WO2021007935A1

WO2021007935A1 - Vr-based guide plate 3d printing model construction method

Info

Publication number: WO2021007935A1
Application number: PCT/CN2019/104404
Authority: WO
Inventors: 覃文军; 林国丛; 董智伟; 张力; 王同亮; 杨金柱; 栗伟; 曹鹏; 冯朝路; 赵大哲
Original assignee: 东北大学
Priority date: 2019-07-12
Filing date: 2019-09-04
Publication date: 2021-01-21
Also published as: CN110341192B; CN110341192A

Abstract

A VR-based guide plate 3D printing model construction method, comprising: in a virtual reality (VR) scene, cutting the plane of a cut model to obtain a cutting position and a cutting target model; performing surface grid extraction according to the grid information of the cutting target model, and generating a thin film having a preset thickness on the surface of the cutting target model; using a rectangular plate to cut the surface of the thin film at the cutting position so as to obtain the position of a guide plate clamping groove and form a guide plate surface; and according to the position of the guide plate clamping groove and a guide plate plane, constructing a guide plate 3D printing model under the VR scene. By performing modeling on the cutting position of the cut model, a guide plate and the like in the VR scene, the present invention can repeatedly perform cutting on a real surgical object multiple times in VR without limitation, and the generation of a 3D guide plate printing model at the cutting position can reduce the difficulty of the operation and the time length of manufacturing.

Description

A VR-based 3D printing model building method for guide plates

Technical field

The invention relates to the field of 3D technology, in particular to a method for establishing a 3D printing model of a guide plate based on VR.

Background technique

Compared with the traditional cutting and casting technology, 3D printing technology can not only be customized according to individual needs. For example, in the medical field, it can achieve complete matching of materials and diseased parts, perform in-situ printing of bone defect parts, and print some Free complex structures that are difficult to manufacture by traditional methods. At present, 3D printing has been successfully applied to the field of orthopedics and dentistry on a large scale. A batch of customized osteotomy guides, orthopedic implants and dental implants based on 3D printing for patients have obtained European conformity (CE) certification and the United States. Food and Drug Administration (Food and Drug Administration, referred to as FDA) approved for clinical use.

The full name of the surgical guide is the "surgical navigation physical template". It is one of the first batch of 3D printing technology's main application achievements in medical treatment. Its main function is to help accurate fracture reduction, auxiliary screws and other implants or instruments to reach predetermined positions and assist The precise cutting of the scalpel not only improves the convenience of the operation, but also significantly improves the accuracy of the operation. The use of 3D printed guide plates to assist surgery has high accuracy, reduced intraoperative risks, high surgical safety, and satisfactory clinical efficacy. It is an effective, feasible and worthy of promotion technology. However, it is necessary to print out the actual diseased part for observation, which not only wastes printing materials and printing time, but also the printed model cannot be restored after a cutting drill and needs to be printed again.

It can be seen that the prior art has problems such as large loss of printing materials and long printing time during surgical planning and pre-operative exercises.

The above-mentioned shortcomings are expected to be overcome by those skilled in the art.

Summary of the invention

(1) Technical problems to be solved

In order to solve the above-mentioned problems in the prior art, the present invention provides a VR-based guide plate 3D printing model establishment method, which solves the problems of large printing material loss and long printing time during surgical planning and pre-operative training in 3D printing in the prior art.

(2) Technical solution

In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

An embodiment of the present invention provides a VR-based 3D printing model building method of a guide plate, which includes:

In the virtual reality VR scene, the cutting position and the cutting target model are obtained based on the plane cutting of the cut model;

Performing surface mesh extraction according to the mesh information of the cutting target model, and generating a film with a preset thickness on the surface of the cutting target model;

Use a rectangular plate to cut the surface of the film at the cutting position to obtain the position of the guide plate slot and form the guide plate surface;

Constructing a 3D printing model of the guide plate in the VR scene according to the position of the guide plate slot and the guide plate plane.

In an embodiment of the present invention, the cutting position and the cutting target model obtained based on the plane cutting of the cut model includes:

Determine the cutting position and cutting plane for the cut model according to the position of the cutting tool;

The cut model is divided according to the relative position of the mesh vertex of the cut model and the cutting plane to generate model cuts, wherein the cut model is composed of a plurality of triangular faces, and the triangular faces are composed of Composed of three vertices of the grid;

The cut of the model is filled by adding a triangular mesh to form the cut target model.

In an embodiment of the present invention, the segmenting the cut model according to the relative position of the mesh vertex of the cut model and the cutting plane includes:

Establish a grid vertex array, a label array, a first vertex set and a second vertex set for storing the grid vertices according to the grid vertices, and establish an integer representing the mapping relationship between the old vertex array index and the new vertex set index Array

Transforming the mesh vertices of the cut model and a point selected on the cutting plane from space coordinates to local coordinates to obtain the local coordinates of the mesh vertices and the local coordinates of a point on the tangent plane;

Transforming the normal vector of the cutting plane from space coordinates to local coordinates to obtain a local coordinate normal vector;

The judgment is made according to the dot product of the vector formed by the local coordinates of the grid vertex and the local coordinates of a point on the tangent plane and the local coordinate normal vector. If the dot product is greater than or equal to 0, the grid The vertex is added to the first vertex set, and the corresponding label value is set in the label array; if the dot product is less than 0, the mesh vertex is added to the second vertex set , And set the corresponding tag value to 0 in the tag array.

In an embodiment of the present invention, the segmenting the cut model according to the relative position of the mesh vertex of the cut model and the cutting plane further includes:

Establishing a first triangle surface set and a second triangle surface set for storing the triangle surface for the triangle surface;

When the three mesh vertices of the triangle face are all located on one side of the cutting plane, the three mesh vertices of the triangle face are divided into the first triangle face set or the second triangle Face set

When the three mesh vertices of the triangular face are located on both sides of the cutting plane, the triangular face is cut according to the label value corresponding to the vertex index of the triangular face, and the cut triangular faces are added separately To the first set of triangles and the second set of triangles.

In an embodiment of the present invention, the cutting the triangular face according to the label value corresponding to the vertex index of the triangular face includes:

Two cutting points are formed according to the intersection of the cutting plane and the triangular surface, and the coordinate positions of the two cutting points are obtained, and the two cutting points are connected to form the boundary of the model cut;

According to the coordinate positions of the two cutting points and the original three mesh vertices of the triangles, three new triangles are formed, and the three new triangles are added to the first set of triangles and all the triangles. In the second set of triangular faces, the two cutting points are added to the first set of vertices and the second set of vertices, respectively.

