extrude-polyline

Extrudes a 2D polyline with a given line thickness and the desired join/cap types. Tries to maintain visual consistency with HTML5 2D context stroking.

1var polyline = [ [25, 25], [15, 60] ]
2var stroke = require('extrude-polyline')({ 
3    thickness: 20, 
4    cap: 'square',
5    join: 'bevel',
6    miterLimit: 10
7})
8
9//builds a triangulated mesh from a polyline
10var mesh = stroke.build(polyline)

The returned mesh is a simplicial complex.

1{
2    positions: [ [x,y], [x,y] ],
3    cells: [ [a,b,c], [a,b,c] ]
4}

variable thickness

Currently, to achieve variable thickness you can provide a mapThickness function to the stroke instance before building. By default, it will simply return the current thickness.

1//create a falloff, so the thickness tapers toward the start of the path
2stroke.mapThickness = function(point, index, points) {
3    return this.thickness * index/(points.length-1)
4}.bind(stroke)

demo

Git clone, npm install, then npm run test

Usage

stroke = Extrusion([opt])

Creates a new path builder with the given settings:

• thickness the line thickness
• miterLimit the limit before miters turn into bevels; default 10
• join the join type, can be 'miter' or 'bevel' - default 'miter'
• cap the cap type, can be 'butt' or 'square' - defalut 'butt'

mesh = stroke.build(points)

Builds a stroke with the specified list of 2D points. Returns a simplicial complex.

Roadmap

Some features that could be useful to add at a later point. PRs welcome.

• round corners
• round end caps
• use consistent winding order so we don't need to disable gl.CULLING
• connecting start and end points
• optimizations for flat arrays (Float32Array) ?
• optimizations for GC (pooling, etc)
• handling anti-aliasing
• degenerate triangles or some other form of supporting disconnected lines
• unify codebase with polyline-normals

License

MIT, see LICENSE.md for details.