CN106408662B

CN106408662B - A kind of STL model modelling approach based on Grid model

Info

Publication number: CN106408662B
Application number: CN201610824044.5A
Authority: CN
Inventors: 陈新保
Original assignee: Hunan University of Science and Technology
Current assignee: Hunan University of Science and Technology
Priority date: 2016-09-14
Filing date: 2016-09-14
Publication date: 2019-03-12
Anticipated expiration: 2036-09-14
Also published as: CN106408662A

Abstract

The invention discloses a kind of STL model modelling approach based on Grid model, passes through conversion Grid model and establish the comprehensive wall in six faces, export STL model after generating the triangulation network, connection 3D printer can print the STL model.The structure feature that the method that the present invention uses passes through analysis STL model and Grid model, it is incision with ESRI Grid model, by computer programming, realize conversion and generation of the Grid model to STL model, this method solves the problems, such as that current Grid model can not directly generate 3D printing model, the three-dimensional real object for effectively extending two dimensional terrain figure is presented, significant increase its application value, especially military field and geographical mapping analysis field.

Description

A kind of STL model modelling approach based on Grid model

Technical field

The present invention relates to a kind of STL model modelling approach based on Grid model, specially based on the STL mould of Grid model Type modeling method belongs to geographical information technology conversion art.

Background technique

Digital elevation model (Digital Elevation Model), vehicle economy M are by limited landform altitude number It is factually existing that landform Surface Digitizing simulation (i.e. the digital expression of topographical surface form), it is with one group of orderly array of values Form indicates a kind of actual ground model of ground elevation, is digital terrain model (Digital Terrain Model, abbreviation DTM a branch).Grid model, that is, Rule acquisition is the important memory module and current number for characterizing topographical surface One of word elevation model mainstream form of expression.It is regular grid unit, each grid list that the model, which is by regional space cutting, The corresponding elevation numerical value of member, is widely used to the fields such as city planning and administration, military tactical strategic commanding.ESRI Grid format is that ESRI company in the U.S. characterizes one of most commonly seen format of Grid Rule acquisition at present.

The equal grid of the well-regulated ranks spacing of Grid model tool (as shown in Figure 1a), ranks number be respectively ncols and nrows；The corresponding height value (h) of each grid unit (cellsize, cell size).Wherein, ESRI Grid tray Formula is the raster data memory module of ArcGIS software official, and structure includes header format and data format, the sky of grid Between position determined by the position of lower left corner pixel.Header format is made of keyword and the information of pairing, data format portion Divide behind file header, each pixel value is by space-separated.The data text of ESRI Grid model is presented below as face data example.

Data instance:

STL (Stereo lithography) model, that is, three-dimensional entity model, physical model is to determine three in triangle On the basis of a data point data, by one group by spatial position, the line in Different Plane is connected with each other, physical model It is the basis for establishing threedimensional model.Three-dimensional entity model can handle to obtain 3D printing model by trigonometric ratio.The file of the model Format is the interface protocol that 3D SYSTEM company, the U.S. formulated in 1988, has evolved into current industrial circle mainstream standard.Due to STL structure mould is simple, readily understood, indicates 3D printing model with the triangulation network, can be widely applied to Quick-forming, virtual reality, numerical control The 3D printing technique fields such as processing, finite element analysis.

STL model (Fig. 1 b) is a kind of data with many spaces small tri patch (triangulation network) Approximation of 3 D solid object surface Model, the data of STL model pass through 3 components for providing composition triangulation method vector (for determining the positive negative side of tri patch To) and 3 apex coordinates of triangle realize.STL model shows as STL document format data, a complete stl file Describe the normal vector data and vertex coordinates data information of all triangle surfaces of composition physical model.Each triangle top Putting in order for point follows right-hand rule.Stl file is divided into ASCII clear format and two kinds of binary format at present.

The storage ASCII fromat of the STL model is as follows:

Wherein: being 1. user-defined file head；2. being three component values of tri patch normal vector；4. being tri patch three The coordinate on vertex；8. to complete a tri patch definition.

