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Posted 5 Mar 2003
Licenced CPOL

StL Data File Viewer

, 5 Mar 2003
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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 Code Project Open License (CPOL)


About the Author

Product Manager Mahindra & Mahindra
India India
Sharjith is a Mechanical Engineer with strong passion for Automobiles, Aircrafts and Software development.

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Comments and Discussions

AnswerRe: how to convert CL data file to G codes/machine language Pin
Sharjith9-Feb-09 2:29
memberSharjith9-Feb-09 2:29 
GeneralRe: how to convert CL data file to G codes/machine language Pin
dixitava9-Feb-09 19:06
memberdixitava9-Feb-09 19:06 
GeneralRe: how to convert CL data file to G codes/machine language Pin
dixitava11-Feb-09 18:07
memberdixitava11-Feb-09 18:07 
GeneralRe: for which controller Pin
dixitava11-Feb-09 18:09
memberdixitava11-Feb-09 18:09 
QuestionHow can I contact you? Pin
jemmyell12-Dec-08 7:13
memberjemmyell12-Dec-08 7:13 
AnswerRe: How can I contact you? Pin
Sharjith15-Dec-08 4:47
memberSharjith15-Dec-08 4:47 
General[Message Deleted] Pin
avajja17-Oct-08 19:02
memberavajja17-Oct-08 19:02 
GeneralRe: How to View STL file in BINARY format Pin
Sharjith23-Oct-08 6:34
memberSharjith23-Oct-08 6:34 
First of all the StL format is only vertex and normal data and not curves or surface data. Then what are you planning to write into the iges file? What you can export as iges data is only Point and Triangular face and edge data but that won't smoothen your data. What is the objective in converting stl to iges. Conversion of Iges to Stl can be understood.

You may use the code freely in your project. Smile | :)
To read the binary format file of stl data you will have to wite a separate algo.

I do have the code I downloaded from the net once upon a time. If you want I will send it... the website doesn't exist now so I can send it to your personal mail.

RegardsSmile | :)
N. Sharjith

Questionthanks in advance Pin
garyzhg18-Jul-08 23:44
membergaryzhg18-Jul-08 23:44 
QuestionGenport I/O initialitazion failure Pin
Vinod_code25-Sep-07 0:03
memberVinod_code25-Sep-07 0:03 
Generaldimension of stl Pin
saisp22-Jul-07 21:42
membersaisp22-Jul-07 21:42 
QuestionRe: dimension of stl Pin
Sharjith23-Jul-07 6:51
memberSharjith23-Jul-07 6:51 
AnswerRe: dimension of stl [modified]-pls i need ur help Pin
saisp24-Jul-07 17:28
membersaisp24-Jul-07 17:28 
QuestionProblem Building Pin
dspantha29-Jan-07 15:54
memberdspantha29-Jan-07 15:54 
vickys24-Jan-07 12:42
membervickys24-Jan-07 12:42 
vickys24-Jan-07 12:42
membervickys24-Jan-07 12:42 
tulip.sun7-Feb-07 22:45
membertulip.sun7-Feb-07 22:45 
Questiontrouble building Pin
mea3616-Jan-07 7:31
membermea3616-Jan-07 7:31 
QuestionI am very interested in the topological relation of triangles [modified] Pin
hyzhujc4-Dec-06 20:38
memberhyzhujc4-Dec-06 20:38 
AnswerRe: I am very interested in the topological relation of triangles Pin
Sharjith18-Dec-06 4:15
memberSharjith18-Dec-06 4:15 
GeneralNC & RP code Pin
harshalmsrsas19-Nov-06 23:14
memberharshalmsrsas19-Nov-06 23:14 
AnswerRe: NC & RP code Pin
Sharjith18-Dec-06 4:07
memberSharjith18-Dec-06 4:07 
GeneralI want to use OpenGL with STL From Robotic 6 axis Pin
aluntum15-Feb-06 9:25
memberaluntum15-Feb-06 9:25 
QuestionI can't load other stl file Pin
qinhongxian19-Dec-05 6:24
memberqinhongxian19-Dec-05 6:24 
GeneralSlow and Selection should disabled out of the stl object Pin
lua8-Jun-05 1:03
memberlua8-Jun-05 1:03 

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