the out-of-limit region to ensure that its maximum change does not exceed a preset threshold.

[0031] To achieve the purpose of the invention, a second aspect of this application provides a system for inward and outward flipping of a three-dimensional insole model based on dynamic control point correction, applied to the inward and outward flipping method for a three-dimensional insole model based on dynamic control point correction described in the above-mentioned technical solution. The system includes:

[0032] The preprocessing module is used to import the 3D model of the insole, calculate its axial bounding box and geometric center, and generate a parametric 3D control point mesh.

[0033] The interactive processing module is used to project the three-dimensional control point mesh onto a two-dimensional plane for interactive selection of deformation areas, and automatically decide the flipping direction based on the selection result;

[0034] The deformation calculation module is used to perform quaternion spatial transformation to calculate the displacement change vector, perform biomechanical smoothing correction on the Z-axis component of the displacement change vector, and drive the NURBS surface control network to complete the surface deformation reconstruction.

[0035] Preferably, the deformation calculation module further includes:

[0036] The Z-axis correction unit is used to smooth the transition of the Z-axis component of the displacement change vector in three different curvature regions using a piecewise cubic Hermite interpolation algorithm.

[0037] The surface reconstruction unit is used to reconstruct the surface according to the deformation equation, and to perform curvature compliance verification and local iterative optimization on the reconstructed surface.

[0038] Compared with the prior art, the beneficial effects of this invention are:

[0039] This invention combines parametric control mesh generation, interactive deformation region selection, quaternion space transformation, and surface smoothing correction techniques to achieve efficient and controllable inward and outward rotation of the 3D insole model while ensuring biomechanical accuracy. This improves the accuracy and efficiency of inward and outward rotation of the 3D insole model and meets the design requirements of medical-grade orthopedic insoles. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the steps of the method of the present invention;

[0041] Figure 2 This is a schematic diagram illustrating the data flow relationship in the method of the present invention;

[0042] Figure 3 A schematic diagram showing the correspondence between the control point layout and the anatomical regions of the foot;

[0043] Figure 4 A schematic diagram illustrating the selection of the control point set for the target deformation region based on a closed curve;

[0044] Figure 5 The original rendering of the surface of the 3D model of the insole without any modifications;

[0045] Figure 6 This is a rendering of the surface of the 3D model of the insole after Z-axis Hermitian correction;

[0046] Figure 7 This is a schematic diagram of the structure of a three-dimensional insole model inward and outward flipping system based on dynamic control point correction;

[0047] Figure 8 This is a schematic diagram of the deformation calculation module. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. The following embodiments are used to illustrate the invention but are not intended to limit its scope.

[0049] Example 1

[0050] Embodiment 1 of this application provides a method for flipping the three-dimensional model of an insole inside and out based on dynamic control point correction, such as... Figure 1 As shown, it includes the following steps:

[0051] S1: Import the 3D model of the insole and calculate its axial bounding box, and generate a uniformly distributed 3D control point mesh based on the size of the axial bounding box;

[0052] S2: Calculate the geometric center of the three-dimensional model of the insole and use it as the reference origin for rotation transformation;

[0053] S3: Orthogonally project the three-dimensional control point mesh onto the two-dimensional operation plane, select the control point set of the target deformation region based on the closed curve drawn on the two-dimensional operation plane, and automatically determine the flipping direction according to the boundary points contained in the selected control point set.

[0054] S4: Using the Y-axis passing through the geometric center as the rotation axis, construct a quaternion rotation matrix according to the preset flip angle, calculate the new coordinates of the control point set of the target deformation region after flipping, and generate a displacement change vector;

[0055] S5: Perform curvature identification and smoothing correction processing on the Z-axis component of the displacement change vector to obtain the corrected Z-axis component and displacement change vector.

[0056] S6: Apply the corrected Z-axis component and displacement change vector to the NURBS surface control network to reconstruct the surface of the insole 3D model.

[0057] It should be noted that the terms "flip" and "rotate" used in this application have the same meaning.

[0058] like Figure 2 The diagram shows the data flow relationship of a method for insole 3D model inward and outward flipping based on dynamic control point correction according to the present invention. Details are as follows:

[0059] First, a 5×15×2 control point mesh is generated: This is the initial step in data processing, generating a control point mesh of a specific size. Next, the model center coordinates are calculated: Based on the generated control point mesh, the model's center coordinates are calculated. Then, interactive control point selection is performed: After calculating the center coordinates, control points are selected interactively. After interactive control point selection, the direction decision stage begins; if a left boundary point is included, a counter-clockwise rotation is performed; if a right boundary point is included, a clockwise rotation is performed. It should be noted that the dimensions of the 3D control point mesh can also be other values; the 5×15×2 dimension here is merely a preferred setting.