Currently, Grid model cannot be supported by the 3D printing equipment manufacturer of mainstream, cannot direct 3D printing.It is existing Paper base 3D printing method disclosed in disclosed Chinese patent CN105479742A based on NSDTF-DEM data, wherein disclosing Conversion regime be to realize that conversion generates model based on specific third party software, and be only able to carry out paper base 3D printing, no With versatility.Therefore, the universal transform method that 2D model data can be converted to 3D model data by developing one kind is this field Urgent problem to be solved when conversion.

Summary of the invention

In view of the above-mentioned problems existing in the prior art, the object of the present invention is to provide one kind.

For achieving the above object, The technical solution adopted by the invention is as follows:

STL model modelling approach based on Grid model passes through conversion Grid model and establishes the comprehensive wall in six faces, generates three STL model is exported after the net of angle, connection 3D printer can print the STL model.

Preferably, the STL model modelling approach based on Grid model includes the following steps:

A. Grid model is read to be read from left to right, from the bottom up using lower-left angular coordinate as origin coordinates to upper right corner height Cheng Dian, while height value and coordinates computed point value are read with grid unit interval (cellsize), and corresponding array is written；

B. model dimension is converted, by the geographical coordinate of Grid model and height value bi-directional scaling, printer model coordinate；

C. thick embryo STL model modeling carries out three-dimensional lifting to Grid model, establishes Nan Qiang, north wall, Dong Qiang and western wall four Side wall constitutes six comprehensive walls with bottom and ground surface；

D. according to the right-hand rule, the side wall triangulation network is constructed, adjacent two vertex in side wall edge and its corresponding bottom apex are two-by-two Connection, forms two triangles；

E. the bottom triangulation network and the ground surface triangulation network are constructed according to right-hand rule；

F. using the Grid model lower left corner as starting point, from left to right, triangular facet is sequentially generated from the bottom up, establish STL model.

Preferably, when reading Grid model, reading information includes geographical coordinate point value and height value, the Grid model lower left corner Coordinate is origin (xllcorner, yllcorner), and ranks number is respectively nrows and ncols, and reading process is successively from original Point coordinate the first row starts from left to right, carries out from the bottom up, until most upper right corner elevational point；At interval of unit (cellsize) An elevational point is obtained, which can be obtained by calculation (xllcorner+n*cellsize, yllcorner+n* cellsize)。

It is respectively written into, the coordinate and height value of all elevational points for storing X-coordinate number according to the read-write sequence Group (xList [nrows*ncols]), Y-coordinate array (yList [nrows*ncols]) and height value array (hList [nrows*ncols])。

Preferably, model dimension switch process specifically: the scaling factor for calculating geographical coordinate point value is calculated and beaten X-axis and Y axis coordinate are printed, setting benchmark is high, calculates the scaling factor of elevation, printing Z axis coordinate is calculated,

Known Grid model geographical coordinate regional scope (minLon, minLat, maxLon, maxLat), elevation array The embryo of hList [nrows*ncols], STL 3D printing model have specification (Length*width*height), solve two model Between size conversion process:

1., calculate the scaling factor on X and Y-axis between two models:

ScaleX=(maxLon-minLon)/Length；

ScaleY=(maxLat-minLat)/Width；

2., setting benchmark it is high (BaseHeight), the pedestal as printer model:

BaseHeigth=heigth/4；// take empirical value height/4

3., calculate the scaling factor on Z axis between two models:

Graph=hList.Max ()-hList.Min ()；// elevation maxima and minima is poor

ScaleZ=graph/ (height-BaseHeight)；

4., calculate printer model coordinate:

X=(lon-minLon)/scaleX；//X--- printer model X axis coordinate

Y=(lat-minLat)/scaleY；//Y--- printer model Y axis coordinate

Z=BaseHeight+ (h-hList.Min ())/scaleZ.

