Introduction

Pathbuilder is a tool for openSCAD that make the creation of complex 2D shapes easier with a syntax similar to the one used for svg path. Pathbuilder supports the complete svg command set and several extra commands to make the creation of 2d shapes as easy as possible.

You can place fillets or Chamfers at any point. Extend lines up to an arbitrary boundary and much more.

Installation

Although this library has grown to three code units, Pathbuilder is contained in a single .scad file and in has no dependencies on other libraries. Just copy pathbuilder.scad to your openSCAD library folder and put

use <pathbuilder.scad>

at the top of your code unit and you are ready to go. Copy this code into a new blank openSCAD file to make sure it all works. Dont forget to check out the demo folder it contains 6 examples on how Pathbuilder can be used.

Quick test

include <pathbuilder.scad>

svgShape("m 0 0chamfer8h20fillet2v20fillet10h20v-10fillet2l35 20fillet2l-35 20fillet2v-10h-40fillet30", $fn=32);

Note that you can always add $fn or other global openSCAD parameters exclusivly into any function or module. You should see this.

flexible

There are two ways to use pathbuilder. You can use a normal svg path string in Pathbuilder. This means that you can also draw your shapes in vector drawing programs such as inkscape and copy the path string into Pathbuilder.

However the power of openSCAD is of course in its parametric capabilities. Although you could string together a svg path string with some variables, it isn't exactly elegant.

Pathbuilder also offers access to every command directly in your code. Commands are simply chained just like you are used to with openSCAD. A polygon is drawn at the end of the command sequence. This way you can pass your parameters directly into pathbuilder commands.

In the above example I used pathbuilder to generate complex ship hull shapes. Here I made extensive use of the svgPoints() function which returns a list of coordinates rather than letting pathbuilder produce the polygon. The points are then processed to produce the polyhedron in the picture. The mesh is perfect and my 3D printer slicer didn't report any issues.

S bracket example

code

use <pathbuilder.scad>

//  S bracket

width = 40;
length = 60;
height = 30;
thickness = 5;
inner_radius = 3;

$fn = 64;
linear_extrude(width){
    m(0,0)
    v(thickness)
    h((length - thickness)/2)
    fillet(inner_radius)
    V(height)
    fillet(inner_radius + thickness)
    H(length)
    v(-thickness)
    h(-(length - thickness)/2)
    fillet(inner_radius)
    V(0)
    fillet(inner_radius + thickness)
    H(0);
}

Each method has its own benefits and drawbacks. The SVG path string method can create a polygon or return a point list which you can manipulate as desired. But modules also allow a much finer control over the curve segmentation as you can slip in a $fa, $fs or $fn parameter with every command module.

Rip and pillage

If Pathbuilder isn't quite your thing you might still was to have a look at some of the functions. Pathbuilder has no dependencies and the functions have been written as self contained as possible and sensible. Even easier is to jump over to my other repository of stand-alone ready to use openSCAD functions called openSCAD_functions

Here are just a few examples:

function curveBetweenPoints(pt1, pt2, radius, incl_start_pt = true)

Returns a list of points representing the shortest curve between two points with a given radius.

function fillet(pts, index, radius)

Returns a list of points representing an arc with a given radius that is the tangent to pt1 and pt2 also known as a fillet.

function chamfer(pts, index, size)

Returns two points for a nice balanced symetrical chamfer of size for a given point in the point list.

Command overview

Here is a quick overview of the commands implemented so far. Check out the detailed command documentation in the wiki

Most path commands have an uppercase and a lowercase version in Pathbuilder. This is an important distriction because the case defines if the command works in absolute coordinates (Uppercase) or relative (lowercase) from the current point. More about this in the wiki. In this overview I ignore the details case has on the commands.

High level commands

When using the SVG path syntax in string format you will need to call a function to have the commands in the string processed. The main two are at the top of this list. The other three are more useful as debugging tools.

Checkout pathbuilderdemo.scad demo 3 which shows a third way to interpret process the svg path string. Here three separate steps are taken to go from path string to 2D point list.

    pb_swoosh = "M68.56-4L18.4-25.36Q12.16-28 7.92-28q-4.8 0-6.96 3.36-1.36 2.16-.8 5.48t2.96 7.08q2 3.04 6.56 8-1.6-2.56-2.24-5.28-1.2-5.12 2.16-7.52Q11.2-18 14-18q2.24 0 5.04 .72z";
    cmds = pb_tokenizeSvgPath(pb_swoosh);
    data = pb_processCommands(cmds);
    pts_list = pb_postProcessPathLists(data);
    pts = pts_list[0];
    polygon(pts);

SVG Commands:

The commands in this table should be fully compliant with the SVG path syntax.

Example of using the forward command with a polyline boundary

Extra path commands:

These are extra commands introduced by Pathbuilder. The command set is not settled yet. In fact, only fillet and chamfer are likely to remain as they are. angle, polar and forward could be rolled into a single command.