MacroMachines/extrude

turn a 2d shape into 3d with extrusion

extrude

Use extrusion to turn a 2d shape into a 3d mesh. Extrusion is the process of "pulling" a 2d shape through space to make it 3d. This module contains a single function that accepts a collection of 2d points, and returns a 3d mesh in the form of a simplicial complex, a data structure that works well with the stack.gl ecosystem. The implementation uses seidel's algorithm to triangulate the top and bottom faces, and simple triangulated rectangles for the sides.

View a demo.

install

To use in your project

npm install extrude

To see an example, clone this repo, then call

npm install
npm start

and it should open a browser with a floating square. You can also try

npm run demo

for a demo with several shapes.

example

Assuming you already have a stack.gl context gl, make a cube like this!

var extrude = require('extrude')

var points = [[-1, -1], [1, -1], [1, 1], [-1, 1]]
var cube = extrude(points, {bottom: -1, top: 1})

var geometry = require('gl-geometry')(gl)
geometry.attr('position', cube.positions)
geometry.faces(cube.cells)

See example.js for a complete end-to-end example.

usage

complex = extrude(points, opts)

Create a simplicial complex from a set of points.

points should be a list in the form [[x, y], [x, y], ...]

complex has two attributes:

• complex.position : array of 3d vertices [[x, y, z], [x, y, z], ...]
• complex.cells : array of tuples that index into the vertices [[i, j, k], [i, j, k], ...]

opts can include the following options:

• opts.bottom : bottom of the extruded object default: 0
• opts.top : top of the extruded object default: 1
• opts.closed : whether to close the top and bottom of the mesh default: true

If top and bottom are equal it will result in a single-sided 3d surface.