Method for obtaining variable radius point array structure slice data based on line segment set intersection approximation

Abstract

The application relates to a variable-radius dot matrix structure direct slicing based on line segment set intersection approximation and belongs to the technical field of dot matrix structure geometric model slicing. The application represents a circular truncated cone as a line segment set and uses the intersection of the line segment and a plane to approximate a slicing result, avoids the situation that an analytical solution cannot be obtained when a plane and a circular truncated cone equation are solved simultaneously in a traditional method, can provide a more definite solution, and thus improves the stability and accuracy of slicing. The application adopts the same solving process for equal-radius and variable-radius rods, avoids the complexity of classifying and discussing different types of rods in the traditional method, significantly simplifies the calculation logic, and speeds up the whole solving process. Through the approximation strategy based on the line segment set and the pixel merging processing mode, the application realizes efficient and high-precision slicing of a complex dot matrix structure, improves the slicing generation efficiency, and ensures consistent processing of different rod types.

Description

Technical Field

[0001] The present invention relates to the technical field of slicing geometric models of lattice structures, and specifically to a method for direct slicing of variable-radius lattice structures based on intersection approximation of line segment sets, and more particularly to slicing geometric models of lattice structures, wherein the output data information is used for manufacturing by an additive manufacturing machine. Background Art

[0002] A lattice structure is a porous structure composed of nodes and rods connected and arranged in three-dimensional space. Due to its excellent specific strength and topological properties, it is widely used in high-end customized fields such as aerospace and biomedical devices, and is typically processed using additive manufacturing technology. To achieve additive manufacturing, corresponding slicing data must be provided for the lattice structure. Currently, there are two main technical routes for generating lattice structure slicing data: Technical Route 1: STL Model-Based Slicing This route uses an STL (StereoLithography) triangular facet model as a starting point and generates slicing data by slicing the STL model layer by layer. Specifically, the 3D geometric model of the lattice structure is represented in the form of triangular facets. Multiple slicing planes are then generated in space. By intersecting the 3D model with these planes, a series of 2D cross-sectional contour lines are obtained, which can be recognized and processed by additive manufacturing equipment. This method relies on the mature STL format and the slicing algorithms it supports. It is suitable for processing complex geometric models. However, because STL files are based on mesh descriptions, they suffer from data redundancy and low accuracy. Technical Route 2: Direct Slicing Based on Geometric Information This route directly uses the geometric information and topological relationships of the lattice structure to generate slice data, without relying on the intermediate triangular facet representation. By analyzing the node positions and rod connection information of the lattice structure, the geometric cross-sectional profiles of the nodes and rods of each layer can be directly determined during the slicing process, thereby generating the slice data required for additive manufacturing equipment. This method avoids the data redundancy and precision loss caused by the STL format, can generate slice data more efficiently, and improves the accuracy of expressing structural details. It is particularly suitable for customized design and high-precision manufacturing scenarios with special requirements for nodes and rods.

[0003] In the prior art, there are at least the following technical problems in generating slice data of a lattice structure:

[0004] Question 1: Disadvantages of STL-based model slicing

[0005] The existing technical route for slicing based on STL models has several obvious flaws. This method is based on the use of triangular facets to represent the geometric shape of the lattice structure, and this representation method is prone to data redundancy and loss of precision when describing complex lattice structures. Since the STL format can only approximate the geometric shape of the model through the number and fineness of triangular facets, the complex thin rods and node features in the lattice structure require a large number of facets to accurately represent, which in turn leads to two major technical problems: first, the model file is very large, resulting in increased storage and processing costs; second, the model inevitably faces a loss of geometric accuracy during the slicing process, especially in the representation of subtle features, which can easily lead to inaccurate slicing data, thereby affecting the final quality of additive manufacturing. In addition, the method of performing plane intersection operations on the STL model layer by layer has a large amount of computation and low processing efficiency. In particular, when the lattice structure contains a large number of rods and nodes, the slicing time increases significantly.

[0006] Problem 2: Disadvantages of Direct Slicing Based on Geometric Information

[0007] Although the technical route of directly generating slice data based on geometric information overcomes the data redundancy and precision loss problems brought by the STL model, there are still technical difficulties in the existing implementation methods. First, the direct generation of slice data requires accurate analysis of the geometric information and topological relationships of the lattice structure. The current direct slicing algorithm is difficult to directly slice lattice structures with variable radius. When using methods such as functional equation parameterization and precise calculation for direct slicing, problems such as the inability to find analytical solutions will be encountered. Secondly, the current direct slicing algorithm based on geometric information often faces the problem of high computing resource consumption when parsing the topological relationships of complex lattice structures. In particular, when dealing with lattice structures containing a large number of nodes and rods of different scales, it is easy to cause a significant increase in calculation time, affecting slicing efficiency.

