Merge pull request #3 from momentumworks/master

Use binary search in t2length() and explicitly check for null and undefined in Bezier function

build/path-properties.js

@@ -1,4 +1,4 @@
-// http://geoexamples.com/path-properties/ Version 0.1.1. Copyright 2016 Roger Veciana i Rovira.
+// http://geoexamples.com/path-properties/ Version 0.1.1. Copyright 2017 Roger Veciana i Rovira.
 (function (global, factory) {
 	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
 	typeof define === 'function' && define.amd ? define(['exports'], factory) :
@@ -58,7 +58,7 @@ function Bezier$1(ax, ay, bx, by, cx, cy, dx, dy) {
   this.c = {x:cx, y:cy};
   this.d = {x:dx, y:dy};
 
-  if(dx && dy){
+  if(dx !== null && dx !== undefined && dy !== null && dy !== undefined){
     this.getArcLength = getCubicArcLength;
     this.getPoint = cubicPoint;
     this.getDerivative = cubicDerivative;
@@ -145,13 +145,24 @@ function cubicDerivative(xs, ys, t){
 function t2length(length, total_length, func, xs, ys){
   var error = 1;
   var t = length/total_length;
-
-  while (error > 0.008){
-
-    var calcLength = func(xs, ys, t);
-    error = Math.abs(length - calcLength)/total_length;
-    t = t + (length-calcLength)/total_length;
+  var step = (length - func(xs, ys, t))/total_length;
+
+  while (error > 0.001){
+    var increasedTLength = func(xs, ys, t + step);
+    var decreasedTLength = func(xs, ys, t - step);
+    var increasedTError = Math.abs(length - increasedTLength)/total_length;
+    var decreasedTError = Math.abs(length - decreasedTLength)/total_length;
+    if (increasedTError < error) {
+      error = increasedTError;
+      t += step;
+    } else if (decreasedTError < error) {
+      error = decreasedTError;
+      t -= step;
+    } else {
+      step /= 2;
+    }
   }
+
   return t;
 }