In an embodiment of the present invention, said performing surface mesh extraction according to the mesh information of the cutting target model, and generating a film with a preset thickness on the surface of the cutting target model, includes:

Extracting the grid information of the cutting target model based on the spherical area grid extraction method to obtain the lower surface of the film;

Performing the displacement of the preset thickness on the lower surface of the film in the direction of the normal vector of the lower surface of the film, and searching for duplicate points on the vertices of the mesh after the displacement;

Calculate the coordinates of the displaced repeated points, and correct the displaced repeated points to the upper surface of the film based on the coordinates;

The cutting points on the edges of the upper surface of the film and the lower surface of the film are connected pair by pair to form a triangle surface to obtain the film.

In an embodiment of the present invention, the extraction of the grid information of the cutting target model based on the spherical area grid extraction method includes:

Convert the mesh vertices of the cutting target model and the selected points on the cutting plane from local coordinates to world coordinates, and calculate the mesh vertices on the cutting model and the cutting plane under the world coordinates The distance between the selected points;

Comparing the distance between the mesh vertex of the cutting target model and the cutting plane with the preset radius of the spherical region to obtain the mesh vertex in the spherical region;

According to the three vertex indexes of the triangle surface of the cutting target model, if the three vertex indexes are all in the spherical area, the triangle surface is located in the spherical area;

If the three vertex indexes are not all in the spherical area, the triangular face is cut according to the cutting plane to obtain two cutting points, which will be located between the three vertex indexes and the two cutting points. Points are generated by cutting and new triangles generated by division after cutting are divided into the spherical area;

Extract according to the mesh vertices and triangular faces in the spherical area to obtain the surface mesh in the spherical area.

In an embodiment of the present invention, the step of using a rectangular plate to cut the surface of the film at the cutting position to obtain the position of the guide plate slot and form the guide plate surface includes:

Use the rectangular plate coordinates to construct 4 planes, and respectively cut the upper surface of the film and the lower surface of the film based on the 4 planes, and the cutting position is the position of the guide plate slot;

The grid vertices of the guide plate are generated according to the apex coordinates of the rectangular plate, and the grid vertices of the guide plate are connected with the cutting points on the film to form a triangular mesh to form the surface of the guide plate.

In an embodiment of the present invention, the construction of 4 planes by using the coordinates of the rectangular plate includes:

Using the left and right sides of the rectangular plate as planes for cutting both ends of the lower surface of the film to obtain 2 planes among the 4 planes;

After the rectangular plate is translated by the preset thickness distance, it is used as a plane for cutting both ends of the upper surface of the film to obtain the remaining two planes among the four planes.

In an embodiment of the present invention, the mesh vertices of the guide plate are connected with the cutting points on the film to form a triangular mesh to form the surface of the guide plate, including:

Obtaining the cutting direction according to the coordinates of the upper and lower vertices of the rectangular plate;

Cutting the film 4 times according to the 4 planes in combination with the cutting direction to obtain an upper half circle cutting point and a lower half circle cutting point;

The upper half of the mesh vertices of the mesh vertices of the guide plate are connected with the cutting points of the upper half circle to form a triangular mesh to obtain the upper surface of the guide plate;

The lower half of the grid vertices of the grid vertices of the guide plate are connected with the cutting points of the lower half circle to form a triangular mesh to obtain the lower surface of the guide plate;

The guide plate surface is formed according to the upper surface of the guide plate and the lower surface of the guide plate.

(3) Beneficial effects

The beneficial effects of the present invention are: the VR-based guide plate 3D printing model establishment method provided by the embodiments of the present invention. On the one hand, by modeling the cutting position and guide plate of the cut model in the VR scene, it can be used in virtual reality. Repeat multiple cutting operations on the real surgical object without limitation, and generate a 3D guide plate print model at the cutting position. On the other hand, taking advantage of the realism and three-dimensionality of virtual reality, building a 3D guide plate printing model in virtual reality can reduce the operation difficulty and production time compared with the traditional direct 3D printing guide plate model.

Description of the drawings

FIG. 1 is a flowchart of a method for establishing a 3D printing model of a guide plate based on VR according to an embodiment of the present invention;

2 is a schematic diagram of a common UI interaction interface provided in an embodiment of the present invention;

3 is a schematic diagram of a UI interaction interface of a VR scene provided in an embodiment of the present invention;

4 is a schematic diagram of the UI interface in FIG. 3 according to an embodiment of the present invention;

5 is a schematic diagram of an interface for setting the tool shown in FIG. 4 in an example of the present disclosure;

Fig. 6 is a flowchart of step S110 in Fig. 1 according to an embodiment of the present invention;

FIG. 7 is a flowchart of a model cutting algorithm in an embodiment of the present invention;

FIG. 8 is a flowchart of step S120 in FIG. 1 according to an embodiment of the disclosure;

FIG. 9 is a schematic diagram of a triangle surface segmentation in an embodiment of the present invention;

10 is a schematic diagram of a cutting target model constructed in a VR scene in an embodiment of the present invention;

Fig. 11 is a schematic diagram of the guide plate model when the handle is used to lock the guide plate model in an embodiment of the present invention;

FIG. 12 is a schematic diagram of the card slot model when the handle is used to lock the card slot model in an embodiment of the present invention;

FIG. 13 is a schematic diagram of the guide plate model when the handle is used to move the guide plate model in an embodiment of the present invention;

14 is a schematic diagram of generating a double guide plate model in an embodiment of the present invention;

Figure 15 is a schematic diagram of generating a semi-guide plate model in an embodiment of the present invention.

Detailed ways

In order to better explain the present invention and facilitate understanding, the present invention will be described in detail below with reference to the accompanying drawings and through specific embodiments.

All technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the technical field of the present invention. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

In the related embodiments of the present invention, virtual reality is an emerging technology applied in the medical field in recent years, and its application in combination with traditional medical treatment also has great potential. Observe the three-dimensional model of the human bone tissue of the real patient in virtual reality, and display the complex bone condition more intuitively in front of the clinician, which is conducive to providing a clear surgical plan for the operation and avoiding the observation of the two-dimensional image. For the surgical traps found, make corresponding preparations for the extraction of the difficulties that may be encountered during the operation, which is more conducive to the determination of the surgical site and the determination of the corresponding guide plate design. Because 3D printing alone is not only a waste of printing materials and printing time, but the printed model cannot be restored after a cutting drill and needs to be printed again. In virtual reality, the real human tissue and organ model can be repeatedly cut multiple times until the optimal model solution is found, which fully reflects the advantages of virtual reality.

