A self-supporting shell extraction method for a three-dimensional model

Abstract

The application discloses a three-dimensional model self-supporting shell extraction method, which comprises the following steps: 1) reversing all triangles of a three-dimensional model A, then calculating a bounding box to enclose the three-dimensional model A, combining the bounding box and the three-dimensional model A to generate a model B; 2) generating a support for the model B, combining the support and the model B to generate a model C; 3) removing the bounding box generated in step 1 from the model C, then reversing the normal of the remaining triangle to obtain a model D; 4) uniformly and equally thickly extracting the shell of the model D to obtain an extracted shell model E; setting the triangle of the model E more than the model D as a model F; 5) combining the model F and the original model A to obtain a model G. When the model is three-dimensionally printed, the application does not need to add a support structure inside a newly generated shell, which brings convenience to the processing after the model is printed, and meanwhile, the model is extracted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of advanced manufacturing, and particularly relates to a three-dimensional model self-supporting shell extraction method. BACKGROUND

[0002] With the development of science and technology, industrial manufacturing capacity has become an important indicator for evaluating the comprehensive national power of each country. In the field of manufacturing or three-dimensional printing, three-dimensional model shell extraction is a common operation. The purpose of three-dimensional model shell extraction can be roughly divided into two aspects: one is to manufacture a hollow model or part (such as a bottle, which is hollow inside and can hold things), and the other is to save materials and processing time. For example, in common three-dimensional printing, through shell extraction, the model volume is greatly reduced, which greatly reduces the printing time and saves a lot of expensive printing materials, thereby saving costs. The common shell extraction refers to uniform and equal-thickness shell extraction, and the self-supporting shell extraction is a variable-thickness shell extraction. The purpose is that the three-dimensional model after shell extraction does not need to add a support structure to the shell generated by self-supporting shell extraction. In this way, the time for the operator to remove the support can be saved. Otherwise, if the operator performs uniform and equal-thickness shell extraction, the shell generated by the shell extraction needs to add a support structure. In order to remove the support structure of the internal shell, the operator needs to cut the printed model, remove the support structure, and then splice the cut model together. In this way, the quality of the model is compromised.

[0003] At home and abroad, many three-dimensional software have shell extraction functions. They perform shell extraction on traditional CAD format files or triangular mesh models. However, their shell extraction is uniform and equal-thickness, which is not self-supporting shell extraction. Some three-dimensional software have self-supporting shell extraction functions. However, their algorithms are slow, occupy high memory, or the effect is not very good.

[0004] In existing academic papers and the latest research progress, many scholars have proposed different self-supporting shell extraction algorithms, but their defects are still as follows: 1) the algorithm complexity is too high, especially for complex structure models, the calculation time is too long; 2) the algorithm effect is not good, and many small cavities are generated, which is not good in three-dimensional printing. SUMMARY

[0005] The present application relates to the field of advanced manufacturing, and particularly relates to a three-dimensional model self-supporting shell extraction method.

[0006] To achieve the above object, the present application provides the following technical scheme.

[0007] A three-dimensional model self-supporting shell extraction method comprises the following steps:

[0008] 1), reverse all triangles of three-dimensional model A, then calculate a bounding box and surround three-dimensional model A, combine the bounding box and three-dimensional model A, generate model B;

[0009] 2), according to the user set self-supporting angle, generate support, combine the support and model B, generate model C;

[0010] 3), remove the bounding box generated in step 1 from model C, then flip the remaining triangle normal to get model D;

[0011] 4), according to the user input shell thickness, perform uniform and equal thickness shell extraction to get the shell extracted model E; set the triangle of model E more than model D as model F;

[0012] 5), merge model F and original model A to get model G.

[0013] As a further scheme of the application: before step 1, the model self-supporting angle meeting the three-dimensional printing requirement needs to be set in advance.

[0014] As a further scheme of the application: before step 1, the shell thickness needs to be set in advance.

[0015] Compared with the prior art, the beneficial effects of the application are: the self-supporting shell extraction algorithm of the three-dimensional model can not add support structure inside the newly generated shell when the model is three-dimensionally printed, which brings convenience to the processing after the model is printed, and saves printing materials and costs. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a schematic diagram of model A in the application.

