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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


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

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



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.


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


About the Author

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

Comments and Discussions

AnswerRe: I am very interested in the topological relation of triangles PinmemberSharjith18-Dec-06 5:15 
GeneralNC & RP code Pinmemberharshalmsrsas20-Nov-06 0:14 
AnswerRe: NC & RP code PinmemberSharjith18-Dec-06 5:07 
GeneralI want to use OpenGL with STL From Robotic 6 axis Pinmemberaluntum15-Feb-06 10:25 
QuestionI can't load other stl file Pinmemberqinhongxian19-Dec-05 7:24 
GeneralSlow and Selection should disabled out of the stl object Pinmemberlua8-Jun-05 2:03 
GeneralRe: Slow and Selection should disabled out of the stl object Pinmemberhero3blade24-Sep-05 17:09 
GeneralCould not complie a code PinmemberTejas_qp1-Mar-05 9:00 
GeneralRe: Could not complie a code PinmemberSharjith3-Mar-05 22:22 
GeneralRe: Could not complie a code Pinmember1vs18-Apr-05 20:44 
QuestionHow to run 2 different(or same) OpenGL objects in one DialogBox? Pinmemberwerter15-Jun-04 22:53 
GeneralOT: Starting Point Pinsusslj993234-Aug-03 17:48 
GeneralRe: OT: Starting Point Pinmemberjcdemo17-Mar-05 21:50 
GeneralCan't not #include <GL/glut.h> PinmemberICE_WIZARD24-Jul-03 8:25 
Can't not #include <GL/glut.h>
My problem is didn't have Glut3-7, isn't it? Could you tell me where I can download it?
GeneralRe: Can't not #include &lt;GL/glut.h&gt; PinmemberJonathan de Halleux24-Jul-03 8:35 
GeneralSTL viewer does not display Pinmemberreddnedk23-Jun-03 7:18 
GeneralRe: STL viewer does not display PinmemberSharjith26-Jun-03 6:14 
GeneralRe: STL viewer does not display PinsussAnonymous2-Jul-03 20:09 
Generalview Pinmembermcalves@coc.ufrj.br8-May-03 21:05 
QuestionHow does GL_SELECT mode work in MFC? Pinmemberkillerdoll18-Mar-03 6:33 
AnswerRe: How does GL_SELECT mode work in MFC? PinmemberSharjith28-Mar-03 3:01 
General0xC0000005: Access Violation. PinsussSorry I donnot know why I cannot fill in right con7-Mar-03 14:33 
GeneralRe: 0xC0000005: Access Violation. PinmemberSharjith7-Mar-03 20:48 
GeneralRe: 0xC0000005: Access Violation. PinmemberMy name is Iain Scott. Does it matter that there a25-Jun-06 2:12 
NewsRe: 0xC0000005: Access Violation. PinmemberSharjith28-Jun-06 23:00 

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