Fig. 1 is a flowchart of a method for establishing a 3D printing model of a guide plate based on VR according to an embodiment of the present invention. As shown in Fig. 1, the method includes the following steps:

As shown in FIG. 1, in step S110, in the virtual reality VR scene, the cutting position and the cutting target model are obtained based on the plane cutting of the cut model;

As shown in FIG. 1, in step S120, surface mesh extraction is performed according to the mesh information of the cutting target model, and a film with a preset thickness is generated on the surface of the cutting target model;

As shown in FIG. 1, in step S130, a rectangular plate is used to cut the surface of the film at the cutting position to obtain the position of the guide plate slot and form the guide plate surface;

As shown in FIG. 1, in step S140, a 3D printing model of the guide plate in the VR scene is constructed according to the position of the guide plate slot and the guide plate plane.

Based on the above, the present invention provides a VR-based 3D printing model establishment method and software system. Compared with traditional 3D printing model design software, the innovation of the present invention lies in the combination of virtual reality technology and the use of virtual reality realism and three-dimensionality. Advantages, observation and virtual surgical cutting of 3D models reconstructed 1:1 with real human tissues (such as bones), which not only effectively solves the problems of large printing material loss and long printing time during surgical planning and preoperative exercises in 3D printing. Moreover, it can automatically generate a 3D guide model of the surgical site in virtual reality, or manually perform a personalized design, which is more three-dimensional, immersive and convenient than ordinary 3D printing design software with a computer screen mouse operation, reducing the difficulty of operation And production time.

The present invention mainly includes the following three steps in specific implementation:

The first step is to construct a virtual workbench scene: construct an operating room workbench environment, and realize real-time import and export of models;

The second step is to design the UI interface suitable for the computer display screen and the virtual interactive interface in virtual reality respectively;

The third step is to construct various cutting tools, guide generation tools and design corresponding cutting algorithms and guide automatic generation algorithms.

The above three steps are described in detail below:

Step 1: Build a virtual workbench scene

In terms of scenario design, different scenarios should be designed to achieve different operational requirements. When users design 3D models, they need suitable studios, workbenches, operating tools and other scene designs. Use Unity's functional modules to perform lighting rendering of the scene, and add VR components to the scene, combining Unity's physics engine and human tissue The organ model interacts. When you need to import and export model files, you need to design a conventional computer desktop interface scene, remove VR-related components, and use the computer keyboard and mouse to operate. This is because importing model files requires operating the computer’s file explorer, while VR The operation of the handle in this respect is not as fast and convenient as the operation of ordinary keyboard and mouse input devices. Therefore, the system of the present invention designs ordinary scenes and VR scenes to meet different operation requirements. For example, users can import files in ordinary scenes. The 3D printing model of the guide plate is constructed in the VR scene.

Step 2: Design a user interface (User Interface, UI for short) for virtual interaction

In terms of UI interaction, the system designed in the present invention designs two sets of UI interfaces for common scenes and VR scenes. Figure 2 is a schematic diagram of a common UI interaction interface provided in an embodiment of the present invention. As shown in Figure 2, the common scene UI interface includes a menu option list and buttons corresponding to different functions. For example, the menu option list includes loading models and Set up and import models. Design a button to respond to mouse click events for each option, and call the file explorer to import the model file into the system in real time. By clicking the "Load Model" button, you can pop up the file explorer, select the model file and import it into the system. The model is displayed in the center of the interface. It also includes the rotation operation of the model. For example, you can select the model to rotate up and down or left and right by checking . By clicking the "reset" button, you can cancel the import model and return to the initial state; by clicking the "import model" button, confirm the import model and load the VR scene.

FIG. 3 is a schematic diagram of a VR scene UI interaction interface provided in an embodiment of the present invention. The VR scene UI needs to design a special interaction interface due to the uniqueness of the input and output device VR helmet and handle. In non-VR products, the range of the interface that can be placed is usually determined by the size of the hardware (mobile phone, computer screen). In the virtual world, it has a 360° field of view. The interface can be placed anywhere. If the interface position is fixed, the user It is likely that you need to turn around frequently to interact with the interface. If the position of the interface is not fixed, it is easy to be embedded in objects in the VR scene when the interface moves, which affects the user experience.

Therefore, the system design interface of the present invention is called up by the user clicking the handle menu button, and the interface placement position is specified by the user using the handle. When the interface is blocked by scene objects, the user can repeatedly click the menu button to reposition the interface position. This design is simple and easy to use, and users can freely adjust the position of the interface.

As shown in Figure 3, it includes the console in the foreground and the UI interface in the background. In terms of interaction with the interface, the current mainstream interaction method is to use the handle to emit rays and hover in the scene of the virtual interface. Interaction, although in this way, the user does not need to walk, nor does it need to reach out to touch the UI interface, to avoid problems such as touching the wall in reality. But the disadvantage is that the interface location needs to be far away from the user, and it is easily blocked by objects in the scene, and the ray operation does not conform to the user's behavior habits. Therefore, considering that the system interface button of the present invention is simple and the pop-up distance from the handle is relatively short, the direct contact interaction method is still adopted, which is simpler and easier to use, and conforms to the behavioral habits in reality.

The function introduction of each element of the virtual reality UI interface:

(1) Toolbar menu, click the menu button of the handle to open the toolbar. Figure 4 is a schematic diagram of the UI interface in Figure 3 of an embodiment of the present invention. As shown in Figure 4, the interface provides five operating tools for users to use. Use the handle selection key to click "Create" to generate the corresponding tools. Before the interface, click "Clear" to delete the corresponding tools in the scene in order. The 5 operating tools include:

①Cutting tool: used to cut the plane of the model imported into the system and the model generated by the system as a whole;

②Partial cutting tool: used to cut the model imported into the system and the local mesh of the model generated by the system;

③Single guide plate generation tool: Generate a rectangular plate for users to use, and use the rectangular plate to generate a corresponding size guide plate at the cutting position;

④Double guide plate generation tool: generate two rectangular plates for users to use, and use rectangular plates to generate two guide plates of corresponding size sharing a grid at the cutting position;

⑤ Semi-guide plate generation tool: Generate a rectangular plate for users to use, and use the rectangular plate to generate a single-sided guide plate of the corresponding size at the cutting position.

(2) Model operation menu, select the object to be operated, hold down the handle selection button and click the handle menu button to open the related setting menu:

Figure 5 is a schematic diagram of an interface for setting the tool shown in Figure 4 in an example of the present disclosure. As shown in Figure 5, the following settings can be made:

①Set size: You can drag the bar in the interface to change the length, width and height of the object by dragging the handle of the customs clearance. The text box on the right displays the corresponding value. Click the text box to manually enter the precise value.

②Set color: provide multiple color buttons, click the button to change the object to the color corresponding to the button, click more to change the color of the button in the interface.

③Copy object: copy the object.

④Export model: Export the model to the system folder of the present invention.