[0008] To sum up, the shortcomings of the existing technology mainly include: the slicing method based on the STL model faces the problems of data redundancy, loss of geometric accuracy and low processing efficiency; while the technical route of direct slicing based on geometric information has shortcomings in algorithm complexity and computing resource consumption, and is difficult to handle lattice structures with variable radius, and is difficult to adapt to the efficient analysis and functional customization requirements of complex lattice structures. Summary of the Invention

[0009] In view of the above problems, the present invention provides a method for obtaining slicing data of a variable-radius lattice structure based on line segment set intersection approximation. Through the approximation strategy based on line segment sets and the pixel processing method, efficient and high-precision slicing of complex lattice structures is achieved, which not only improves the efficiency of slice generation, but also ensures consistent processing of different rod types, and has significant practicality and application promotion value. It can achieve efficient slicing of variable-radius lattice structures, and has the characteristics of controllable precision, and directly generates the slicing data required for additive manufacturing.

[0010] The present invention provides a method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation, comprising:

[0011] Step S1, setting a node set and a rod set of a geometric model; constructing a lattice structure of the geometric model based on the node set and the rod set; the rod set includes a plurality of rods; each rod represents a connection relationship between nodes;

[0012] Analyzing geometric information of the lattice structure of the geometric model to obtain a plurality of geometric information; each geometric information includes the three-dimensional coordinates of each node and the starting point coordinates and the end point coordinates of each rod;

[0013] Uniformly slice the geometric model lattice structure along the z-axis to obtain multi-layer slice planes;

[0014] Step S2: let e=1. When e=1, it represents the first rod; when n=1, it represents the nth slice plane;

[0015] Convert the e-th rod into a corresponding frustum; the frustum is a set of line segments; the upper and lower radii of the frustum are equal or unequal;

[0016] Obtain the starting point coordinates and ending point coordinates of each line segment in the line segment set based on the starting point coordinates and ending point coordinates of the e-th rod;

[0017] Step S3, obtaining the layer height of the nth slice plane;

[0018] Establishing a parametric equation for the intersection of each line segment with the nth slice plane using the starting and ending coordinates of each line segment in the line segment set corresponding to the eth member and the layer height of the nth slice plane; solving the parametric equation for the intersection of each line segment with the slice plane to obtain the intersection point of each line segment in the eth member with the nth slice plane;

[0019] It can be understood that the layer height of the nth slice plane is the height difference between the slice planes of each layer; preferably, the expression of the parametric equation of each line segment and the nth slice plane is:

[0020] z1+t(z2-z1)=z k ,0≤t≤1

[0021] Among them, t is the intersection parameter of the line segment and the plane. If t is [0,1], it means that the line segment intersects the plane, z k is the position of the slice plane, z1 is the starting coordinate of the z-axis coordinate of the line segment, and z2 is the ending coordinate of the z-axis coordinate of the line segment.

[0022] Step S4: Fit the intersection points of each line segment in step S3 with the n-th slice plane to generate a contour projection of the e-th rod on the n-th slice plane. Convert the contour projection of the e-th rod on the n-th slice plane into a two-dimensional pixel image based on manufacturing accuracy and discretization requirements to obtain a two-dimensional pixel image of the e-th rod on the n-th slice plane.

[0023] Preferably, in step S4, the projection of the outline of the e-th rod on the n-th slice plane is the minimum circumscribed rectangle of the geometric outline, which is expressed as:

[0024] AABB e，n ={(x min，e，n ,y min，e，n ), (x max，e，n ,y max，e，n )}

[0025] Among them, AABB e，n is the minimum circumscribed rectangle of the geometric outline of the projection of the outline of the e-th member on the n-th slice plane, that is, the axis-aligned bounding box; min，e，n is the minimum value of the projection of the contour of the e-th member on the n-th slice plane in the x-axis direction, y min，e，n is the minimum value of the projection of the contour of the e-th member on the n-th slice plane in the y-axis direction; x max，e，n is the maximum value of the contour projection of the e-th member on the n-th slice plane in the x-axis direction; y max，e，n is the maximum value of the contour projection of the e-th member on the n-th slice plane in the y-axis direction.

