example.js

var bunny = require('bunny');
var simplify = require('mesh-simplify')

var orient = require('./index');
var normals = require('normals');

// to go slightly faster
bunny = simplify(bunny.cells, bunny.positions)(1000)
var cells = bunny.cells
var positions = bunny.positions
// Make mesh triangle soup to test global checking
var duplicatedPositions = []
var duplicatedCells = []
var currentIndex = 0
cells.map(function(cell) {
  duplicatedPositions.push(positions[cell[0]])
  duplicatedPositions.push(positions[cell[1]])
  duplicatedPositions.push(positions[cell[2]])
  duplicatedCells.push([currentIndex, currentIndex + 1, currentIndex + 2])
  currentIndex += 3
})
cells = duplicatedCells
positions = duplicatedPositions

var flipCount = 0;
var cells = cells.map(function(cell, cellIndex) {
  if (Math.random() >= 0.5) {
    // flip orientation
    flipCount++;
    return [cell[1], cell[0], cell[2]];
  } else {
    return cell;
  }
});

console.log('flipped', flipCount, 'cells');
console.time('orient');
console.log('reflipped', orient(cells, positions, cells.length * 2, 3));
console.timeEnd('orient');

var regl = require('regl')()
var mat4 = require('gl-mat4')
var wire = require('gl-wireframe')
var camera = require('regl-camera')(regl, {
  center: [0, 0, 0],
  theta: Math.PI / 2,
  distance: 4
})

var drawWires = regl({
  vert: `
  precision mediump float;
  attribute vec3 position, normal;
  varying vec3 vNorm;
  uniform mat4 projection;
  uniform mat4 view;
  void main() {
    vNorm = normal;
    gl_Position = projection * view * vec4(position, 1.0);
  }
  `, frag: `
  precision mediump float;
  varying vec3 vNorm;
  void main() {
    vec3 lightDir = normalize(vec3(1., 1., 0.));
    gl_FragColor = vec4(vec3(0.6) + dot(vNorm, lightDir), 1.0);
  }
  `,
  attributes: {
    position: positions,
    normal: normals.vertexNormals(cells, positions)
  },
  elements: wire(cells),
  primitive: 'lines'
})

var faceNormals = normals.faceNormals(cells, positions)
var explodedPositions = [];
var perVertexFaceNormals = [];
cells.map(function(cell, i) {
  explodedPositions.push(positions[cell[0]]);
  explodedPositions.push(positions[cell[1]]);
  explodedPositions.push(positions[cell[2]]);
  perVertexFaceNormals.push(faceNormals[i]);
  perVertexFaceNormals.push(faceNormals[i]);
  perVertexFaceNormals.push(faceNormals[i]);
});

var drawOuter = regl({
  vert: `
  precision mediump float;

  attribute vec3 position, normal;
  varying vec3 vNorm;
  uniform mat4 projection;
  uniform mat4 view;
  void main() {
    vNorm = normal;
    gl_Position = projection * view * vec4(position, 1.0);
  }
  `
  , frag: `
  precision mediump float;
  varying vec3 vNorm;
  void main() {
    vec3 lightDir = normalize(vec3(1., 1., 0.));
    gl_FragColor = vec4(vNorm, 1.0);
  }
  `,
  attributes: {
    position: explodedPositions,
    normal: perVertexFaceNormals
  },
  count: cells.length * 3,
  primitive: 'triangles'
})

regl.frame(() => {
  regl.clear({
    color: [1, 1, 1, 1],
    depth: 1
  })
  camera(() => {
    drawWires({
      view: mat4.create()
    })
    drawOuter({
      view: mat4.create()
    })
  })
})