prosperon/scripts/spline.js

var Spline = {};
Spline.sample_angle = function (type, points, angle) {
  if (type === 0) return spline.catmull(points, angle);
  else if (type === 1) return spline.bezier(points, angle);
  return undefined;
};

Spline.bezier_loop = function (cp) {
  cp.push(Vector.reflect_point(cp.at(-2), cp.at(-1)));
  cp.push(Vector.reflect_point(cp[1], cp[0]));
  cp.push(cp[0].slice());
  return cp;
};

Spline.bezier_node_count = function (cp) {
  if (cp.length === 4) return 2;
  return 2 + (cp.length - 4) / 3;
};

Spline.is_bezier = function (t) {
  return t === Spline.type.bezier;
};
Spline.is_catmull = function (t) {
  return t === Spline.type.catmull;
};

Spline.bezier2catmull = function (b) {
  var c = [];
  for (var i = 0; i < b.length; i += 3) c.push(b[i]);
  return c;
};

Spline.catmull2bezier = function (c) {
  var b = [];
  for (var i = 1; i < c.length - 2; i++) {
    b.push(c[i].slice());
    b.push(
      c[i + 1]
        .sub(c[i - 1])
        .scale(0.25)
        .add(c[i]),
    );
    b.push(
      c[i]
        .sub(c[i + 2])
        .scale(0.25)
        .add(c[i + 1]),
    );
  }
  b.push(c[c.length - 2]);
  return b;
};

Spline.catmull_loop = function (cp) {
  cp = cp.slice();
  cp.unshift(cp.last());
  cp.push(cp[1]);
  cp.push(cp[2]);
  return cp;
};

Spline.catmull_caps = function (cp) {
  if (cp.length < 2) return;
  cp = cp.slice();
  cp.unshift(cp[0].sub(cp[1]).add(cp[0]));
  cp.push(cp.last().sub(cp.at(-2).add(cp.last())));
  return cp;
};

Spline.catmull_caps.doc = "Given a set of control points cp, return the necessary caps added to the spline.";

Spline.catmull2bezier.doc = "Given a set of control points C for a camtull-rom type curve, return a set of cubic bezier points to give the same curve.";

Spline.type = {
  catmull: 0,
  bezier: 1,
  bspline: 2,
  cubichermite: 3,
};

Spline.bezier_tan_partner = function (points, i) {
  if (i % 3 === 0) return undefined;
  var partner_i = i % 3 === 2 ? i - 1 : i + 1;
  return points[i];
};

Spline.bezier_cp_mirror = function (points, i) {
  if (i % 3 === 0) return undefined;
  var partner_i = i % 3 === 2 ? i + 2 : i - 2;
  var node_i = i % 3 === 2 ? i + 1 : i - 1;
  if (partner_i >= points.length || node_i >= points.length) return;
  points[partner_i] = points[node_i].sub(points[i]).add(points[node_i]);
};

Spline.bezier_point_handles = function (points, i) {
  if (!Spline.bezier_is_node(points, i)) return [];
  var a = i - 1;
  var b = i + 1;
  var c = [];
  if (a > 0) c.push(a);

  if (b < points.length) c.push(b);

  return c;
};

Spline.bezier_nodes = function (points) {
  var c = [];
  for (var i = 0; i < points.length; i += 3) c.push(points[i].slice());

  return c;
};

Spline.bezier_is_node = function (points, i) {
  return i % 3 === 0;
};
Spline.bezier_is_handle = function (points, i) {
  return !Spline.bezier_is_node(points, i);
};

return { Spline };