[0060] E / F: Indicates a counter-clockwise or clockwise rotation operation.

[0061] After the flip operation, a quaternion rotation transformation is performed: the data undergoes a quaternion rotation transformation. Next, Z-axis Hermitian smoothing correction is applied: the data in the Z-axis direction is smoothed using Hermitian smoothing to improve the smoothness and continuity of the data. Finally, NURBS surface reconstruction is performed to form a complete data flow process: the surface is reconstructed using Non-Uniform Rational B-Splines (NURBS) technology, a surface modeling technique widely used in computer graphics and CAD.

[0062] Specifically, step S1 includes:

[0063] S11. Import the 3D model of the insole (supports asymmetric insoles such as diabetic foot ulcer protective insoles, and supports multiple 3D formats: STL / OBJ / STEP), calculate the axial bounding box (AABB) of the 3D model of the insole, and obtain its vertex coordinates:

[0064] P_min = (x_min, y_min, z_min)

[0065] P_max = (x_max, y_max, z_max)

[0066] Where x_min, y_min, and z_min represent the minimum vertex coordinates of the X, Y, and Z axes of the axial bounding box, respectively, and x_max, y_max, and z_max represent the maximum vertex coordinates of the X, Y, and Z axes of the axial bounding box, respectively.

[0067] S12. Generate a uniform control point mesh with dimensions of 5 (X-axis) × 15 (Y-axis) × 2 (Z-axis) in three-dimensional space based on the axial bounding box dimensions. Wherein:

[0068] The X-axis has 5 control points corresponding to the inner and outer lateral sections of the foot; the Y-axis has 15 control points that precisely match the anatomical feature points from the heel to the forefoot; and the Z-axis has a double-layer mesh that enables independent control of the surface thickness direction.

[0069] Step S2 specifically includes:

[0070] S21. The geometric center coordinates of the axial bounding box calculation model based on the three-dimensional model of the insole in the world coordinate system. This center point serves as the reference origin for subsequent rotation transformations, ensuring that the mass distribution remains balanced during the flipping process.

[0071] Let the original point set be:

[0072]

[0073] in, P The original point set contains N three-dimensional spatial points. ; X i , Y i , Z i These are the X, Y, and Z coordinates of the i-th three-dimensional spatial point, respectively.

[0074] Computational geometry center O:

[0075]

[0076] Step S3 specifically includes:

[0077] S31. Project the control points in the control point grid onto the XY plane to generate a two-dimensional point matrix, such as... Figure 3 As shown.

[0078] S32. When drawing a B-spline closed curve, the user selects a subset of control points, such as... Figure 4 As shown.

[0079] S33. The system automatically detects whether the selected area contains boundary points:

[0080] If the left boundary point (the point with the minimum X-coordinate) is included, a counter-clockwise rotation is triggered. If the right boundary point (the point with the maximum X-coordinate) is included, a clockwise rotation is triggered. This mechanism conforms to the biomechanical principles of inversion and supination of the human foot.

[0081] Step S4 specifically includes:

[0082] S41. Constructing quaternion rotation operators (four-dimensional parameters describing spatial rotation):

[0083] Establish a local coordinate system with the geometric center as the origin, and perform local coordinate transformation:

[0084]

[0085] in, Represents local coordinates.

[0086] Given a rotation axis (Unit vector) and rotation angle θ Typically, the quaternion is defined with the Y-axis passing through the geometric center as the axis of rotation:

[0087]

[0088] Where, q w ,q x ,q y ,q z These are quaternion components, corresponding to the cosine and sine components of the rotation angle, respectively:

[0089]

[0090] Perform rotation matrix transformation (it should be noted that quaternions can be used directly or converted to a matrix according to the following formula):

[0091]

[0092] Here, R(q) represents the rotation matrix, which is obtained by quaternion transformation.

[0093] S42. Calculate the new coordinates point by point and generate the displacement change vector:

[0094] Perform coordinate transformation according to the following formula:

[0095]

[0096] in, Represents the local coordinates after rotation, which is the result of the local coordinates being transformed by the rotation matrix.

[0097] After completing the coordinate transformation, perform global coordinate restoration:

[0098]

[0099] in, Represents global coordinates, which are obtained by restoring the original spatial position from the rotated local coordinates.