[0026] Preferably, the expression of the two-dimensional pixel image of the e-th rod on the n-th slice plane in step S4 is:

[0027]

[0028]

[0029] Among them, u e，n v is the x-axis coordinate of the two-dimensional pixel image of the e-th rod on the n-th slice plane; e，n is the y-axis coordinate of the two-dimensional pixel image of the e-th rod on the n-th slice plane; e，nis the x-axis coordinate of the mapped point of the e-th member in the original contour diagram on the n-th slice plane; e，n is the y-axis coordinate of the mapped point of the e-th member in the original contour image on the n-th slice plane;

[0030] W is the width of the pixel image, and H is the height of the pixel image.

[0031] Step S5: Determine whether n is greater than or equal to N, where N represents the total number of slice planes. If so, obtain a two-dimensional pixel map of the line segment set corresponding to the e-th member on each slice plane and proceed to the next step; if not, set n = n + 1 and return to step S3;

[0032] Step S6: Determine whether e is greater than or equal to E. If so, obtain a two-dimensional pixel map of each slice plane corresponding to the line segment set of each rod in the lattice structure, that is, a two-dimensional pixel map of each slice plane; if not, set e=e+1 and return to step S3;

[0033] Step S7: combining the two-dimensional pixel images in each slice plane into complete slice data by using Boolean and Boolean addition methods to obtain slice data of each slice plane;

[0034] Preferably, the expression of the slice data of each slice plane in step S7 is:

[0035]

[0036] Among them, P final,n (x, y) is the x-axis coordinate and y-axis coordinate of the n-th slice plane; P n (x,y) is the x-axis coordinate and y-axis coordinate of the n-th slice plane.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] (1) The present invention achieves high-precision and efficient slicing of variable-radius lattice structures through an approximate approach that is higher than the manufacturing accuracy;

[0039] (2) The present invention represents the frustum as a set of line segments and uses the intersection of line segments and planes to approximate the slicing results. This avoids the problem of being unable to obtain an analytical solution when solving the plane and frustum equations simultaneously in traditional methods, and can provide a clearer solution, thereby improving the stability and accuracy of slicing.

[0040] (3) The present invention uses the same solution process for rods of constant radius and variable radius, avoiding the complexity of classifying and discussing different types of rods in traditional methods, significantly simplifying the calculation logic and speeding up the entire solution process;

[0041] (4) The present application can flexibly control the approximation accuracy of the slice profile by changing the number of line segment sets, thereby balancing the use of computing resources under the condition of meeting the manufacturing requirements, and the adjustable accuracy control effectively improves the adaptability of the method, and meets different requirements for accuracy in different manufacturing scenarios;

[0042] (5) The present application can effectively avoid the process of additional calculation of the entire outer contour by performing Boolean merging on the rod section pixel map of each layer, ensure the generation speed of the slice data, reduce the additional complexity that may be introduced by the traditional outer contour calculation, and at the same time ensure the integrity and consistency of the final slice result, thereby further improving the calculation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0043] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated herein and constitute a part of this application.

[0044] Figure 1 A flowchart for obtaining dot matrix structure slice data in an embodiment of the present application;

[0045] Figure 2 A system structure schematic diagram for obtaining dot matrix structure slice data in an embodiment of the present application;

[0046] Figure 3 A schematic diagram for approximating a truncated cone using a line segment set and then intersecting a plane to obtain an intersection point set in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of intersecting rods in different layer slice planes and slice data in an embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict. In addition, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0049] One specific embodiment of the present application, as Figure 1-4 , discloses a method for obtaining variable radius dot matrix structure slice data based on line segment set intersection approximation, in order to illustrate the effectiveness of the method of the present application, the above technical solutions of the present application will be described in detail below through a specific embodiment, the specific implementation steps are as follows:

[0050] Step S1, setting a node set and a rod set of a geometric model; a lattice structure is formed based on the node set and the rod set; the rod set includes a plurality of rods; each rod represents a connection relationship between nodes;

[0051] Analyzing geometric information of the geometric model three-dimensional lattice structure to obtain a plurality of geometric information; each geometric information includes three-dimensional coordinates of each node and start point coordinates and end point coordinates of each rod;

[0052] Uniformly slicing the geometric model three-dimensional lattice structure along the z-axis direction to obtain a plurality of slice planes;

[0053] Step S2, let e = 1, when e = 1, it represents the first rod; when n = 1, it represents the nth slice plane;

[0054] Converting the e-th rod into a corresponding truncated cone; the truncated cone is a line segment set; the upper and lower radii of the truncated cone are equal or not equal;

[0055] Based on the start point coordinates and the end point coordinates of the e-th rod, the start point coordinates and the end point coordinates of each line segment in the line segment set are obtained;

[0056] Step S3, obtaining the layer height of the nth slice plane;