⑤Delete object: delete the selected object in the scene and close the menu interface.

The method for establishing the 3D printing model of the guide plate in the present invention is mainly implemented in the third step. Next, the specific implementation of each step shown in Figure 1 will be described in detail:

In step S110, in the virtual reality VR scene, the cutting position and the cutting target model are obtained based on the plane cutting of the cut model.

The cutting tool in this embodiment is a scalpel tool used to cut the model imported into the system and the entire model generated by the system. It can not only cut the human tissue model imported into the system, but also automatically generate the system. Trim the guide plate.

Fig. 6 is a flowchart of step S110 in Fig. 1 according to an embodiment of the present invention, which specifically includes the following steps:

In step S601, the cutting position and cutting plane for the cut model are determined according to the position of the cutting tool.

In step S602, the cut model is divided according to the relative positions of the mesh vertices of the cut model and the cutting plane to generate model cuts, wherein the cut model is composed of a plurality of triangular faces, and The triangular surface is composed of three mesh vertices.

In an embodiment of the present invention, this step includes dividing the vertices of the mesh, which specifically includes:

1) Establish a mesh vertex array, a label array, a first vertex set and a second vertex set for storing the mesh vertices according to the mesh vertices, and establish a mapping relationship between the index of the old vertex array and the index of the new vertex set An integer array of; 2) Convert the mesh vertices of the cut model and a point selected on the cutting plane from spatial coordinates to local coordinates to obtain the local coordinates of the mesh vertices and the local coordinates of a point on the tangent plane; 3 ) Convert the normal vector of the cutting plane from the space coordinate to the local coordinate to obtain the local coordinate normal vector; 4) The vector formed according to the local coordinate of the grid vertex and the local coordinate of a point on the tangent plane and the local The dot product of the coordinate normal vector is judged. If the dot product is greater than or equal to 0, the grid vertex is added to the first vertex set, and the corresponding tag value is set to 1 in the tag array 5) If the dot product is less than 0, add the grid vertices to the second set of vertices, and set the corresponding tag value to 0 in the tag array.

In an embodiment of the present invention, this step further includes dividing the triangle surface, which specifically includes:

1) Establish a first triangle face set and a second triangle face set for storing the triangle face for the triangle face; 2) When the three mesh vertices of the triangle face are all located on one side of the cutting plane When the three mesh vertices of the triangle face are divided into the first triangle face set or the second triangle face set; 3) When the three mesh vertices of the triangle face are located at all When the two sides of the cutting plane are cut, the triangle faces are cut according to the label values corresponding to the vertex indexes of the triangle faces, and the cut triangle faces are added to the first triangle face set and the second triangle respectively. Noodle collection.

In an embodiment of the present invention, in 3), cutting the triangular face according to the label value corresponding to the vertex index of the triangular face further includes:

Firstly, two cutting points are formed according to the intersection of the cutting plane and the triangular plane, and the coordinate positions of the two cutting points are obtained, and the two cutting points are connected to form the boundary of the model cut; secondly, according to the two The coordinate position of the cutting point and the original three mesh vertices of the triangular face form three new triangular faces, and the three new triangular faces are added to the first triangular face set and the second triangular face And add the two cutting points to the first vertex set and the second vertex set respectively.

In step S603, the model cut is filled by adding a triangular mesh to form the cut target model.

Based on the above, the principle of the model cutting algorithm used in step S120 is to determine a plane in space coordinates according to the position of the scalpel, and then calculate the relative position of each mesh vertex of the cut model to the plane, and establish two new vertices The array maps the grid vertices on the left and right respectively. The three triangles with all vertices on one side are assigned to the left and right triangle arrays according to the mapping relationship, and the triangles with not all vertices on one side intersect the cutting plane. After calculating the intersection points, divide these triangles and record the division The points are added to the corresponding vertex array, and finally the split points on both sides are connected to stitch the triangles, and the holes exposed by the cut objects are filled.

Fig. 7 is a flowchart of a model cutting algorithm in an embodiment of the present invention, which specifically includes the following steps:

Step S701: divide the mesh vertices on the left side of the tangent plane into group A, and divide the mesh vertices on the right side into group B;

Step S702, traverse the triangle face array;

Step S703: It is judged whether the three mesh vertices are all in the A group, if yes, then join the A group, if otherwise, go to step S704;

Step S704, judge whether the three mesh vertices are in group B, if yes, then join the group B, if not, go to step S705;

Step S705, cutting the triangular face;

Step S706, adding mesh vertices to group A or group B respectively;

Step S707, stitch the triangular faces according to the cutting points.

The following describes the segmentation of mesh vertices and triangles in step S602 with examples:

(1) Segmentation of mesh vertices

First, determine a tangent plane in world coordinates. Since the coordinates of the vertices of the cut model mesh are based on itself (that is, the local coordinate system), if the tangent plane is used to distinguish the mesh vertices, they must be in the same coordinate system, so Need to get the position information of the tangent plane in local coordinates, get a point on the tangent plane through space transformation to get the point P in local coordinates, and transform the normal vector of the tangent plane through space transformation to get the normal vector n in local coordinates, let local coordinates At any point Q(x, y, z), PQ·n=0 is the point normal equation of the plane. The following are the specific implementation steps for distinguishing mesh vertices:

(11) For the grid vertex array R[Count], create a corresponding label array B[Count], create two empty sets R1 and R2 for placing the vertices on the left and right sides, and create an array representing the index of the old vertex and the new vertex The integer array OldToNewMap[Count] of the set index mapping relationship.

(12) Each grid vertex coordinate R[i], if (R[i]-P)·n>=0, then R[i] is on the side facing the normal vector of the tangent surface, and B[i] is set to 1. , Added to the set R1, and OldToNewMap[i]=R1.Count-1; if (R[i]-P)·n<0, then R[i] is on the opposite side of the side to which the tangent normal vector faces, B [i] is set to 0, added to the set R2, and OldToNewMap[i]=R2.Count-1, thus completing the segmentation of the grid vertices.

(2) For the division of triangles

(21) For the mesh triangle array T, create two empty sets T1 and T2 for placing the left and right triangles.

(22) Traverse the triangular face array T, and take out 3 vertex indexes xi, yi, zi each time. If B[xi]=1, B[yi]=1, B[zi]=1, then the three old vertex indexes are mapped and converted to new vertex indexes and added to T1, namely: OldToNewMap[xi], OldToNewMap[yi ], OldToNewMap[zi]; if B[xi]=0, B[yi]=0, B[zi]=0, then the three old vertex indexes are mapped to the new vertex index and added to T2, namely: OldToNewMap [xi], OldToNewMap[yi], OldToNewMap[zi]; if B[xi], B[yi], B[zi] are not all 1 or not all 0, you need to cut the triangle with a tangent plane, and Add the cut triangles to T1 and T2 respectively.

