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  1. PO
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    <p>So, since I was unable to find anything like this on the web, I written my own algorithm.</p> <p>It may be insanely ineffective, but it works fast enough for me.</p> <p>Here it goes:</p> <pre><code>/** * Takes a polygon, defined by a list of lines, and splits it into several * paths on points of intersection. If non-self-intersected path is passed in, * the same path is returned. * @param path * @return */ public static List&lt;List&lt;Line2D&gt;&gt; splitPath(List&lt;Line2D&gt; lines) { List&lt;List&lt;Line2D&gt;&gt; splitted = new ArrayList&lt;List&lt;Line2D&gt;&gt;(); // find intersections. loop1: for (Line2D l1 : lines) { for (Line2D l2 : lines) { if (l1 == l2) continue; Point2D intr; if ((intr = linesIntersect(l1, l2)) != null) { // creating two splitted subpaths int i1 = lines.indexOf(l1); int i2 = lines.indexOf(l2); List&lt;Line2D&gt; subpath1 = new ArrayList&lt;Line2D&gt;(); subpath1.addAll(lines.subList(0, i1)); subpath1.add(new Line2D.Double(l1.getP1(), intr)); subpath1.add(new Line2D.Double(intr, l2.getP2())); subpath1.addAll(lines.subList(i2 + 1, lines.size())); splitted.addAll(splitPath(subpath1)); List&lt;Line2D&gt; subpath2 = new ArrayList&lt;Line2D&gt;(); subpath2.add(new Line2D.Double(intr, l1.getP2())); subpath2.addAll(lines.subList(i1 + 1, i2)); subpath2.add(new Line2D.Double(l2.getP1(), intr)); splitted.addAll(splitPath(subpath2)); break loop1; } } } if (splitted.size() &gt; 0) { return splitted; } else { return Collections.singletonList(lines); } } /** * Returns point of intersection of this line segments. * @param l1 * @param l2 * @return */ public static Point2D linesIntersect(Line2D l1, Line2D l2) { if (l1.getP1().equals(l2.getP2()) || l1.getP2().equals(l2.getP1())) return null; Point2D inter = lineIntersection(l1, l2); if (inter == null) return null; double infS = HEADER.infS; double x = inter.getX(); if (((l1.getX1() &gt; l1.getX2()) ? (x + infS &gt; l1.getX2() &amp;&amp; x - infS &lt; l1.getX1()) : (x - infS &lt; l1.getX2() &amp;&amp; x + infS &gt; l1.getX1())) &amp;&amp; ((l2.getX1() &gt; l2.getX2()) ? (x + infS &gt; l2.getX2() &amp;&amp; x - infS &lt; l2.getX1()) : (x - infS &lt; l2.getX2() &amp;&amp; x + infS &gt; l2.getX1()))) { return inter; } else { return null; } } /** * Returns point of lines intersection, or null if they are parallel. * @param l1 * @param l2 * @return */ public static Point2D lineIntersection(Line2D l1, Line2D l2) { double a1 = l1.getY2() - l1.getY1(); double b1 = l1.getX1() - l1.getX2(); double c1 = a1*l1.getX1() + b1*l1.getY1(); double a2 = l2.getY2() - l2.getY1(); double b2 = l2.getX1() - l2.getX2(); double c2 = a2*l2.getX1() + b2*l2.getY1(); double det = a1*b2 - a2*b1; if (det != 0) { double x = (b2*c1 - b1*c2)/det; double y = (a1*c2 - a2*c1)/det; return new Point2D.Double(x, y); } else { // lines are parallel return null; } } </code></pre>
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    1. POAlgorithm to split self-intersected Path2D into several not self-intersected paths?
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    1. USRogach
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    1. COI have been looking at this issue too - I suspect you algorithm does not handle secondary intersections (If there is an intersection between subpath1 and subpath2
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    2. COYes, I missed that. I'll think of a better algorithm. Thanks for noticing!
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