[0057] Based on the start point coordinates and the end point coordinates of each line segment in the line segment set corresponding to the e-th rod and the layer height of the nth slice plane, a parameter equation of the intersection of each line segment and the nth slice plane is established; the parameter equation of the intersection of each line segment and the slice plane is solved to obtain the intersection points of each line segment in the e-th rod and the nth slice plane;

[0058] It can be understood that the layer height of the nth slice plane is the height difference between the slice planes; preferably, the expression of the parameter equation of each line segment and the nth slice plane is:

[0059] z1+t(z2-z1)=z k ,0≤t≤1

[0060] Wherein, t is the intersection parameter of the line segment and the plane, if t takes [0, 1], it represents that the line segment intersects with the plane, z k is the position of the slice plane, z1 is the start point coordinate of the z-axis coordinate of the line segment, and z2 is the end point coordinate of the z-axis coordinate of the line segment.

[0061] Step S4, fitting the intersection points of each line segment and the nth slice plane in step S3 to generate the contour projection of the e-th rod on the nth slice plane, converting the contour projection of the e-th rod on the nth slice plane into a two-dimensional pixel map according to the manufacturing precision and the discretization requirement to obtain the two-dimensional pixel map of the e-th rod on the nth slice plane.

[0062] Preferably, in step S4, the projection of the outline of the e-th rod on the n-th slice plane is the minimum circumscribed rectangle of the geometric outline, which is expressed as:

[0063] AABB e，n ={(x min，e，n ,y min，e，n ), (x max，e，n ,y max，e，n )}

[0064] Among them, AABB e，n is the minimum circumscribed rectangle of the geometric outline of the projection of the outline of the e-th member on the n-th slice plane, that is, the axis-aligned bounding box; mine，n is the minimum value of the projection of the contour of the e-th member on the n-th slice plane in the x-axis direction, y mine，n is the minimum value of the projection of the contour of the e-th member on the n-th slice plane in the y-axis direction; x max，e，n is the maximum value of the contour projection of the e-th member on the n-th slice plane in the x-axis direction; y max，e，n is the maximum value of the contour projection of the e-th member on the n-th slice plane in the y-axis direction.

[0065] Preferably, the expression of the two-dimensional pixel image of the e-th rod on the n-th slice plane in step S4 is:

[0066]

[0067]

[0068] Among them, u e，n v is the x-axis coordinate of the two-dimensional pixel image of the e-th rod on the n-th slice plane; e，n is the y-axis coordinate of the two-dimensional pixel image of the e-th rod on the n-th slice plane; e，n is the x-axis coordinate of the mapped point of the e-th member in the original contour diagram on the n-th slice plane; e，n is the y-axis coordinate of the mapped point of the e-th member in the original contour image on the n-th slice plane;

[0069] W is the width of the pixel image, and H is the height of the pixel image.

[0070] Step S5: Determine whether n is greater than or equal to N, where N represents the total number of slice planes. If so, obtain a two-dimensional pixel map of the line segment set corresponding to the e-th member on each slice plane and proceed to the next step; if not, set n = n + 1 and return to step S3;

[0071] Step S6, judging whether e is greater than or equal to E, if yes, obtaining the two-dimensional pixel map of the line segment set corresponding to each rod in the lattice structure of the geometric model in each layer slice plane, i.e. the two-dimensional pixel map in each layer slice plane; if no, setting e = e + 1 and returning to step S3;

[0072] Step S7, combining the two-dimensional pixel maps in each layer slice plane into complete slice data by a Boolean addition method to obtain the slice data of each layer slice plane;

[0073] Preferably, the expression of the slice data of each layer slice plane in step S7 is as follows:

[0074]

[0075] wherein, P final,n (x, y) is the x-axis coordinate and y-axis coordinate of the n-th layer slice plane; P n (x, y) is the x-axis coordinate and y-axis coordinate of the n-th layer slice plane.

