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fix is convex negated (#241)
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@msbarry
msbarry authored May 30, 2022
1 parent 27cf19c commit f93e522
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Showing 2 changed files with 34 additions and 22 deletions.
11 changes: 10 additions & 1 deletion planetiler-core/src/main/java/com/onthegomap/planetiler/geo/GeoUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -403,11 +403,20 @@ public static Polygon createPolygon(LinearRing exteriorRing, List<LinearRing> ri
return JTS_FACTORY.createPolygon(exteriorRing, rings.toArray(LinearRing[]::new));
}


/**
* Returns {@code true} if the signed area of the triangle formed by 3 sequential points changes sign anywhere along
* Returns {@code false} if the signed area of the triangle formed by 3 sequential points changes sign anywhere along
* {@code ring}, ignoring repeated and collinear points.
*/
public static boolean isConvex(LinearRing ring) {
return !isConcave(ring);
}

/**
* Returns {@code true} if the signed area of the triangle formed by 3 sequential points changes sign anywhere along
* {@code ring}, ignoring repeated and collinear points.
*/
public static boolean isConcave(LinearRing ring) {
CoordinateSequence seq = ring.getCoordinateSequence();
if (seq.size() <= 3) {
return false;
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45 changes: 24 additions & 21 deletions planetiler-core/src/test/java/com/onthegomap/planetiler/geo/GeoUtilsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,7 @@ void testMetersPerPixel(int zoom, double meters) {

@Test
void testIsConvexTriangle() {
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
0, 1,
Expand All @@ -127,7 +127,7 @@ void testIsConvexTriangle() {

@Test
void testIsConvexRectangle() {
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
Expand All @@ -138,21 +138,21 @@ void testIsConvexRectangle() {

@Test
void testBarelyConvexRectangle() {
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
0.5, 0.5,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
0.4, 0.4,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
Expand All @@ -163,39 +163,39 @@ void testBarelyConvexRectangle() {

@Test
void testConcaveRectangleDoublePoints() {
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
0, 0,
1, 0,
1, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 0,
1, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
1, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
0, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
Expand All @@ -207,7 +207,7 @@ void testConcaveRectangleDoublePoints() {

@Test
void testBarelyConcaveRectangle() {
assertConvex(false, newLinearRing(
assertConcave(false, newLinearRing(
0, 0,
1, 0,
1, 1,
Expand All @@ -218,31 +218,31 @@ void testBarelyConcaveRectangle() {

@Test
void test5PointsConcave() {
assertConvex(false, newLinearRing(
assertConcave(false, newLinearRing(
0, 0,
0.5, 0.1,
1, 0,
1, 1,
0, 1,
0, 0
));
assertConvex(false, newLinearRing(
assertConcave(false, newLinearRing(
0, 0,
1, 0,
0.9, 0.5,
1, 1,
0, 1,
0, 0
));
assertConvex(false, newLinearRing(
assertConcave(false, newLinearRing(
0, 0,
1, 0,
1, 1,
0.5, 0.9,
0, 1,
0, 0
));
assertConvex(false, newLinearRing(
assertConcave(false, newLinearRing(
0, 0,
1, 0,
1, 1,
Expand All @@ -254,31 +254,31 @@ void test5PointsConcave() {

@Test
void test5PointsColinear() {
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
0.5, 0,
1, 0,
1, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 0.5,
1, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
0.5, 1,
0, 1,
0, 0
));
assertConvex(true, newLinearRing(
assertConcave(true, newLinearRing(
0, 0,
1, 0,
1, 1,
Expand All @@ -288,14 +288,17 @@ void test5PointsColinear() {
));
}

private static void assertConvex(boolean isConvex, LinearRing ring) {
private static void assertConcave(boolean isConcave, LinearRing ring) {
for (double rotation : new double[]{0, 90, 180, 270}) {
LinearRing rotated = (LinearRing) AffineTransformation.rotationInstance(Math.toRadians(rotation)).transform(ring);
for (boolean flip : new boolean[]{false, true}) {
LinearRing flipped = flip ? (LinearRing) AffineTransformation.scaleInstance(-1, 1).transform(rotated) : rotated;
for (boolean reverse : new boolean[]{false, true}) {
LinearRing reversed = reverse ? flipped.reverse() : flipped;
assertEquals(isConvex, isConvex(reversed), "rotation=" + rotation + " flip=" + flip + " reverse=" + reverse);
assertEquals(isConcave, isConcave(reversed),
"rotation=" + rotation + " flip=" + flip + " reverse=" + reverse);
assertEquals(!isConcave, isConvex(reversed),
"rotation=" + rotation + " flip=" + flip + " reverse=" + reverse);
}
}
}
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