(23) The key to dividing the triangular surface is to calculate the space coordinates of the cutting points M1 and M2 of the tangent surface and the triangular surface. Set B[xi]=1, B[yi]=0, B[zi]=0, M1 is The cutting point on edge R[xi]R[yi], and M2 is the cutting point on edge R[xi]R[zi]. The calculation formula is as follows:

M1=R[x _i ]+(R[y _i ]-R[x _i ])×Scalar1 (Formula 2)

Among them, Scalar1 is the ratio of the distance from M1 to R[xi] to the distance from R[yi] to R[xi]. M2 can be calculated in the same way.

(24) Add the divided new triangles R[xi], M1, M2 to T1, and add the two triangles M1, M2, R[yi] and R[yi], M2, R[zi] In T2, the cutting points M1 and M2 are added to the new vertex sets R1 and R2, so far the triangles have been divided.

After the above segmentation, the original object model grid is divided into two halves, but because the model grids are all surface grids, the interior is empty and there is no grid, so when the model is cut, the interior of the grid is exposed When it comes out, a cavity is formed, and the model with the cavity does not meet the sealing requirements of 3D printing. Therefore, it is necessary to add a triangular mesh to the model cut for stitching, as follows:

The first step is to find the vertices of the cut boundary of the model, and from the above step of cutting the mesh vertices, all the M1 and M2 cutting points generated by the cut triangles are connected to form the cut boundary of the model, so only a new one needs to be created in the cutting step Vertex set M, put all the cutting points in pairs into the new vertex set M, and then take the first cutting point in the first pair of cutting points in the set M as the reference, traverse the remaining cutting point pairs, each pair The cutting point is connected with the first cutting point to form a triangular surface, and after the traversal is completed, the cavity is filled by the triangular grid.

After the above steps, the model of the surgical guide is constructed. This part is based on the mesh information of the cut part of the human tissue model, and a certain range of film with a certain thickness is automatically generated along the surface of the tissue model. Because the film is completely with the target surface Fit, after 3D printing, it can be used as a surgical aid to support, fix, and accurately position during the operation. In addition, the doctor performs multiple cutting drills on the patient’s tissue and organ model in the VR scene to determine the cutting position during the operation. This technology can also generate diversified guide plates that are exactly the same as the cutting direction at the target cutting site, which plays a key role in the auxiliary cutting of the operation.

In step S120, surface mesh extraction is performed according to the mesh information of the cutting target model, and a film with a preset thickness is generated on the surface of the cutting target model.

In order to generate a guide plate with symmetrical, uniform thickness and settable slot length, width and height, the system of the present invention uses a standard rectangular plate in Unity to simulate the guide plate slot, and the corresponding length can be obtained by setting the length, width and height of the rectangular plate. The size of the guide plate. In this step, a certain range of surface meshes are extracted from the cutting target model, and after duplication, inversion, displacement, and edge stitching, a film with a preset thickness is obtained.

Fig. 8 is a flowchart of step S120 in Fig. 1 of an embodiment of the disclosure, which specifically includes the following steps:

In step S801, the mesh information of the cutting target model is extracted based on the spherical region mesh extraction method to obtain the lower surface of the film.

In step S802, the lower surface of the thin film is displaced by the preset thickness in the direction of the normal vector of the lower surface of the thin film, and repeated points are searched for the displaced mesh vertices.

In step S803, the coordinate after the displacement of the repeated point is calculated, and the displaced repeated point is corrected based on the coordinate to the upper surface of the film.

In step S804, the cutting points on the edges of the upper surface of the film and the lower surface of the film are connected pair by pair to form a triangle surface to obtain the film.

In an embodiment of the present invention, the extraction range of the surface grid is the range of the film. Due to the variety of actual operations and the large differences in the surgical site, there are different requirements for the size and shape of the film, no matter what extraction rule is designed It is difficult to be universally applicable to different surgical sites. Therefore, the system of the present invention adopts a unified spherical area grid extraction method, and provides cutting tools for the doctor, so that the doctor can manually adjust and modify the generated film guide to make it shape And size can meet the diverse needs of surgery.

In the above step S801, extracting the mesh information of the cutting target model based on the spherical region mesh extraction method includes:

(1) Convert the mesh vertices of the cutting target model and the selected points on the cutting plane from local coordinates to world coordinates, and calculate the mesh vertices on the cutting model and the The distance between selected points on the cutting plane;

(2) Comparing the distance between the mesh vertex of the cutting target model and the cutting plane with the preset radius of the spherical region to obtain the mesh vertex in the spherical region;

(3) According to the three vertex indexes of the triangle surface of the cutting target model, if the three vertex indexes are all in the spherical area, the triangle surface is located in the spherical area;

(4) If the three vertex indexes are not all in the spherical area, the triangular face is cut according to the cutting plane to obtain two cutting points, which will be located between the three vertex indexes and the Two cutting points are generated by cutting and new triangles generated after cutting are divided into the spherical area;

(5) Extract according to the mesh vertices and triangular faces in the spherical area to obtain the surface mesh in the spherical area.

Since the length units of different models are inconsistent, some models have length units in millimeters, and Unity’s default units are meters. Therefore, the model will be automatically scaled when importing the model, and the model grid vertex coordinate information will not change due to scaling. When extracting the grid, it is necessary to transform the coordinate information of the vertices into unified world coordinate information. The specific implementation process of the spherical area grid extraction method of the system of the present invention is as follows:

(1) Obtain the world coordinate P of the center point of the cutting board. For the local coordinate Ei of each grid vertex, the corresponding world coordinate Qi is obtained through space coordinate transformation, if |P-Qi|<radius (radius is the radius of the spherical area) , Set the corresponding label of Qi to 1, otherwise it is 0. When the label is 1, put Ei into the new vertex array V, let the i-th vertex of the array E be the j-th vertex of the new array V, create an array oldToNewMap to record the index mapping relationship Ei=Vj, the normal vector of the grid vertex The same is true.

(2) Traverse the array of triangles. For the three vertices index Top, L, R of each triangle, if the corresponding labels of the three vertices are all 1, then the triangle is in the spherical area, and the index of the triangle is passed The oldToNewMap map is converted to the new mesh vertex index and then loaded into the new triangle array T; if the labels of the three vertices are all 0, no operation is performed outside the extraction range; if some vertices are 1 and some are 0, This shows that the triangle is at the extraction boundary. If it is simply discarded or loaded, it will cause the edge of the film to appear jagged, which is not conducive to 3D printing and practical use. Therefore, the next step is to divide the triangle with the spherical area boundary.

