JAVASCRIPT zoom.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var epsilon2 = 1e-12;
function cosh(x) {
  return ((x = Math.exp(x)) + 1 / x) / 2;
}
function sinh(x) {
  return ((x = Math.exp(x)) - 1 / x) / 2;
}
function tanh(x) {
  return ((x = Math.exp(2 * x)) - 1) / (x + 1);
}
var _default = exports.default = function zoomRho(rho, rho2, rho4) {
  // p0 = [ux0, uy0, w0]
  // p1 = [ux1, uy1, w1]
  function zoom(p0, p1) {
    var ux0 = p0[0],
      uy0 = p0[1],
      w0 = p0[2],
      ux1 = p1[0],
      uy1 = p1[1],
      w1 = p1[2],
      dx = ux1 - ux0,
      dy = uy1 - uy0,
      d2 = dx * dx + dy * dy,
      i,
      S;

    // Special case for u0 ≅ u1.
    if (d2 < epsilon2) {
      S = Math.log(w1 / w0) / rho;
      i = function (t) {
        return [ux0 + t * dx, uy0 + t * dy, w0 * Math.exp(rho * t * S)];
      };
    }

    // General case.
    else {
      var d1 = Math.sqrt(d2),
        b0 = (w1 * w1 - w0 * w0 + rho4 * d2) / (2 * w0 * rho2 * d1),
        b1 = (w1 * w1 - w0 * w0 - rho4 * d2) / (2 * w1 * rho2 * d1),
        r0 = Math.log(Math.sqrt(b0 * b0 + 1) - b0),
        r1 = Math.log(Math.sqrt(b1 * b1 + 1) - b1);
      S = (r1 - r0) / rho;
      i = function (t) {
        var s = t * S,
          coshr0 = cosh(r0),
          u = w0 / (rho2 * d1) * (coshr0 * tanh(rho * s + r0) - sinh(r0));
        return [ux0 + u * dx, uy0 + u * dy, w0 * coshr0 / cosh(rho * s + r0)];
      };
    }
    i.duration = S * 1000 * rho / Math.SQRT2;
    return i;
  }
  zoom.rho = function (_) {
    var _1 = Math.max(1e-3, +_),
      _2 = _1 * _1,
      _4 = _2 * _2;
    return zoomRho(_1, _2, _4);
  };
  return zoom;
}(Math.SQRT2, 2, 4);