[0017] Figure 2 It is a cross-sectional schematic diagram of model A in the application.

[0018] Figure 3 It is a schematic diagram of model B in the application.

[0019] Figure 4 It is a cross-sectional schematic diagram of model B in the application.

[0020] Figure 5 It is a schematic diagram of model C in the application.

[0021] Figure 6 It is a cross-sectional schematic diagram of model C in the application.

[0022] Figure 7 It is a schematic diagram of model D in the application.

[0023] Figure 8 This is a cross-sectional schematic diagram of model D in this invention.

[0024] Figure 9 This is a schematic diagram of model E in this invention.

[0025] Figure 10 This is a cross-sectional schematic diagram of model E in this invention.

[0026] Figure 11 This is a schematic diagram of model F in this invention.

[0027] Figure 12 This is a schematic cross-sectional view of model F in this invention.

[0028] Figure 13 This is a schematic diagram of model G in this invention.

[0029] Figure 14 This is a cross-sectional schematic diagram of model G in this invention.

[0030] Figure 15 This is a schematic diagram of the model in an embodiment of the present invention.

[0031] Figure 16 This is a cross-sectional schematic diagram of the model in an embodiment of the present invention.

[0032] Figure 17 This is a schematic diagram of the self-supporting shelled model in an embodiment of the present invention.

[0033] Figure 18 This is a schematic cross-sectional view of the self-supporting shell of the model in the embodiment of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In this embodiment of the invention, a self-supporting shelling method for a 3D model requires the user to set a self-supporting angle of the model that meets the requirements of 3D printing, such as 45°, and also to set the shelling thickness. The method includes the following steps:

[0036] 1) such as Figure 1 , 2, the three-dimensional model A, such as a.stl format file, reverse all the triangles of the model A, that is, change the normal direction of the triangles of the model from the original outward direction to inward direction; then calculate a bounding box (cuboid) that can surround the three-dimensional model, combine the bounding box and the model to generate model B, such as Figure 3 、 4 ;

[0037] 2) According to the self-supporting angle angle set by the user, generate supports for the model B, and the generated supports only need to meet the self-supporting angle, without being vertically downward, combine the supports and the model B to generate model C, such as Figure 5 、 6 ;

[0038] 3) Remove the bounding box generated in step 1 from the model C, and then flip the normal direction of the remaining triangles to obtain model D, such as Figure 7 、 8 ;

[0039] 4) According to the shell thickness input by the user, perform uniform and equal-thickness shell extraction on the model D to obtain the shell-extracted model E, such as Figure 9 、 10 ; the part that is added by the uniform and equal-thickness shell extraction is model F, F = E-D, such as Figure 11 、 12 ;

[0040] 5) Merge the model F and the original model A to obtain model G, which is the final result we need, such as Figure 13 、 14 .

[0041] Example, for a frog model with length, width and height of 60mm, 43mm and 58mm respectively, such as Figure 15 、 16 , the shell thickness is 2mm, and the self-supporting angle is 45°, and the above steps are used to perform self-supporting shell extraction to obtain a model such as Figure 17 、 18 .

[0042] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0043] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made specifically within that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.

Claims

1. A method of self-supporting shell extraction of a three-dimensional model, characterized by: It comprises the following steps: 1) reverse all triangles of the three-dimensional model A, then calculate a bounding box and enclose the three-dimensional model A, combine the bounding box and the three-dimensional model A to generate model B; 2) generate support according to a self-supporting angle for model B, combine the support and model B to generate model C; 3) remove the bounding box generated in step 1 for model C, then flip the normal of the remaining triangles to obtain model D; 4) uniformly and equally-thickly hollow the model D to obtain the hollowed model E; set the triangles of model E more than model D as model F; 5) combine model F and the original model A to obtain model G, which is the three-dimensional model to be hollowed.

2. A method of self-supporting shell extraction of a three-dimensional model according to claim 1, characterized in that: Before the step 1, the model self-supporting angle meeting the three-dimensional printing requirement needs to be set in advance.

3. A method of self-supporting shell extraction of a three-dimensional model according to claim 1, characterized in that: Before the step 1, the hollowing thickness needs to be set in advance.

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