(3) The cases where the labels are not all 1 are divided into the following two types: 1) When there is a vertex with a label of 1, and two vertices with a label of 0, it means that a corner of the triangle mesh is in the extraction area. The cut triangle is enough; 2) When the label of two vertices is 1, and the label of one vertex is 0, then the extracted area is an irregular rectangle, which needs to be connected diagonally to obtain two triangular faces (LS, R ,L)(R,LS,RS) is added to the new triangle array. Figure 9 is a schematic diagram of the triangular face segmentation in an embodiment of the present invention. As shown in Figure 9, the single vertex in the area is Top, the outside of the area is L and R, and the cutting points generated by cutting are LS and RS. Solve the following equations to calculate the coordinate value of LS. RS is the same. Taking LS as an example, the calculation formula is as follows:

LS=L+(Top-L)·x (Formula 3)

|LS-P|=radius (Formula 4)

(4) After adding the new vertices and triangular faces produced by cutting to the new mesh, the surface mesh in the spherical area is successfully extracted.

After the surface mesh is extracted in the previous step, the surface mesh needs to be replicated to produce a film with a preset thickness. A mesh model without thickness cannot be 3D printed. The specific steps for producing the film are as follows:

(1) Calculate each element of the new vertex array V and the vertex normal vector array N obtained in the above steps to obtain the corresponding new vertex coordinates and normal vector:

v=V _i +N _i ·Thickness (Equation 5)

n=N _i (Equation 6)

Thickness is the thickness of the film, which can be regarded as a new layer of mesh obtained after each vertex of the mesh is displaced in the direction of its normal vector by Thickness units. This new layer of mesh will be used as the upper surface of the film, the original mesh As the bottom surface of the film.

It should be noted that there is often a type of vertices in the model mesh. The coordinates of these vertices are the same but the normal vectors are different. The appearance of this kind of vertices is to fit the sharp parts of the surface of the object, such as the corners of a cube. The point actually has 3 vertices at the same position, each with 3 different normal vectors. When the method of step (1) is used to translate these vertices, the original vertices at the same position will separate, causing the model mesh to break, so Special treatment is required for such duplicate points. The specific processing method is: first find out the duplicate points, because the number of duplicate points is not consistent with each other, so the set ArrayList structure is used to store the duplicate points; then each set of duplicate points is nested into the record how many sets of duplicate points In the ArrayList collection, finally calculate the coordinates of each set of repeated points after displacement:

Where Count is the number of repeated points, Rate is the ratio of the average normal vector of the repeated points to the normal vector of the new point, and vi is the coordinate of any point in the repeated point. Use the calculated coordinate v to correct the displaced repeated point to Solve the problem of grid cracking on the upper surface.

It should also be noted that in step (1) to use the original mesh as the lower surface mesh, it is necessary to reverse the order of the normal vector and the triangle face index, reverse the normal vectors of the original mesh vertices one by one, and reverse the triangle Surface data is fine.

(2) After obtaining the upper and lower mesh surfaces, the edges of the two layers need to be sewn together, and the film forms a closed model, which meets the necessary conditions for 3D printing. Stitching needs to record all the cutting points that have been cut on the boundary triangle when extracting the mesh. These cutting points form the edges of the two-layer mesh surface. Find the upper and lower surface edge cutting points to connect the triangles one by one to complete the stitching. Obtain a film.

In step S130, a rectangular plate is used to cut the surface of the film at the cutting position to obtain the position of the guide plate slot and form the guide plate surface.

In an embodiment of the present invention, this step specifically includes:

First, four planes are constructed using the rectangular plate coordinates, and the upper surface of the film and the lower surface of the film are respectively cut based on the four planes, and the position of the cutting is the position of the guide plate slot. The way to obtain four planes is to use the left and right sides of the rectangular plate as the planes for cutting both ends of the lower surface of the film to obtain two of the four planes; translate the rectangular plate to the preset After the thickness distance, the two ends of the upper surface of the film are cut as planes to obtain the remaining two planes among the four planes.

Secondly, the grid vertices of the guide plate are generated according to the coordinates of the vertices of the rectangular plate, and the grid vertices of the guide plate are connected with the cutting points on the film to form a triangular mesh to form the surface of the guide plate.

Based on the above, in this step, the coordinate information of the rectangular plate is used to construct 4 planes, and the upper and lower surfaces of the film are cut twice to remove the grid in the middle part. The free part is the position of the card slot. Finally, according to the rectangular plate The vertex coordinates of the generated guide plate are connected with the cutting points of the film to be cut to construct a triangular mesh to form the surface of the guide plate. This step includes: 1) Obtain the cutting direction according to the coordinates of the upper and lower vertices of the rectangular plate; combine the cutting direction to cut the film 4 times according to the 4 planes to obtain the upper half circle cutting point and the lower half Circle cutting points; 2) The upper half of the mesh vertices of the grid vertices of the guide plate are connected with the upper half circle cutting points to form a triangular mesh to obtain the upper surface of the guide plate; 3) The grid vertices of the guide plate The vertices of the bottom half of the grid in the bottom half are connected with the cutting points of the bottom half circle to form a triangular mesh to obtain the lower surface of the guide plate; 4) The guide plate surface is formed according to the upper surface of the guide plate and the lower surface of the guide plate.

Therefore, in order to generate the grid of the guide plate on the film in this step, the middle part of the film needs to be cut to free the position of the guide plate. The inner surface of the guide plate is connected with the lower surface of the film, and the outer surface of the guide plate is connected with the upper surface of the film. Since the guide plate itself also has thickness, that is, the inner and outer surfaces need to be staggered, the system of the present invention selects the left and right sides of the rectangular plate as the planes at both ends of the lower surface of the cutting film, and translates the two sides by the thickness distance left and right as the upper surface of the cutting film. The plane at both ends. The principle of cutting is basically the same as the above model cutting algorithm, and the part about cutting will not be repeated here.

In this step, 4 planes that cut the two ends of the upper and lower surface grids are generated respectively. The specific steps are as follows:

(1) Select 3 vertices A1, A2, A3 with different coordinates on the left side of the rectangular plate;

(2) Construct vectors A1A2 and A1A3, then the plane normal vector n=A1A2×A1A3, get the point normal equation of the plane from A1, n, and the right plane is constructed in the same way;

(3) The cutting plane of the upper surface on the left side can be obtained by the translation of the cutting plane of the lower surface, that is, take the point B1=A1+n·Thickness, and the normal vector is the same as n, then the plane equation for cutting the upper surface on the left side can be obtained. Reasonable.

