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StL Data File Viewer

, 5 Mar 2003 GPL3
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A simple StereoLithography data file viewer.

Sample Image - StLViewer.jpg

Introduction

StereoLithography(StL) is something that is widely used in CAD/CAM, RapidPrototyping etc. The concept is that any surface or solid is exported to StL format by data exchange packages after they are modeled in commercial CAD packages. This data consists of triangulated facets that approximate the surface of the solid. No topological or geometric information is exported. The surface is subdivided into small triangles. The approximation uses chordal deflection for curved surfaces to smoothen the surface. More the smoothening required, more number of smaller triangles are generated by subdivision resulting in larger size of data file. Now, along with triangles, their facet normals are also generated. The data is written both in ASCII and binary formats. The data in ASCII is written like this:

facet normal  0.000000e+000 -1.000000e+000  0.000000e+000
   outer loop
     vertex -1.499999e+002 -1.000000e+002  0.000000e+000
     vertex -1.500000e+002 -1.000000e+002  0.000000e+000
     vertex -1.500000e+002 -1.000000e+002 -5.000000e+001
   endloop
 endfacet

The facet normal tells the three components of the facet normal followed by three vertices of one triangle, enclosed by the statements.

facet normal  0.000000e+000 -1.000000e+000  0.000000e+000

and

endfacet

Thus all the triangles are written one after the other. This data can be then used as input for generating Rapid Prototype models as well as for NC toolpath generation. The Normal data helps to compute tool offsets etc.

Here, for displaying the data in the OpenGL viewer, I have written the code for reading the data and displaying each triangle using glBegin(GL_TRIANGLES) and the normals for lighting. The viewer and geometry coding is same as my earlier project CadSurf. You can read as many StL (ASCII only) files into the viewer zoom, pan, rotate the views, select the objects, change attributes like color and material. The viewer provides object oriented context menus. I.e., when you click the right mouse button in the view with no active selection, you get a context menu for setting the viewer attributes, whereas with StL object selected, you get menu for the object attributes. Some sample StL data is also provided in the Data folder of the project.

Please let me know your comments. Thank you.

License

This article, along with any associated source code and files, is licensed under The GNU General Public License (GPLv3)

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About the Author

Sharjith
Engineer Tata Technologies Ltd
India India
Sharjith is a Mechanical Engineer with strong passion for Automobiles, Aircrafts and Software development.

Comments and Discussions

 
AnswerRe: Unable to view the viewer after running the application PinmemberSharjith24-May-12 0:37 
GeneralRe: Unable to view the viewer after running the application PinmemberMember 105096748-Jan-14 6:22 
GeneralMy vote of 5 PinmemberVolynsky Alex23-May-12 3:42 
QuestionSlicing Pinmemberederson.nivel124-Apr-12 9:34 
QuestionSelection window on window 7 machine got distorted. Pinmembersingh96323-Apr-12 5:00 
Questionflash screen appear while resizing window Pinmembersingh96323-Apr-12 4:54 
QuestionRun-Time Check Failure #2 - Stack around the variable 'str' was corrupted. Pinmemberwaterharbin1-Mar-12 2:33 
AnswerRe: Run-Time Check Failure #2 - Stack around the variable 'str' was corrupted. PinmemberSharjith1-Mar-12 11:59 
GeneralSTL Viewer Pinmembercjellwood13-Feb-11 4:02 
GeneralRe: STL Viewer PinmemberSharjith13-Feb-11 5:54 
GeneralError [modified] Pinmembersangar202023-Sep-10 18:21 
GeneralRe: Error PinmemberSharjith24-Sep-10 7:28 
GeneralTell the path Pinmembersangar202023-Sep-10 0:54 
GeneralRe: Tell the path PinmemberSharjith23-Sep-10 4:42 
GeneralFatel error Pinmembersangar202022-Sep-10 23:48 
Questionfollowing message display in .net 2008? Pinmembersangar202022-Sep-10 18:12 
AnswerRe: following message display in .net 2008? PinmemberSharjith22-Sep-10 18:38 
GeneralDuplicated points removal PinmemberM.Siyamalan3-May-10 18:56 
GeneralRe: Duplicated points removal PinmemberSharjith3-May-10 19:40 
QuestionHow to calculate angle between triangles Pinmembernsivabalan202031-Mar-10 20:50 
AnswerRe: How to calculate angle between triangles PinmemberSharjith1-Apr-10 7:17 
GeneralUnable to open other stl file PinmemberMember 460375414-Feb-10 20:12 
GeneralStereolithography file (STL) edit Pinmembernsivabalan202030-Nov-09 19:25 
GeneralWat knowledge should i must have to handle this task PinmemberDevelopmentNoob21-Apr-09 17:58 
GeneralIs there component out there that can recognize the demension of stl and iges files PinmemberMember 14020139-Apr-09 5:56 

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