[0076] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation, characterized in that: include: Step S1, setting the node set and member set of the geometric model; The lattice structure of the geometric model is constructed based on the node set and the rod set; Obtaining the three-dimensional coordinates of each node in the geometric model lattice structure and the starting point coordinates and end point coordinates of each rod; slicing the geometric model lattice structure to obtain multi-layer slicing planes; Step S2: let e=1, when e=1, it represents the first rod; when n=1, it represents the n-th slice plane; transform the e-th rod into a corresponding frustum; the frustum is a set of line segments; Obtain the starting point coordinates and ending point coordinates of each line segment in the line segment set based on the starting point coordinates and ending point coordinates of the e-th rod; Step S3, obtaining the layer height of the nth slice plane; Obtain the intersection points of each line segment in the e-th member and the n-th slice plane based on the layer height of the n-th slice plane; Step S4: Fitting the intersection points of each line segment in step S3 with the n-th slice plane and performing contour projection conversion to obtain a two-dimensional pixel image of the e-th rod on the n-th slice plane; Step S5: Determine whether n is greater than or equal to N, where N represents the total number of slice planes. If so, obtain a two-dimensional pixel map of the line segment set corresponding to the e-th member on each slice plane and proceed to the next step; if not, set n = n + 1 and return to step S3; Step S6: Determine whether e is greater than or equal to E. If so, obtain a two-dimensional pixel map of each slice plane corresponding to the line segment set of each rod in the lattice structure of the geometric model, that is, a two-dimensional pixel map of each slice plane; if not, set e=e+1 and return to step S3; Step S7: Combining the two-dimensional pixel images in each slice plane into complete slice data by using the Boolean sum method to obtain the slice data of each slice plane.

2. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 1, characterized in that: The specific steps of obtaining the three-dimensional coordinates of each node in the lattice structure of the geometric model and the starting point coordinates and the end point coordinates of each rod in step S1 include: The geometric information of the lattice structure of the geometric model is analyzed to obtain a plurality of geometric information; based on the geometric information, the three-dimensional coordinates of each node and the starting point coordinates and the end point coordinates of each rod are obtained.

3. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 1, characterized in that: The specific steps of obtaining the intersection points of each line segment in the e-th rod and the n-th slice plane in step S3 include: The parametric equations of the intersection of each line segment and the nth slice plane are established by collecting the starting and ending coordinates of each line segment in the line segment set corresponding to the eth member and the floor height of the nth slice plane; The intersection parameter equations of the line segments and the slice plane are solved to obtain the intersection points of the line segments in the e-th member and the n-th slice plane.

4. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 1, characterized in that: The specific steps of obtaining the two-dimensional pixel image of the e-th rod on the n-th slice plane in step S4 include: Fit the intersection points of each line segment in step S3 with the slice plane of the nth layer, Generate the contour projection of the e-th rod on the n-th slice plane, convert the contour projection of the e-th rod on the n-th slice plane into a two-dimensional pixel image according to the manufacturing accuracy and discretization requirements, and obtain the two-dimensional pixel image of the e-th rod on the n-th slice plane.

5. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 1, characterized in that: The layer height of the nth slice plane in step S3 is the height difference between the slice planes of each layer.

6. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 3, characterized in that: The parametric equations of each line segment and the nth slice plane are expressed as: z1+t(z2-z1)=z k ,0≤t≤1 Among them, t is the intersection parameter of the line segment and the plane, z k is the position of the slice plane, z1 is the starting coordinate of the z-axis coordinate of the line segment, and z2 is the ending coordinate of the z-axis coordinate of the line segment.

7. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 1, characterized in that: In step S4, the projection of the outline of the e-th member on the n-th slice plane is the minimum circumscribed rectangle of the geometric outline, which is expressed as: AABB e,n ={(x min,e,n ,y min,e,n ),(x max,e,n ,y max,e,n )} Among them, AABB e,n is the minimum circumscribed rectangle of the geometric outline of the projection of the outline of the e-th member on the n-th slice plane, that is, the axis-aligned bounding box; min,e,n is the minimum value of the projection of the contour of the e-th member on the n-th slice plane in the x-axis direction, y min,e,n is the minimum value of the projection of the contour of the e-th member on the n-th slice plane in the y-axis direction; x max,e,n is the maximum value of the contour projection of the e-th member on the n-th slice plane in the x-axis direction; y max,e,n is the maximum value of the contour projection of the e-th member on the n-th slice plane in the y-axis direction.

8. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 7, characterized in that: The expression of the two-dimensional pixel image of the e-th rod on the n-th slice plane in step S4 is: Among them, u e,n is the x-axis coordinate of the two-dimensional pixel image of the e-th rod on the n-th slice plane; v e,n is the y-axis coordinate of the two-dimensional pixel image of the e-th rod on the n-th slice plane; e,n is the x-axis coordinate of the mapped point of the e-th member in the original contour diagram on the n-th slice plane; e,n is the y-axis coordinate of the mapped point of the e-th member in the original contour image on the n-th slice plane; W is the width of the pixel image, and H is the height of the pixel image.

9. The method for obtaining variable radius lattice structure slice data based on line segment set intersection approximation according to claim 1, characterized in that: The expression of the slice data of each slice plane in step S7 is: Among them, P final,n (x, y) is the x-axis coordinate and y-axis coordinate of the n-th slice plane; P n (x,y) is the x-axis coordinate and y-axis coordinate of the n-th slice plane.

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