It is furthermore preferred that when three-dimensional lifting Grid model, with a height of lifting scale of benchmark.

It is furthermore preferred that southern wall triangle vertex of surface is counterclockwise to arrange, north wall triangular facet top when the building side wall triangulation network Point is arranges clockwise, in Fig. 4 a, southern tetra- adjacent vertex of wall a, b, z and w (i.e. elevational point), wherein a and b be ground surface most Two vertex of south edge, z and w are corresponding bottom apex, a and b connecting line L₁, a and z connecting line L₂, b and w connecting line L₃, b and W connecting line L₄.STL model is generated, increases the connecting line L of b and z newly₀, then form two triangle S₁(a, b, z) and S₂(b、z、 w)。

With S₁For (a, b, z), the normal vector of the triangle is solved, it then follows calculate step below:

Var ab:Object=new Object ()；

Ab.x=a.x-b.x；

Ab.y=a.y-b.y；

Ab.h=a.h-b.h；

Var bc:Object=new Object ()；

Bz.x=b.x-z.x；

Bz.y=b.y-z.y；

Bz.h=b.h-z.h；

Then normal is calculated, i.e. another vector.Seek the normal vector (norm) of the triangle:

Var norm:Object=new Object ()；

Norm.x=(ab.y*bz.h)-(ab.h*bz.y)；

Norm.y=- ((ab.x*bz.h)-(ab.h*bz.x))；

Norm.z=(ab.x*bz.y)-(ab.y*bz.x)；

North wall (Fig. 4 b), Dong Qiang (Fig. 4 a) He Xiqiang (Fig. 4 b) are similar.

It is furthermore preferred that when the bottom triangulation network constructs, with the lower left corner (0,0,0) point for starting point, on diagonal two adjacent edges Each point is terminal, is sequentially connected starting point and each point in the direction of the clock, forms several triangles, with first company on adjacent edge Contact and the last one tie point are respectively starting point, and each point on connection (0,0,0) point adjacent side forms several reversed triangles, It is non-overlapping between all triangles.

It is furthermore preferred that when the bottom triangulation network constructs, using any point of boundary point non-in region as starting point, by side counterclockwise To fillet each point, several nonoverlapping triangles are formed.

It is furthermore preferred that being endpoint formation triangle, two o'clock when connection using four adjacent elevational points when the building earth's surface triangulation network Between depth displacement be more than or equal to another two o'clock depth displacement.

By the triangulation network of Grid model conversion and generation STL model: with the Grid model lower left corner (origin) for starting point, from Left-to-right (horizontal axis) sequentially generates triangular facet from top to bottom (longitudinal axis)；At the same time, according to the right-hand rule of STL model, sternly Lattice record three vertex of the triangular facet and acquire its normal vector according to sequence；By programming, a read/write function is created, is pressed According to the storage rule (ASCII fromat) of characterization STL model, exports and save into * .stl file format.

Compared with prior art, the method that the present invention uses passes through the structure feature of analysis STL model and Grid model, with ESRI Grid model is incision, by computer programming, realizes conversion and generation of the Grid model to STL model.This method has Effect solves the problems, such as that current Grid model can not directly generate 3D printing model, and the solid for effectively extending two dimensional terrain figure is real Object is presented, significant increase its application value, especially military field and geographical mapping analysis field.

In short, method 3D printing model generated provided by the invention is exquisite, effect is preferable, it can with being directly printed as 3D Shape model.The conversion and generation method can be converted for other digital elevation models (such as HGT model, TIN model) and generate STL Printer model provides vantageous methods and uses for reference.

Detailed description of the invention

Fig. 1 is the flow chart of production method for transferring provided by the invention.

Fig. 2 is the Grid model elevational point reading process schematic diagram of production method for transferring provided by the invention.

Fig. 3 is that the thick embryo grade STL model of production method for transferring provided by the invention generates schematic diagram.