Secondly, find the upper and lower half circle cutting points of each cutting. After the 4 cuttings facing the film in the above steps, there is a section in the middle of the film grid. To generate the key guide plate grid, you need to find out separately The upper and lower half circle cutting points of 4 cuts, the specific steps are as follows:

(1) First calculate the cutting direction cutVector of the guide plate assisted cutting. The cutting direction can be obtained by the coordinates A1 and A2 of the upper and lower vertices of the rectangular plate: cutVector=A2-A1;

(2) Obtain the normal vector n of the plane that cuts the film grid, and then create a vector thwartwiseNormal=cutVector×n, use this vector to find the leftmost point and the rightmost point among all cutting points, for each cutting point Ci, calculate its corresponding value

Value[i]=(C _i -Point)·thwartwiseNormal (Formula 8)

Where Point is any point in the cutting plane, Ci corresponding to the minimum value of Value[i] is the rightmost cutting point, and Ci corresponding to the maximum value of Value[i] is the leftmost cutting point;

(3) After finding the left and right edge points, find the adjacent cutting points clockwise, start from the two points respectively, find the other side to stop, you can find the upper and lower half circle cutting points, and put them into the corresponding set. Since each triangle is divided, two cutting points will be generated, which are put into the new vertex array as a pair of cutting points, so one of the pair of cutting points of each triangle has the same coordinates as the cutting point of the adjacent triangle. According to this principle, starting from the leftmost point, traverse the cutting point array. If it finds a cutting point that matches itself, put another point of the cutting point group into the array and continue to search for the matching point at this point until the most The right point terminates the loop, the cutting point saved in the array is the cutting point of the upper half circle, and the cutting point of the lower half circle can be obtained in the same way.

(4) Calculate the apex of the guide plate, the apex of the upper part of the guide plate is connected with the cutting point of the upper half circle, and the apex of the lower part of the guide plate is connected with the cutting point of the lower half circle.

In step S140, a 3D printing model of the guide plate in the VR scene is constructed according to the position of the guide plate slot and the guide plate plane.

In this embodiment, a single guide plate and cut human tissue as a bone model is taken as an example, and the model is simulated by cutting tools and a variety of guide plate generation tools to obtain the surgical auxiliary guide plate corresponding to the cutting position. FIG. 10 is the present invention A schematic diagram of a cutting target model constructed in a VR scene in an embodiment. Figures 11 to 13 are schematic diagrams of a process of automatically generating a single guide model in a VR scene in an embodiment of the present invention. Figure 11 is an embodiment of the present invention. Fig. 12 is a schematic diagram of locking the card slot model with the handle in an embodiment of the present invention, and Fig. 13 is a schematic diagram of using the handle to move the guide plate model in an embodiment of the present invention.

It should be noted that there are diversified requirements for the shape of the guide plate in different surgical scenes. In addition to a single guide plate with a closed card slot, some parts require a semi-guide plate with an unclosed card slot, and some parts require two card slots. The closed guide plates are connected to the same film, so the system of the present invention provides multiple styles of guide plate generation methods on the basis of a single guide plate, which are packaged in a guide plate generation tool for users to choose and use. The following briefly introduces the changes of different style guides to the above algorithm:

(1) Double guide plate style: The system of the present invention provides two rectangular plates for users to use, which respectively represent the position of the two-cut guide plate. After the first guide plate is generated, only the grid generated by the first guide plate, the upper and lower Information such as the surface grid is transferred to the second guide plate, and the second guide plate executes the guide plate generation method again on the basis of the first generated film. FIG. 14 is a schematic diagram of generating a double guide plate model in an embodiment of the present invention.

(2) Semi-guide plate style: The surface grid extraction and film generation steps of the semi-guide plate generation are the same as those of ordinary guide plates, but when the film grid is cut, 4 planes are no longer used for cutting, but 2 planes are used to cut one side The grid on the other side is directly discarded. Therefore, there are some differences in detail between the vertices of the guide plate and the connection between the vertices of the guide plate and the cutting point. The grid vertices on both sides of the single guide plate are connected to form a triangular surface , The guide plate with only one side is formed to obtain the semi-guide plate. FIG. 15 is a schematic diagram of generating the semi-guide plate model in an embodiment of the present invention.

It should also be noted that in addition to the diversified requirements for the shape of the guide plate, there are different requirements for the width, length, height of the guide plate slot and the angle of the slot guiding cutting. In order to meet the design of the personalized guide plate, all the guide plates The length, width, height and angle of the slot are determined by the corresponding guide plate generation tool, so you can open the object operation menu by selecting the tool, and customize the guide plate generation tool in the menu setting size to change the generated guide plate. Value, and the angle of slot-guided cutting is determined by the angle at which the user places the tool. After the guide plate is generated, you can also use a cutting tool to trim the guide plate to remove excess parts, so as to facilitate the export of the guide plate model for 3D printing and then use it directly.

In summary, the above method provided by the embodiments of the present invention, on the one hand, by modeling the cutting position, guide plate, etc. of the cut model in the VR scene, the real surgical object can be unrestricted in virtual reality. Repeat the cutting operation several times to generate a 3D guide plate print model at the cutting position. On the other hand, taking advantage of the realism and three-dimensionality of virtual reality, building a 3D guide plate printing model in virtual reality can reduce the operation difficulty and production time compared with the traditional direct 3D printing guide plate model.

It should be noted that although several modules or units of the device for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiments of the present invention, the features and functions of two or more modules or units described above may be embodied in one module or unit. Conversely, the features and functions of a module or unit described above can be further divided into multiple modules or units to be embodied.

Through the description of the above embodiments, those skilled in the art can easily understand that the example embodiments described here can be implemented by software, or by combining software with necessary hardware. Therefore, the technical solution according to the embodiments of the present invention can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, U disk, mobile hard disk, etc.) or on the network , Including several instructions to make a computing device (which may be a personal computer, a server, a touch terminal, or a network device, etc.) execute the method according to the embodiment of the present invention.

After considering the specification and practicing the invention disclosed herein, those skilled in the art will easily think of other embodiments of the present invention. This application is intended to cover any variations, uses, or adaptive changes of the present invention. These variations, uses, or adaptive changes follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not disclosed by the present invention. . The description and the embodiments are to be regarded as exemplary only, and the true scope and spirit of the present invention are pointed out by the following claims.

