OpenSCAD User Manual/STL Import and Export

STL Import and Export

A prime ingredient of any 3D design flow is the ability to import from and export to other tools. The STL file format is currently the most common format used.

STL Import

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import_stl

Imports an STL file for use in the current OpenSCAD model

Parameters

"<file name>" 

A string containing the path to the STL file to include. Double-quotes are required.

convexity

Integer. The convexity parameter specifies the maximum number of front sides (back sides) a ray intersecting the object might penetrate. This parameter is only needed for correctly displaying the object in OpenCSG preview mode and has no effect on the polyhedron rendering.

Usage examples:

import_stl("example012.stl", convexity = 5);

STL Export

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STL Export

To export your design, select "Export as STL..." from the "Design" menu, then enter a filename in the ensuing dialog box. Don't forget to add the ".stl" extension.

Trouble shooting:

After compile and render GCAL (F6), you may see that your design is simple: no. That's bad news.

See line 8 in the following output from OpenSCAD 2010.02:

Parsing design (AST generation)...
Compiling design (CSG Tree generation)...
Compilation finished.
Rendering Polygon Mesh using CGAL...
Number of vertices currently in CGAL cache: 732
Number of objects currently in CGAL cache: 12
   Top level object is a 3D object:
   Simple:         no
   Valid:         yes
   Vertices:       22
   Halfedges:      70
   Edges:          35
   Halffacets:     32
   Facets:         16
   Volumes:         2
Total rendering time: 0 hours, 0 minutes, 0 seconds
Rendering finished.

When you try to export this to .STL you will get a message like:

Object isn't a valid 2-manifold! Modify your design..

"Manifold" means that it is "water tight" and that there are no holes in the geometry. In a valid 2-manifold each edge must connect exactly two facets. That means that the program must be able to connect a face with an object. E.g. if you use a cube of height 10 to carve out something from a wider of cube of height 10, it is not clear to which cube the top or the bottom belongs. So make the small extracting cube a bit "longer" (or "shorter"):

difference() {
        // original
        cube (size = [2,2,2]);
        // object that carves out
        # translate ([0.5,0.5,-0.5]) {
            cube (size = [1,1,3]);     
        }
}

Correct use of difference

Here is a more tricky little example taken from the OpenSCAD Forum (retrieved 15:13, 22 March 2010 (UTC)):

module example1() {
                cube([20, 20, 20]);
                translate([-20, -20, 0]) cube([20, 20, 20]);
                cube([50, 50, 5], center = true);
        }
module example2() {
                cube([20.1, 20.1, 20]);
                translate([-20, -20, 0]) cube([20.1, 20.1, 20]);
                cube([50, 50, 5], center = true);
        }

Example1 would render like this:

A not valid 2-manifold cube (simple = no)

The example1 module is not a valid 2-manifold because both cubes are sharing one edge. They touch each other but do not intersect.

Example2 is a valid 2-manifold because there is an intersection. Now the each edge must connect exactly two facets constraints of 2-manifolds is is met.

Pieces you are subtracting must extend past the original part. (OpenSCAD Tip: Manifold Space and Time, retrieved 18:40, 22 March 2010 (UTC)).