Fig. 4 is that the metope triangulation network of production method for transferring provided by the invention generates schematic diagram.

Fig. 5 is that the bottom triangulation network of production method for transferring provided by the invention generates schematic diagram.

Fig. 6 is that the ground surface triangulation network of production method for transferring provided by the invention generates schematic diagram.

Specific embodiment

The present invention is made further to illustrate in detail, completely below with reference to embodiment and comparative example.

Embodiment 1

Fig. 1 is the STL model modelling approach flow chart of the invention based on Grid model, as shown, this method includes Following steps:

(1) read and write step: data file of the read-write step for Grid model is read.The following are ESRI Grid data to deposit The embodiment that file is the method for the present invention is stored up, Fig. 2 visualizes presented Grid model for the case.It is advised according to being read in figure Then, the coordinate (x, y) and height value (h) of each elevational point are read and is calculated as read direction using arrow instruction direction, and divide It Xie Ru not xList [25], yList [25] and hList [25] array.

In the present embodiment, it may be programmed and read following basis parameter:

Ncols=5, nrows=5, cellsize=2, xllcorner=2.0, yllcorner=5, hList etc..Into And can obtain the Grid model geographical coordinate regional scope: (2.02.012.0,12.0), altitude data hList [25] are as follows:

Elevation array: hList [25]=10.0,10.0,10.0,10.0,10.0,

10.0,20.0,20.0,20.0,10.0

10.0,20.0,40.0,20.0,10.0,

10.0,20.0,20.0,20.0,10.0,

10.0,10.0,10.0,10.0,10.0 }；Wherein hList.Max ()=40；HList.Min ()=10；

It is calculated by formula (xllcorner+n*cellsizeyllcorner+n*cellsize), wherein n=0~4, point It does not obtain:

X array: xList [25]={ 2.0,4.0,6.0,8.0,10.0//Grid model X axis coordinates

2.0,4.0,6.0,8.0,10.0

2.0,4.0,6.0,8.0,10.0 }；

Y array: yList [25]={ 2.0,2.0,2.0,2.0,2.0//Grid model Y axis coordinates

4.0,4.0,4.0,4.0,4.0

6.0,6.0,6.0,6.0,6.0,

8.0,8.0,8.0,8.0,8.0,

10.0,10.0,10.0,10.0,10.0 }.

(2) modeling procedure: conversion and generation of the step for Grid model to STL model.The specific sub-step of the step Are as follows:

Step 1: model dimension is converted.In the present embodiment, the specification [5*5*5] of 3D printing embryo mold, by Grid model Elevational point coordinate and its height value, according to following steps and formula, conversion to new moulded dimension forms new coordinate points Group.

1., calculate the scaling factor on X and Y-axis between two models:

ScaleX=(12-2)/5=2；

ScaleY=(12-2)/5=2；

2., setting benchmark it is high (BaseHeight), the pedestal as printer model:

BaseHeigth=5/4=1.25；// take empirical value height/4

3., calculate the scaling factor on Z axis between two models:

Graph=40-10=30；// elevation maxima and minima is poor

ScaleZ=30/ (5-1.25)=8；

4., calculate printer model coordinate:

X=(lon-2)/2；//X--- printer model X axis coordinate

Y=(lat-2)/2；//Y--- printer model Y axis coordinate

Z=1.25+ (h-10)/8；

H3List [25]={ 1.25,1.25,1.25,1.25,1.25//printer model Z axis coordinate

1.25,2.50,2.50,2.50,1.25,

1.25,2.50,3.75,2.50,1.25,

1.25,2.50,2.50,2.50,1.25,

1.25,1.25,1.25,1.25,1.25 }；

X3List [25]={ 0.0,1.0,2.0,3.0,4.0//printer model X axis coordinate

0.0,1.0,2.0,3.0,4.0

0.0,1.0,2.0,3.0,4.0 }；

Y3List [25]={ 0.0,0.0,0.0,0.0,0.0//printer model Y axis coordinate

1.0,1.0,1.0,1.0,1.0

2.0,2.0,2.0,2.0,2.0,

3.0,3.0,3.0,3.0,3.0,

4.0,4.0,4.0,4.0,4.0 }.

