阅读说明：本技术 一种鼻整形仿真方法 (Nose plastic simulation method ) 是由 葛江华 于兴泉 葛逸飞 王亚萍 尹桂宾 于 2020-07-17 设计创作，主要内容包括：本发明公布了一种鼻整形仿真方法,包括的步骤：(1)获取人脸三维点云数据,利用区域增长法将其拟合为曲面；(2)通过拟合的曲面测量鼻额角及鼻面角的角度,并求得其与公认美学标准之间的差值,得到鼻子需要增高的角度；(3)通过Bezier曲线选取鼻子需要增高的区域,确定控制点及变形点；(4)根据一种能保持细节特征的拉普拉斯网格变形方法进行变形计算,模拟鼻子整形后结果。本发明通过结合美学标准模拟鼻子整形之后的效果,能为个性化鼻子整形提供依据。(The invention discloses a nose reshaping simulation method, which comprises the following steps: (1) acquiring three-dimensional point cloud data of a human face, and fitting the data into a curved surface by using a region growing method; (2) measuring the angles of the nose frontal angle and the nose face angle through the fitted curved surface, and solving the difference between the angles and the recognized aesthetic standard to obtain the angle of the nose needing to be increased; (3) selecting an area of the nose needing to be heightened through a Bezier curve, and determining a control point and a deformation point; (4) and performing deformation calculation according to a Laplace grid deformation method capable of keeping detail characteristics, and simulating a result after nose shaping. The invention can provide a basis for personalized nose shaping by combining the aesthetic standard to simulate the effect after the nose shaping.)

1. A nose reshaping simulation method is characterized by comprising the following steps:

(1) acquiring three-dimensional point cloud data of a human face, and fitting the data into a curved surface by using a region growing method;

(2) measuring the angles of the nose frontal angle and the nose face angle through the fitted curved surface, and solving the difference value between the angles and the recognized aesthetic standard;

(3) selecting an area of the nose needing to be heightened through a Bezier curve, and determining a control point and a deformation point;

(4) and performing deformation calculation according to a Laplace grid deformation method capable of keeping detail characteristics, and simulating a result after nose shaping.

2. The method for simulating nose reshaping according to claim 1, wherein in the step (1), the region growing method is used for reconstructing the curved surface to select the nose root point as the seed point, and the points on the connecting line from the nose root to the nose tip are all the vertexes of the newly generated mesh.

3. The method for simulating nasal reshaping according to claim 2, wherein in step (2), the general frontal angle and frontal angle of the augmentation nose are considered to be large, x is the patient frontal angle and y is the patient frontal angle, so that the filling-required changing angles are:

4. the method for simulating nasal reshaping as claimed in claim 3, wherein in step (3), the vertex of the mesh where the connecting line from the root to the tip of the nose intersects in the Bezier curve is set as the control point, and the vertices in the Bezier curve other than the control point are set as the deformation points.

5. The nose shaping simulation method according to claim 4, wherein in the step (4), the deformation calculation process using the Laplace mesh deformation method comprises: and determining the representation of the Laplace coordinate differential attribute of the grid geometric information, and then obtaining the modified grid vertex coordinates under the condition of setting the control points and the deformation points, so that the deformed grid has the characteristic of keeping details.

Technical Field

The invention relates to the technical field of surgical plastic, in particular to a nose plastic simulation method.

Background

At present, the effect of the nose augmentation operation depends on the experience and technology of an operator more, the precision and the postoperative effect cannot be guaranteed, the operator cannot participate in the operation design process and predict the operation effect, and a patient may be unsatisfied with the operation effect after the operation, so that a lot of doctor-patient disputes are generated.

The demand of people for individuation is increasing day by day, and the requirements for various nose types are different. Corresponding face information is obtained by using a reverse engineering technology, an original three-dimensional model of the face is obtained by using a reconstruction technology, an operation effect satisfying doctors and patients is simulated according to basic conditions of the patients and doctor-patient communication results, then, an ideal state model is reconstructed, a basis can be provided for nose reshaping, and the nose reshaping can be repaired by using a medical means.