[0100] Generate displacement change vector d i :

[0101]

[0102] Step S5 specifically includes:

[0103] S51. Extract control point sequence:

[0104] Sampling control point sequence along the Y-axis C :

[0105]

[0106] in, This represents the Y-axis coordinate of the k-th control point. This represents the original Z-axis coordinate of the k-th control point. This represents the Z-axis coordinate after the k-th control point has been rotated.

[0107] Then the Z-axis component of the displacement change vector of the k-th control point is:

[0108]

[0109] S52. Perform curvature identification and smoothing correction based on the Z-axis component of the displacement change vector:

[0110] Based on Gaussian curvature, different curvature regions in the 3D model of the insole are identified and divided into the arch area, heel cup area, and other areas. Regions with Gaussian curvature less than -0.5 are identified as the arch area, regions with Gaussian curvature greater than 0.5 are identified as the heel cup area, and regions with Gaussian curvature in the range of [-0.5, 0.5] are identified as other areas.

[0111] Taking a smooth transition in the arch area as an example:

[0112] set up ;y min y max These represent the minimum or maximum Y-axis coordinates of the control point sequence, respectively.

[0113] The area in the arch of the foot that needs a smooth transition is defined as follows:

[0114]

[0115] in:

[0116]

[0117] Among them, t a t b It is a coefficient that takes values ​​in the range [0, 1].

[0118] S53. Calculate the adaptive endpoint derivative:

[0119] For the starting point of the transition zone The curvature estimate of its left side (using a 3-point difference) is:

[0120]

[0121]

[0122] Transition zone start point The right-side curvature is estimated as follows:

[0123]

[0124] Then the starting point of the transition zone The adaptive derivative is:

[0125]

[0126] in, For adaptive weights.

[0127] The end point of the transition zone is calculated using the same method as the method described above for calculating the derivative at the starting point of the transition zone. derivative .

[0128] S54. Perform Hermite interpolation with tension coefficient:

[0129] Define normalization parameters:

[0130]

[0131] The tension coefficient ranges from [0.4, 0.6]. In this embodiment, the tension coefficient is set to... To maintain the original uneven features.

[0132] The corrected Hermitian basis functions are obtained:

[0133]

[0134]

[0135]

[0136]

[0137] The corrected Emil's difference formula is obtained as follows:

[0138]

[0139] in, This indicates the interpolation correction amount.

[0140] Using the modified Emil's difference formula described above, the Z-axis component of the displacement change vector in a selected area of ​​the arch region is smoothed. The smoothing correction process for the root cup region and other regions is the same as that for the arch region, only the parameter values ​​are different.

[0141] Step S6 specifically includes:

[0142] S61. Define the NURBS surface. In this embodiment, the NURBS surface is a bivariate NURBS surface:

[0143]

[0144] Where S(u,v) is the point on the deformed surface at parameter (u,v); N i,p (u) and N j,q (v) are the p-th and q-th order B-spline basis functions in the u and v directions, respectively; P i,j These are the control points in the 3D control point mesh before Z-axis component correction; W i,j To apply to control point P i,j The deformation weighting coefficient W; i,j The distance *d* from the control point to the center of the user-selected target deformation region decreases exponentially. The preferred order *p* in the U direction is 3 to ensure C... 2 The continuity of the V direction is maintained. The preferred value for the order q is 4 to accommodate the longitudinal curvature of the foot.

[0145] Deformation weighting coefficient W i,j The attenuation model is as follows:

[0146]

[0147] Where d is the distance from the control point to the center of the target deformation region.

[0148] S62. Derive the recursive formula for the B-spline basis function of a surface.

[0149] Using the Cox-de Boor recurrence relation:

[0150]

[0151]

[0152] S63. Calculate the quasi-uniform node vector of the surface.

[0153] U-direction: Let the number of control points be... Then the node vector in the U direction is:

[0154]

[0155] V direction: Let the number of control points be... Then the node vector in the V direction is:

[0156]

[0157] S64. Apply the Z-axis component correction to the deformation equation of the NURBS surface control network to the control point deformation displacement, output the corrected control points, and obtain the reconstructed 3D model surface.

[0158] Applying the Z-axis component correction to the deformation equation of the above NURBS surface control network, the control point deformation displacement is obtained:

[0159]

[0160] in, The control points before correction. This is the corresponding deformation displacement vector (Z-axis component has been corrected).