Step 2: thick embryo grade STL model generates.As shown in figure 3, with benchmark high (BaseHeigth=1.25) for scale, Three-dimensional lifting is carried out to Grid terrain model, as the pedestal of printer model, and then shape coarse-blank grade) STL model, i.e., it does not give birth to At the STL model of triangular facet.The model generates six comprehensive walls, i.e. Nan Qiang, north wall, Dong Qiang, Xi Qiang, bottom, ground surface etc. Six comprehensive walls (face).

Step 3: the metope triangulation network generates.As shown in fig. 4 a, it then follows right-hand rule constructs three tops of southern wall triangular facet Point puts in order as counterclockwise.In fig.4, southern tetra- adjacent vertex of wall a, b, z and w (i.e. elevational point), wherein a and b is ground Two vertex of surface edge southernmost, z and w are corresponding bottom apex, a and b connecting line L₁, a and z connecting line L₂B and w connecting line L₃, b and w connecting line L₄.STL model is generated, increases the connecting line L of b and z newly₀, then form two triangle S₁(a, b, z) and S₂ (b、z、w)。

With S₁For (a, b, z), wherein a (2,0,1.25), b (1,0,1.25) and z (1,0,0), solve the triangle Normal vector, it then follows following steps:

Var ab:Object=new Object ()；

Ab.x=2-1=1；

Ab.y=0-0=0；

Ab.h=1.25-1.25=0；

Var bc:Object=new Object ()；

Bz.x=1-1=0；

Bz.y=0-0=0；

Bz.h=1.25-0=1.25；

Calculate the normal vector of the triangle.Seek the normal vector (norm) of the triangle: (0,0,0)

Varnorm:Object=newObject ()；

Norm.x=(0*1.25)-(0*0)=0；

Norm.y=- ((1*0)-(0*0))=0；

Norm.z=(1*0)-(0*1)=0；

North wall (Fig. 4 b), Dong Qiang (Fig. 4 a) He Xiqiang (Fig. 4 b) are similar.

Step 4: the bottom triangulation network generates.The present embodiment selection " bottom is not necessarily to newly-increased point " scheme.In attached drawing 5 (b), The lower left corner is bottom origin and starting point, and according to clockwise, emitting shape connects opposite slightly to the right or left (top) point, forms " penetrating formula " triangle Net forms six triangles such as the 1st, 2,3,4,5,6 in attached drawing (b), then suitable for starting point with tiltedly upper first, angle (top) point Clockwise " penetrating shape formula " connects (top) point at its right opposite slightly to the right or left, forms four triangles such as the 7th, 8,9,10 in attached drawing (b). Similarly, with first, angle (top) point obliquely downward for starting point, " penetrating formula " connects (top) point at its left opposite slightly to the right or left clockwise, forms figure (b) four triangles such as the 11st, 12,13,14 in.

Step 5: the ground surface triangulation network generates.In figure 6, four adjacent vertexs a, b, c and d, if a point and c point height Difference is more than or equal to d point and b point height is poor, then is the line of a and c, and then forms two triangles (Fig. 6 a) of △ adc and △ cba； It is the line of b and d if a point is less than d point with c point height difference and b point height is poor, and then forms △ dcb and △ adb two three Angular (Fig. 6 b).

(3) it exports step: Grid model conversion and the triangulation network for generating STL model being exported with ASCII fromat, and exported And it saves into * .stl file format.Such as following figure S₁(abz) segment.It ultimately generates effect and sees Fig. 1 b.

Embodiment 2

The present embodiment and the difference of embodiment 1 are only that, in the present embodiment step 4: the production of the bottom triangulation network and implementation Example 1 is different.