For the simulation of nose shaping, the most common approach is to use a simulation system based on image deformation techniques, which inputs a portrait photograph of the patient and locally stretches and distorts the image. However, two-dimensional image simulation cannot rotate the form of observing any visual angle, is not real enough in visual effect, and has little significance for operation guidance.

In order to obtain real data of three-dimensional facial morphology, the scanning image adopting the tomography CT imaging technology is most widely applied to three-dimensional reconstruction. On the basis, a spring mass point model, a finite element method and the like are often adopted for simulation. The calculated amount of the spring mass point model is relatively small, and the precision of the deformation result is poor. In addition, a few scholars have studied to deform the face surface mesh based on free deformation techniques. The FFD deformation calculation amount is small, but an additional surrounding control grid needs to be constructed, and the control grid is used for deforming the contained spatial domain, so that the operation is inconvenient.

Disclosure of Invention

The invention aims to solve the problem of providing a nose shaping simulation method aiming at the defects of the prior art.

The invention discloses a nose reshaping simulation method, which comprises the following steps of solving the technical problem:

(1) acquiring three-dimensional point cloud data of a human face, and fitting the data into a curved surface by using a region growing method;

(2) measuring the angles of the nose frontal angle and the nose face angle through the fitted curved surface, and solving the difference value between the angles and the recognized aesthetic standard;

(3) selecting an area of the nose needing to be heightened through a Bezier curve, and determining a control point and a deformation point;

(4) and performing deformation calculation according to a Laplace grid deformation method capable of keeping detail characteristics, and simulating a result after nose shaping.

In the step (1), laser scanning can be adopted to obtain human face data, and collected points often contain noise points, singular points and the like and often need to be preprocessed. The method is characterized in that a region growing method is used for fitting the curve into the curve, a nose root point is selected as a seed point by the aid of the region growing method for reconstructing the curve, points on a connecting line from the nose root to the nose tip are all newly generated grid vertexes, the newly added triangle meets the criteria that normal vectors of the two triangles are approximately parallel, the regularization maximization criterion is met, and the maximum use times of the sides are not more than 2.

In the step (2), the currently accepted beauty angle values of plastic and beauty surgeries are about 125-135 degrees of the nose frontal angle and about 36-40 degrees of the nose face angle, and the closer to the median value, the better is assumed, namely the nose frontal angle is close to 130 degrees, the nose face angle is close to 38 degrees, and the highest cushion for humping nose is 4 mm. Here, it is considered that the general nasal-frontal angle of the hump nose is large, the nasal-facial angle is small, and the patient nasal-frontal angle is x, and the nasal-facial angle is y, so the angles that need to be changed for filling are:

in the step (3), the Bzier curve can change the shape of the curve by controlling the input control vertex parameter, the grid vertex intersected by the connecting line from the root of the nose to the tip of the nose in the Bzier curve is set as a control point, the new position of the coordinate movement of the control point is the angle position to which the hump nose needs to be added, the positions except the control point in the Bzier curve are set as deformation points, and the positions except the control point in the Bzier curve are set as the deformation points, namely the coordinates of the points needing to be obtained.

In the step (4), the calculation process of the laplacian grid deformation method capable of keeping the detail features is as follows: firstly, determining a representation formula of Laplace coordinate differential attribute of the grid geometric information, and then reconstructing the modified grid vertex coordinates by using the set constraint conditions, so that the deformed grid has the characteristic of keeping details. Solving the new positions of all vertexes of the vertex set V under the Euclidean coordinate system through Laplace deformation, and concretely solving an optimization problem with position constraint, wherein an optimization equation is as follows:

Where Δ ═ LV, Δ is an n × 3 matrix, and represents the differential coordinates of n vertices; l represents a constructed Laplace matrix; v is a matrix of n multiplied by 3, expressing Euclidean coordinates of n vertexes, ui expresses a new position of a control point to be deformed and reached in an Euclidean coordinate system, i belongs to C, C expresses a set of all vertexes in a Bezier curve, and each row of V' matrix expresses a new position vector of all vertexes of a vertex set V in the Euclidean coordinate system; v' i denotes the calculated new position of the ith vertex. After the control points and the deformation points in the step (3) are determined, mature numerical calculation libraries such as SuperLU and TAUCS can be called to perform fast solving, grid coordinates after deformation are obtained, and a model after nose humping is obtained.