[0161] like Figure 5 The image shown is a rendering of the surface of a 3D model of an insole using the original Δz and linear interpolation. Figure 6 The image shown is a rendering of the 3D model surface of the insole after correction using Hermitian interpolation of the Z-axis component. Figure 5 compared to, Figure 6 After applying Hermite interpolation correction, significant advantages were observed in terms of surface continuity and smoothness. Visually, the corrected surface eliminated potential local fluctuations or sharp angles in the original design, presenting a more natural and fluid transition shape. The curve connections were smoother, effectively avoiding sharp turns. This improvement better conforms to the physiological curves of the foot, laying the foundation for comfort and support.

[0162] Example 2

[0163] This application's Embodiment 2, based on Embodiment 1, describes the curvature compliance verification step S7 after surface reconstruction, as follows:

[0164] Step S71: Calculate the Gaussian curvature change of the reconstructed surface.

[0165] Calculate Gaussian curvature K :

[0166]

[0167] Calculate the mean curvature H :

[0168]

[0169] Among them, the first basic form E , F , G for:

[0170]

[0171] Second basic form L, M , N for:

[0172]

[0173] The unit normal vector is:

[0174]

[0175] S72. Perform local iterative optimization on the over-limit region to ensure that its maximum change does not exceed the preset threshold.

[0176] For areas exceeding limits:

[0177]

[0178] or:

[0179] ;

[0180] Among them, K max H max The curvature threshold, determined by biomechanical constraints, is preferably 0.05 mm. -2 .

[0181] Set optimization goals:

[0182]

[0183] The out-of-limit region is subjected to iterative optimization, and the iterative steps include:

[0184] 1. Calculate the current curvature field: ;

[0185] 2. Construct the Jacobian matrix: ;

[0186] 3. Solving linear systems:

[0187]

[0188] Where λ is the regularization coefficient.

[0189] 4. Update control points:

[0190]

[0191] 5. Repeat steps 1-4 until... ,in, For iteration tolerance, the preferred value is 1e. -4 .

[0192] Example 3

[0193] This embodiment 3, based on embodiments 1 and 2, provides a system for inward and outward flipping of a 3D insole model based on dynamic control point correction. It applies the inward and outward flipping method for a 3D insole model based on dynamic control point correction described in embodiment 1. Figure 7 As shown, the system includes:

[0194] The preprocessing module 10 is used to import the 3D model of the insole, calculate its axial bounding box and geometric center, and generate a parametric 3D control point mesh.

[0195] The interactive processing module 20 is used to project the three-dimensional control point mesh onto a two-dimensional plane for interactive selection of deformation areas, and automatically decide the flipping direction based on the selection result;

[0196] The deformation calculation module 30 is used to perform quaternion spatial transformation to calculate the displacement change vector, perform biomechanical smoothing correction on the Z-axis component of the displacement change vector, and drive the NURBS surface control network to complete the surface deformation reconstruction.

[0197] like Figure 8 As shown, the deformation calculation module 30 further includes:

[0198] Z-axis correction unit 301 is used to perform smooth transition processing on the Z-axis component of the displacement change vector in three different curvature regions by using a piecewise cubic Hermite interpolation algorithm.

[0199] The surface reconstruction unit 302 is used to reconstruct the surface according to the deformation equation, and to perform curvature compliance verification and local iterative optimization on the reconstructed surface.

[0200] In summary, this invention provides a method and system for inward and outward flipping of a 3D insole model based on dynamic control point correction. By combining parametric control mesh generation, interactive deformation region selection, quaternion space transformation, and surface smoothing correction technology, it can achieve efficient and controllable inward and outward flipping of the 3D insole model while ensuring biomechanical accuracy. This improves the accuracy and efficiency of inward and outward flipping of the 3D insole model, meets the design requirements of medical-grade orthopedic insoles, and experimentally shows that the arch support curvature retention rate is >97%, the maximum deformation of the heel cup edge is reduced to below 0.8mm, the pressure center offset is controlled to <3mm, the single operation time is shortened from 45 minutes to <5 minutes, and the user interaction steps are reduced by 70%.