It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

A VR-based method for establishing a 3D printing model of a guide plate is characterized in that it includes:

In the virtual reality VR scene, the cutting position and the cutting target model are obtained based on the plane cutting of the cut model;

Performing surface mesh extraction according to the mesh information of the cutting target model, and generating a film with a preset thickness on the surface of the cutting target model;

Use a rectangular plate to cut the surface of the film at the cutting position to obtain the position of the guide plate slot and form the guide plate surface;

Constructing a 3D printing model of the guide plate in the VR scene according to the position of the guide plate slot and the guide plate plane.
The method for establishing a 3D printing model of a guide plate based on VR according to claim 1, wherein the obtaining the cutting position and the cutting target model based on the plane cutting of the cut model comprises:

Determine the cutting position and cutting plane for the cut model according to the position of the cutting tool;

The cut model is divided according to the relative position of the mesh vertex of the cut model and the cutting plane to generate model cuts, wherein the cut model is composed of a plurality of triangular faces, and the triangular faces are composed of Composed of three vertices of the grid;

The cut of the model is filled by adding a triangular mesh to form the cut target model.
The method for establishing a 3D printing model of a guide plate based on VR according to claim 2, wherein the segmenting the cut model according to the relative position of the mesh vertex of the cut model and the cutting plane comprises :

Establish a grid vertex array, a label array, a first vertex set and a second vertex set for storing the grid vertices according to the grid vertices, and establish an integer representing the mapping relationship between the old vertex array index and the new vertex set index Array

Transforming the mesh vertices of the cut model and a point selected on the cutting plane from spatial coordinates to local coordinates to obtain the local coordinates of the mesh vertices and the local coordinates of a point on the tangent plane;

Transforming the normal vector of the cutting plane from space coordinates to local coordinates to obtain a local coordinate normal vector;

The judgment is made according to the dot product of the vector formed by the local coordinates of the grid vertex and the local coordinates of a point on the tangent plane and the local coordinate normal vector. If the dot product is greater than or equal to 0, the grid The vertex is added to the first vertex set, and the corresponding label value is set in the label array; if the dot product is less than 0, the mesh vertex is added to the second vertex set , And set the corresponding tag value to 0 in the tag array.
The VR-based guide plate 3D printing model establishment method of claim 3, wherein the cut model is divided according to the relative position of the mesh vertex of the cut model and the cutting plane. include:

Establishing a first triangle surface set and a second triangle surface set for storing the triangle surface for the triangle surface;

When the three mesh vertices of the triangle face are all located on one side of the cutting plane, the three mesh vertices of the triangle face are divided into the first triangle face set or the second triangle Face set

When the three mesh vertices of the triangular face are located on both sides of the cutting plane, the triangular face is cut according to the label value corresponding to the vertex index of the triangular face, and the cut triangular faces are added separately To the first set of triangles and the second set of triangles.
The method for establishing a 3D printing model of a guide plate based on VR according to claim 4, wherein the cutting the triangular face according to the label value corresponding to the vertex index of the triangular face comprises:

Two cutting points are formed according to the intersection of the cutting plane and the triangular surface, and the coordinate positions of the two cutting points are obtained, and the two cutting points are connected to form the boundary of the model cut;

According to the coordinate positions of the two cutting points and the original three mesh vertices of the triangles, three new triangles are formed, and the three new triangles are added to the first set of triangles and all the triangles. In the second set of triangular faces, the two cutting points are added to the first set of vertices and the second set of vertices, respectively.
The VR-based guide plate 3D printing model establishment method of claim 2, wherein the surface mesh extraction is performed according to the mesh information of the cutting target model, and the surface of the cutting target model is generated on the surface of the cutting target model. Set the thickness of the film, including:

Extracting the grid information of the cutting target model based on the spherical area grid extraction method to obtain the lower surface of the film;

Performing the displacement of the preset thickness on the lower surface of the film in the direction of the normal vector of the lower surface of the film, and searching for duplicate points on the vertices of the mesh after the displacement;

Calculate the coordinates of the displaced repeated points, and correct the displaced repeated points to the upper surface of the film based on the coordinates;

The cutting points on the edges of the upper surface of the film and the lower surface of the film are connected pair by pair to form a triangle surface to obtain the film.
8. The VR-based 3D printing model building method of a guide plate according to claim 6, wherein the extraction method based on the spherical area grid extracting the grid information of the cutting target model comprises:

Convert the mesh vertices of the cutting target model and the selected points on the cutting plane from local coordinates to world coordinates, and calculate the mesh vertices on the cutting model and the cutting plane under the world coordinates The distance between the selected points;

Comparing the distance between the mesh vertex of the cutting target model and the cutting plane with the preset radius of the spherical region to obtain the mesh vertex in the spherical region;

According to the three vertex indexes of the triangle surface of the cutting target model, if the three vertex indexes are all in the spherical area, the triangle surface is located in the spherical area;

If the three vertex indexes are not all in the spherical area, the triangular face is cut according to the cutting plane to obtain two cutting points, which will be located between the three vertex indexes and the two cutting points. Points are generated by cutting and new triangles generated by division after cutting are divided into the spherical area;

Extraction is performed according to the mesh vertices and triangular faces in the spherical area to obtain the surface mesh in the spherical area.
The VR-based 3D printing model building method of a guide plate according to claim 1, wherein the rectangular plate is used to cut the surface of the film at the cutting position to obtain the position of the guide plate slot and form the guide plate surface ,include:

Use the rectangular plate coordinates to construct 4 planes, and respectively cut the upper surface of the film and the lower surface of the film based on the 4 planes, and the cutting position is the position of the guide plate slot;

The grid vertices of the guide plate are generated according to the apex coordinates of the rectangular plate, and the grid vertices of the guide plate are connected with the cutting points on the film to form a triangular mesh to form the surface of the guide plate.
The method for establishing a 3D printing model of a guide plate based on VR according to claim 8, wherein said constructing 4 planes by using the coordinates of the rectangular plate comprises:

Using the left and right sides of the rectangular plate as planes for cutting both ends of the lower surface of the film to obtain 2 planes among the 4 planes;

After the rectangular plate is translated by the preset thickness distance, it is used as a plane for cutting both ends of the upper surface of the film to obtain the remaining two planes among the four planes.
The VR-based 3D printing model building method of a guide plate according to claim 8, wherein the grid vertices of the guide plate are connected with the cutting points on the film to form a triangular mesh to form the guide plate Surface, including:

Obtaining the cutting direction according to the coordinates of the upper and lower vertices of the rectangular plate;

Cutting the film 4 times according to the 4 planes in combination with the cutting direction to obtain an upper half circle cutting point and a lower half circle cutting point;

The upper half of the mesh vertices of the mesh vertices of the guide plate are connected with the cutting points of the upper half circle to form a triangular mesh to obtain the upper surface of the guide plate;

The lower half of the grid vertices of the grid vertices of the guide plate are connected with the cutting points of the lower half circle to form a triangular mesh to obtain the lower surface of the guide plate;

The guide plate surface is formed according to the upper surface of the guide plate and the lower surface of the guide plate.