Compared with the prior art, the invention has the beneficial effects that: the invention adopts the Laplace deformation technology for keeping the detail characteristics, simulates the effect after nose reshaping by taking the aesthetic standard as the basis, provides a certain basis for the preparation of the nose prosthesis and the injection amount of the hyaluronic acid, and has important guiding significance for the prediction before the nose reshaping.

Drawings

Fig. 1 is a schematic flow chart of a nasal reshaping simulation method according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The flow of the nose shaping simulation method is shown in fig. 1, and the main steps are as follows: (1) acquiring three-dimensional point cloud data of a human face, and fitting the data into a curved surface by using a region growing method; (2) measuring the angles of the nose frontal angle and the nose face angle through the fitted curved surface, and solving the difference between the angles and the recognized aesthetic standard to obtain the angle of the nose needing to be increased; (3) selecting an area of the nose needing to be heightened through a Bezier curve, and determining a control point and a deformation point; (4) and performing deformation calculation according to a Laplace grid deformation method capable of keeping detail characteristics, and simulating a result after nose shaping.

The method comprises the following steps of (1) obtaining three-dimensional point cloud data of a face of a patient through a scanner, fitting the three-dimensional point cloud data into a curved surface by using a region growing method, reconstructing the curved surface by using the region growing method, selecting a nose root point as a seed point, ensuring that all points on a connecting line from the nose root to the nose tip are newly generated as a grid vertex, and ensuring that a newly added triangle meets the two triangle normal vectors which are approximately parallel and the criterion of the maximization of the regularity and the maximum using times of sides are not more than 2.

Step (2), the patient nose frontal angle is set as x, the nose face angle is set as y, so the angle needing to be filled and needing to be changed is as follows:

and (3) setting the grid vertex intersected by a connecting line from the nasal root to the nasal tip in the Bezier curve as a control point, setting the new position of the coordinate movement of the control point as the angle position to which the hump nose needs to be added, namely the angle reached by the connecting line from the nasal root to the nasal tip, setting the positions except the control point in the Bezier curve as deformation points, and setting the positions except the control point in the Bezier curve as deformation points, namely the coordinates of the points needing to be solved.

Calculating the differential coordinate of each vertex in the vertex set V: where Δ ═ LV, Δ is an n × 3 matrix, and represents the differential coordinates of n vertices; l represents a constructed Laplace matrix; v is a matrix of n multiplied by 3 and represents Euclidean coordinates of n vertexes; solving the new positions of all vertexes of the vertex set V under the Euclidean coordinate system through Laplace deformation, and concretely solving an optimization problem with position constraint, wherein an optimization equation is as follows:

wherein, Δ is a matrix of n × 3, representing the differential coordinates of n vertices; l represents a constructed Laplace matrix; v is a matrix of n multiplied by 3, expressing Euclidean coordinates of n vertexes, ui expresses a new position of a control point to be deformed and reached in an Euclidean coordinate system, i belongs to C, C expresses a set of all vertexes in a Bezier curve, and each row of V' matrix expresses a new position vector of all vertexes of a vertex set V in the Euclidean coordinate system; v' i denotes the calculated new position of the ith vertex. After the control points and the deformation points in the step (3) are determined, mature numerical calculation libraries such as SuperLU and TAUCS can be called to perform fast solving, grid coordinates after deformation are obtained, and a model after nose humping is obtained.