From 0d41e0f84676170d4a9381f2ad0cc250d8bf6bf9 Mon Sep 17 00:00:00 2001
From: Max Gaukler <development@maxgaukler.de>
Date: Thu, 27 Dec 2012 01:51:25 +0100
Subject: [PATCH] added inside-first vector sorting (heuristic simple
algorithm)
---
.../liblasercut/utils/VectorOptimizer.java | 176 +++++++++++++++++-
1 file changed, 174 insertions(+), 2 deletions(-)
diff --git a/src/com/t_oster/liblasercut/utils/VectorOptimizer.java b/src/com/t_oster/liblasercut/utils/VectorOptimizer.java
index e66a451..7a99999 100644
--- a/src/com/t_oster/liblasercut/utils/VectorOptimizer.java
+++ b/src/com/t_oster/liblasercut/utils/VectorOptimizer.java
@@ -4,6 +4,9 @@ import com.t_oster.liblasercut.LaserProperty;
import com.t_oster.liblasercut.VectorCommand;
import com.t_oster.liblasercut.VectorPart;
import com.t_oster.liblasercut.platform.Point;
+import com.t_oster.liblasercut.platform.Rectangle;
+import java.util.Collections;
+import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;
@@ -16,8 +19,8 @@ public class VectorOptimizer
public enum OrderStrategy
{
FILE,
- //INNER_FIRST,
- NEAREST
+ NEAREST,
+ INNER_FIRST
}
class Element
@@ -39,11 +42,42 @@ public class VectorOptimizer
moves = inv;
}
}
+
+
+
Point getEnd()
{
return moves.isEmpty() ? start : moves.get(moves.size()-1);
}
+
+ /**
+ * compute bounding box of moves, including start point
+ * @return Rectangle
+ */
+ Rectangle boundingBox() {
+ if (start == null) { // TODO may this happen?
+ return null;
+ }
+ Rectangle bb=new Rectangle(start.x,start.y,start.x,start.y);
+ for (Point p: moves) {
+ bb.add(p);
+ }
+ return bb;
+ }
+
+ /**
+ * test if this Element represents a closed path (polygon)
+ * @return true if start equals end, false otherwise
+ */
+ boolean isClosedPath() {
+ if ((start == null) || moves.isEmpty()) {
+ return false;
+ }
+ return getEnd().equals(start);
+ }
}
+
+
private OrderStrategy strategy = OrderStrategy.FILE;
@@ -166,6 +200,144 @@ public class VectorOptimizer
}
break;
}
+ case INNER_FIRST: {
+ /** cut inside parts first, outside parts later
+ * this algorithm is very robust, it works even for unconnected paths that are split into individual lines (e.g. from some DXF imports)
+ * it is not completely perfect, as it only considers the bounding-box and not the individual path
+ *
+ * see below for documentation of the inner workings
+ */
+
+ // helper classes:
+ abstract class ElementValueComparator implements Comparator<Element> {
+ /**
+ * get one integer from the element
+ * order ascending by this integer
+ * inside objects should have the lowest values
+ */
+ abstract int getValue(Element e);
+
+ /**
+ * compare by getValue()
+ */
+ @Override
+ public int compare(Element a, Element b) {
+ Integer av = new Integer(getValue(a));
+ Integer bv = new Integer(getValue(b));
+ return av.compareTo(bv);
+ }
+
+ }
+
+ class XMinComparator extends ElementValueComparator {
+ // compare by XMin a>b
+ @Override
+ int getValue(Element e) {
+ return -e.boundingBox().getXMin();
+ }
+ }
+
+ class YMinComparator extends ElementValueComparator {
+ // compare by YMin a>b
+ @Override
+ int getValue(Element e) {
+ return -e.boundingBox().getYMin();
+ }
+ }
+
+ class XMaxComparator extends ElementValueComparator {
+ // compare by XMax a<b
+ @Override
+ int getValue(Element e) {
+ return e.boundingBox().getXMax();
+ }
+ }
+
+ class YMaxComparator extends ElementValueComparator {
+ // compare by YMax a<b
+ @Override
+ int getValue(Element e) {
+ return e.boundingBox().getYMax();
+ }
+ }
+ result.addAll(e);
+ /**
+ * HEURISTIC:
+ * this algorithm is based on the following observation:
+ * let I and O be rectangles, I inside O
+ * for explanations, assume that:
+ * - the X-axis goes from left to right
+ * - the Y-axis goes from bottom to top
+ *
+ * ---------------- O: outside rectangle
+ * | |
+ * | ---- |
+ * y axis | |in| I |
+ * ^ | ---- |
+ * | | |
+ * | ----------------
+ * |
+ * ------> x axis
+ *
+ * look at each border:
+ * right border: I.getXMax() < O.getXMax()
+ * left border: I.getXMin() > O.getXMin()
+ * top border: I.getYMax() < O.getYMax()
+ * bottom border: I.getYMin() > O.getYMin()
+ *
+ * If we now SORT BY ymax ASCENDING, ymin DESCENDING, xmax ASCENDING, xmin DESCENDING
+ * (higher sorting priority listed first)
+ * we get the rectangles sorted inside-out:
+ * 1. I
+ * 2. O
+ *
+ * Because we sort by four values, this still works if
+ * the two rectangles start at the same corner and have the same width,
+ * but only differ in height.
+ *
+ * If each rectangle is split into four separate lines
+ * (e.g. because of a bad DXF import),
+ * this still mostly works:
+ * 1. O: bottom line
+ * 2. I: bottom
+ * 3. I: top, left, right (both have same YMax, but top has a higher YMin)
+ * 4: O: top, left, right (both have same YMax, but top has a higher YMin)
+ *
+ * TRADEOFFS AND LIMITATIONS:
+ * This algorithm does not work for paths that have the same bounding-box
+ * (e.g. a circle inscribed to a square)
+ *
+ * For concave polygons with the same bounding-box,
+ * many simple Polygon-inside-Polygon algorithms also fail
+ * (or have a useless definition of "inside" that matches the misbehaviour):
+ * Draw a concave polygon, remove one point at a concave edge.
+ * The resulting polygon is clearly outside the original, although every edge of it is inside the original!
+ *
+ * FUTURE WORK:
+ * It would also be nice to sort intersecting polygons, where one polygon
+ * is "90% inside" and "10% outside" the other.
+ * Real-world example:_A circular hole at the border of a rectangle.
+ * Due to rounding errors, it may appear slightly outside the rectangle.
+ * Mathematically, it is neither fully inside nor fully outside, but the
+ * user clearly wants it to be counted as "inside".
+ *
+ * POSSIBLE LIBRARIES:
+ * http://sourceforge.net/projects/geom-java/
+ * http://sourceforge.net/projects/jts-topo-suite
+ *
+ * USEFUL METHODS:
+ * Element.isClosedPath()
+ */
+
+ // do the work:
+ Collections.sort(result,new XMinComparator());
+ Collections.sort(result,new YMinComparator());
+ Collections.sort(result,new XMaxComparator());
+ Collections.sort(result,new YMaxComparator());
+
+ // the result is now mostly sorted
+ // TODO somehow sort by intersecting area
+ }
}
return result;
}
--
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