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Fix buffer optimization for inverted rings #878

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merged 1 commit into from
May 31, 2022
Merged

Fix buffer optimization for inverted rings #878

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8 changes: 5 additions & 3 deletions modules/core/src/main/java/org/locationtech/jts/operation/buffer/BufferCurveSetBuilder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -307,6 +307,7 @@ private void addRingSide(Coordinate[] coord, double offsetDistance, int side, in
}

private static final int MAX_INVERTED_RING_SIZE = 9;
private static final int INVERTED_CURVE_VERTEX_FACTOR = 4;
private static final double NEARNESS_FACTOR = 0.99;

/**
Expand Down Expand Up @@ -344,10 +345,11 @@ private static boolean isRingCurveInverted(Coordinate[] inputPts, double distanc
if (inputPts.length >= MAX_INVERTED_RING_SIZE) return false;

/**
* An inverted curve has no more points than the input ring.
* This also eliminates concave inputs (which will produce fillet arcs)
* Don't check curves which are much larger than the input.
* This improves performance by avoiding checking some concave inputs
* (which can produce fillet arcs with many more vertices)
*/
if (curvePts.length > inputPts.length) return false;
if (curvePts.length > INVERTED_CURVE_VERTEX_FACTOR * inputPts.length) return false;

/**
* Check if the curve vertices are all closer to the input ring
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11 changes: 11 additions & 0 deletions modules/core/src/test/java/org/locationtech/jts/operation/buffer/BufferTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -565,6 +565,17 @@ public void testMultiPolygonElementRemoved() {
checkBufferNumGeometries(wkt, -18, 1);
}

/**
* Checks a bug in the inverted-ring-removal heuristic.
* See https://github.com/locationtech/jts/issues/876
*/
public void testLineClosedNoHole() {
String wkt = "LINESTRING (-20 0, 0 20, 20 0, 0 -20, -20 0)";
checkBufferHasHole(wkt, 70, false);
}

//===================================================

private void checkBufferEmpty(String wkt, double dist, boolean isEmptyExpected) {
Geometry a = read(wkt);
Geometry result = a.buffer(dist);
Expand Down