Function cutEdges

stackgl_modules/index.js:8965–9056

(floatPoints, edges, crossings, junctions, useColor)

// Cut edges along crossings/tjunctions
function cutEdges (floatPoints, edges, crossings, junctions, useColor) {
  var i, e

  // Convert crossings into tjunctions by constructing rational points
  var ratPoints = floatPoints.map(function(p) {
      return [
          rat(p[0]),
          rat(p[1])
      ]
  })
  for (i = 0; i < crossings.length; ++i) {
    var crossing = crossings[i]
    e = crossing[0]
    var f = crossing[1]
    var ee = edges[e]
    var ef = edges[f]
    var x = solveIntersection(
      ratVec(floatPoints[ee[0]]),
      ratVec(floatPoints[ee[1]]),
      ratVec(floatPoints[ef[0]]),
      ratVec(floatPoints[ef[1]]))
    if (!x) {
      // Segments are parallel, should already be handled by t-junctions
      continue
    }
    var idx = floatPoints.length
    floatPoints.push([ratToFloat(x[0]), ratToFloat(x[1])])
    ratPoints.push(x)
    junctions.push([e, idx], [f, idx])
  }

  // Sort tjunctions
  junctions.sort(function (a, b) {
    if (a[0] !== b[0]) {
      return a[0] - b[0]
    }
    var u = ratPoints[a[1]]
    var v = ratPoints[b[1]]
    return ratCmp(u[0], v[0]) || ratCmp(u[1], v[1])
  })

  // Split edges along junctions
  for (i = junctions.length - 1; i >= 0; --i) {
    var junction = junctions[i]
    e = junction[0]

    var edge = edges[e]
    var s = edge[0]
    var t = edge[1]

    // Check if edge is not lexicographically sorted
    var a = floatPoints[s]
    var b = floatPoints[t]
    if (((a[0] - b[0]) || (a[1] - b[1])) < 0) {
      var tmp = s
      s = t
      t = tmp
    }