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Apr 16, 2019
Aug 1, 2017


The Belfry OpenScad Library - A library of tools, shapes, and helpers to make OpenScad easier to use.

This library is a set of useful tools, shapes and manipulators that I developed while working on various projects, including large ones like the Snappy-Reprap printed 3D printer.


  1. Download the .zip or .tar.gz release file for this library.
  2. Unpack it. It should create a BOSL-v1.0 directory with the library files within it.
  3. Rename the directory to BOSL.
  4. Move the BOSL directory into the apropriate OpenSCAD library directory for your platform:
    • Windows: My Documents\OpenSCAD\libraries\
    • Linux: $HOME/.local/share/OpenSCAD/libraries/
    • Mac OS X: $HOME/Documents/OpenSCAD/libraries/
  5. Restart OpenSCAD.


For purposes of the BOSL library, the following terms apply:

  • Left: Towards X-

  • Right: Towards X+

  • Front/Forward: Towards Y-

  • Back/Behind: Towards Y+

  • Bottom/Down/Below: Towards Z-

  • Top/Up/Above: Towards Z+

  • Axis-Positive: Towards the positive end of the axis the object is oriented on. IE: X+, Y+, or Z+.

  • Axis-Negative: Towards the negative end of the axis the object is oriented on. IE: X-, Y-, or Z-.

Common Arguments:

Args What it is
fillet Radius of rounding for interior or exterior edges.
chamfer Size of chamfers/bevels for interior or exterior edges.
orient Axis a part should be oriented along. Given as an XYZ triplet of rotation angles. It is recommended that you use the ORIENT_ constants from constants.scad. Default is usually ORIENT_Z for vertical orientation.
align Side of the origin that the part should be on. Given as a vector away from the origin. It is recommended that you use the V_ constants from constants.scad. Default is usually V_ZERO for centered.


A lot of the features of this library are to allow shorter, easier-to-read, intent-based coding. For example:

BOSL/transforms.scad Examples Raw OpenSCAD Equivalent
up(5) translate([0,0,5])
xrot(30,cp=[0,10,20]) translate([0,10,20]) rotate([30,0,0]) translate([0,-10,-20])
xspread(20,n=3) for (dx=[-20,0,20]) translate([dx,0,0])
zring(n=6,r=20) for (zr=[0:5]) rotate([0,0,zr*60]) translate([20,0,0])
skew_xy(xa=30,ya=45) multmatrix([[1,0,tan(30),0],[0,1,tan(45),0],[0,0,1,0],[0,0,0,1]])
BOSL/shapes.scad Examples Raw OpenSCAD Equivalent
upcube([10,20,30]); translate([0,0,15]) cube([10,20,30], center=true);
cuboid([20,20,30], fillet=5, edges=EDGES_Z_ALL); minkowski() {cube([10,10,20], center=true); sphere(r=5, $fn=32);}
prismoid([30,40],[20,30],h=10); hull() {translate([0,0,0.005]) cube([30,40,0.01], center=true); translate([0,0,9.995]) cube([20,30,0.01],center=true);}
xcyl(l=20,d=4); rotate([0,90,0]) cylinder(h=20, d=4, center=true);
cyl(l=100, d=40, fillet=5); translate([0,0,50]) minkowski() {cylinder(h=90, d=30, center=true); sphere(r=5);}
BOSL/masks.scad Examples Raw Openscad Equivalent
chamfer_mask_z(l=20,chamfer=5); rotate(45) cube([5*sqrt(2), 5*sqrt(2), 20], center=true);
fillet_mask_z(l=20,fillet=5); difference() {cube([10,10,20], center=true); for(dx=[-5,5],dy=[-5,5]) translate([dx,dy,0]) cylinder(h=20.1, r=5, center=true);}
fillet_hole_mask(r=30,fillet=5); difference() {cube([70,70,10], center=true); translate([0,0,-5]) rotate_extrude(convexity=4) translate([30,0,0]) circle(r=5);}

The Library Files

The library files are as follows:

Commonly Used

  • transforms.scad: The most commonly used transformations, manipulations, and shortcuts are in this file.
  • shapes.scad: Common useful shapes and structured objects.
  • masks.scad: Shapes that are useful for masking with difference() and intersect().
  • threading.scad: Modules to make triangular and trapezoidal threaded rods and nuts.
  • paths.scad: Functions and modules to work with arbitrary 3D paths.
  • beziers.scad: Functions and modules to work with bezier curves.

Standard Parts



The full library docs can be found at