Newly-increased point scheme is selected in the present embodiment, as shown in attached drawing 5 (a), non-boundary selects any point in region For vertex, the lower left corner (0,0,0) point is starting point, connects vertex and starting point, and traverse whole region in the counterclockwise direction, Mei Gefang If doing to setting, whole region is divided into several triangles without coincidence, wherein the point that each side is connect with vertex can be It is uniformly arranged, is also possible to non-uniform.

Be it is necessary to described herein finally: above embodiments are served only for making technical solution of the present invention further detailed Ground explanation, should not be understood as limiting the scope of the invention, those skilled in the art's above content according to the present invention The some nonessential modifications and adaptations made all belong to the scope of protection of the present invention.

Claims

1. a kind of STL model modelling approach based on Grid model, it is characterised in that: by conversion Grid model and establish six faces Comprehensive wall exports STL model after generating the triangulation network, and the modeling method includes the following steps:

A. Grid model is read to be read from left to right, from the bottom up using lower-left angular coordinate as origin coordinates to upper right corner elevation Point, while height value and coordinates computed point value are read with grid unit interval, and corresponding array is written；

C. thick embryo STL model modeling carries out three-dimensional lifting to Grid model, establishes Nan Qiang, four side of north wall, Dong Qiang and western wall Wall constitutes the comprehensive wall in six faces with bottom and ground surface；

D. according to the right-hand rule, the side wall triangulation network is constructed, adjacent two vertex in side wall edge and its corresponding bottom apex connect two-by-two, Form two triangles；

F. using the Grid model lower left corner as starting point, from left to right, triangular facet is sequentially generated from the bottom up, establish STL model；Its In, when the bottom triangulation network constructs, with the lower left corner (0,0,0) point for starting point, each point is terminal on diagonal two adjacent edges, by suitable Clockwise is sequentially connected starting point and each point, forms several triangles, is handed in the direction of the clock with flash trimming on the adjacent edge The last one point on first point and another adjacent edge outside point outside flash trimming intersection point is respectively starting point, connect (0, 0,0) each point on adjacent side is put, forms several reversed triangles, it is non-overlapping between all triangles；Or with boundary point non-in region Any point be starting point, fillet each point counterclockwise forms several nonoverlapping triangles.

2. the STL model modelling approach according to claim 1 based on Grid model, which is characterized in that model dimension turns Change step specifically: the scaling factor for calculating geographical coordinate point value calculates printing X-axis and Y axis coordinate, and benchmark is arranged Height calculates the scaling factor of elevation, calculates printing Z axis coordinate.

3. the STL model modelling approach according to claim 1 based on Grid model, it is characterised in that: three-dimensional lifting When Grid model, with a height of lifting scale of benchmark.

4. the STL model modelling approach according to claim 1 based on Grid model, it is characterised in that: building side wall three When angle is netted, southern wall triangle vertex of surface is counterclockwise to arrange, and north wall triangle vertex of surface is to arrange clockwise.

5. the STL model modelling approach according to claim 1 based on Grid model, it is characterised in that: building earth's surface three When angle is netted, triangle is formed by endpoint of four adjacent elevational points, the point-to-point transmission depth displacement for forming diagonal line connection is more than or equal to The depth displacement of another two o'clock.

6. the STL model modelling approach based on Grid model stated according to claim 2, it is characterised in that: Grid model is geographical Coordinates regional range (minLon, minLat, maxLon, maxLat), calculation formula of the scaling factor on X and Y-axis are as follows:

ScaleX=(maxLon-minLon)/Length；

ScaleY=(maxLat-minLat)/Width；

Wherein the embryo tool specification of STL 3D printing model is Length*Width*height.

7. the STL model modelling approach based on Grid model stated according to claim 2, it is characterised in that: Grid model is geographical Elevation array hList [nrows*ncols], the high BaseHeight of benchmark, calculation formula of the scaling factor on Z axis are as follows:

Graph=hList.Max ()-hList.Min ()；

ScaleZ=graph/ (height-BaseHeight)；