Claims

1. A method for inverting a 3D insole model based on dynamic control point correction, characterized in that, Includes the following steps: Import the 3D model of the insole and calculate its axial bounding box, and generate a uniformly distributed 3D control point mesh based on the size of the axial bounding box; Calculate the geometric center of the three-dimensional model of the insole and use it as the reference origin for rotational transformation; The three-dimensional control point mesh is orthogonally projected onto the two-dimensional operation plane. Based on the closed curve drawn on the two-dimensional operation plane, the control point set of the target deformation region is selected, and the flipping direction is automatically determined according to the boundary points contained in the selected control point set. Using the Y-axis passing through the geometric center as the rotation axis, a quaternion rotation matrix is ​​constructed according to a preset flip angle. The new coordinates of the control point set of the target deformation region after flipping are calculated, and a displacement change vector is generated. Based on the Z-axis component of the displacement change vector, curvature identification and smoothing correction are performed to obtain the corrected Z-axis component and displacement change vector, specifically including: Based on Gaussian curvature, different curvature regions in the three-dimensional model of the insole are identified and divided into the arch area, heel cup area and other areas; A piecewise cubic Hermite interpolation algorithm is used to set different cubic Hermite parameters for the arch area, heel cup area and other areas, and to perform smooth transition processing on the Z-axis component of the displacement change vector. A tension coefficient is introduced during piecewise cubic Hermitian interpolation, with values ​​ranging from [0.4, 0.6], to preserve the original curvature characteristics; The corrected Z-axis component and displacement change vector are calculated. The corrected Z-axis component and displacement change vector are applied to the NURBS surface control network to reconstruct the surface of the insole 3D model.

2. The method according to claim 1, characterized in that, The three-dimensional control point mesh has dimensions of 5×15×2. The X-axis has 5 control points corresponding to the inner and outer lateral sections of the foot, the Y-axis has 15 control points matching the anatomical feature points from the heel to the forefoot, and the Z-axis has a double-layer mesh for independently controlling the thickness direction of the curved surface.

3. The method according to claim 1, characterized in that, The automatic determination of the flipping direction based on the boundary points contained in the selected control point set specifically includes: If the selected control point set contains the left boundary point with the smallest X coordinate in the three-dimensional control point grid, it is determined to trigger a counterclockwise flip. If the selected control point set contains the right boundary point with the largest X coordinate in the three-dimensional control point grid, then a clockwise flip is triggered.

4. The method according to claim 1, characterized in that, The method of identifying different curvature regions in the three-dimensional model of the insole based on Gaussian curvature specifically involves: identifying regions with Gaussian curvature less than -0.5 as the arch area, regions with Gaussian curvature greater than 0.5 as the heel cup area, and regions with Gaussian curvature in the range of [-0.5, 0.5] as other regions.

5. The method according to claim 1, characterized in that, The deformation equation upon which the NURBS surface control network performs surface reconstruction is: Where S(u,v) is the point on the deformed surface at parameter (u,v); N i,p (u) and N j,q (v) are the p-th and q-th order B-spline basis functions in the u and v directions, respectively; P i,j These are the control points in the 3D control point mesh before Z-axis component correction; W i,j To apply to control point P i,j The deformation weighting coefficient W; i,j The distance d from the control point to the center of the user-selected target deformation area decreases exponentially.

6. The method according to claim 5, characterized in that, The deformation weighting coefficient W i,j The attenuation model is as follows: Where d is the distance from the control point to the center of the target deformation region.

7. The method according to claim 1, characterized in that, The method also includes a curvature compliance verification step: calculating the Gaussian curvature change of the reconstructed surface and performing local iterative optimization on the out-of-limit region to ensure that its maximum change does not exceed a preset threshold.

8. A system for insole 3D model inversion based on dynamic control point correction, employing the insole 3D model inversion method based on dynamic control point correction as described in any one of claims 1 to 7, characterized in that, The system includes: The preprocessing module is used to import the 3D model of the insole, calculate its axial bounding box and geometric center, and generate a parametric 3D control point mesh. The interactive processing module is used to project the three-dimensional control point mesh onto a two-dimensional plane for interactive selection of deformation areas, and automatically decide the flipping direction based on the selection result; The deformation calculation module is used to perform quaternion spatial transformation to calculate the displacement change vector, perform biomechanical smoothing correction on the Z-axis component of the displacement change vector, and drive the NURBS surface control network to complete the surface deformation reconstruction.

9. The system according to claim 8, characterized in that, The deformation calculation module further includes: The Z-axis correction unit is used to smooth the transition of the Z-axis component of the displacement change vector in three different curvature regions using a piecewise cubic Hermite interpolation algorithm. The surface reconstruction unit is used to reconstruct the surface according to the deformation equation, and to perform curvature compliance verification and local iterative optimization on the reconstructed surface.

Images