Avoid unnecessary SimplePolygonXZ constructor checks to improve performance

Author: tordanik

core-jvm/src/test/java/org/osm2world/math/shapes/SimplePolygonXZTest.java

@@ -3,8 +3,8 @@
 import static java.lang.Math.sqrt;
 import static java.util.Arrays.asList;
 import static org.junit.Assert.*;
-import static org.osm2world.math.shapes.SimplePolygonXZ.isSelfIntersecting;
 import static org.osm2world.math.VectorXZ.NULL_VECTOR;
+import static org.osm2world.math.shapes.SimplePolygonXZ.isSelfIntersecting;
 import static org.osm2world.test.TestUtil.assertAlmostEquals;
 import static org.osm2world.test.TestUtil.assertSameCyclicOrder;
 
@@ -18,15 +18,15 @@
 
 public class SimplePolygonXZTest {
 
-	private SimplePolygonXZ p1 = new SimplePolygonXZ(asList(
+	private final SimplePolygonXZ p1 = new SimplePolygonXZ(asList(
 			new VectorXZ(-1, -1),
 			new VectorXZ(-1,  0),
 			new VectorXZ(-1, +1),
 			new VectorXZ(+1, +1),
 			new VectorXZ(+1, -1),
 			new VectorXZ(-1, -1)));
 
-	private SimplePolygonXZ p2 = new SimplePolygonXZ(asList(
+	private final SimplePolygonXZ p2 = new SimplePolygonXZ(asList(
 			new VectorXZ(-0.5, -0.5),
 			new VectorXZ(-0.5, +1.5),
 			new VectorXZ(+1.5, +1.5),
@@ -127,7 +127,7 @@ public void testIsClockwise1() {
 
 		assertTrue(new SimplePolygonXZ(outlineA).isClockwise());
 
-		List<VectorXZ> outlineAInv = new ArrayList<VectorXZ>(outlineA);
+		List<VectorXZ> outlineAInv = new ArrayList<>(outlineA);
 		Collections.reverse(outlineAInv);
 		assertFalse(new SimplePolygonXZ(outlineAInv).isClockwise());
 
@@ -138,11 +138,33 @@ public void testIsClockwise2() {
 
 		assertTrue(new SimplePolygonXZ(outlineB).isClockwise());
 
-		List<VectorXZ> outlineBInv = new ArrayList<VectorXZ>(outlineB);
+		List<VectorXZ> outlineBInv = new ArrayList<>(outlineB);
 		Collections.reverse(outlineBInv);
 		assertFalse(new SimplePolygonXZ(outlineBInv).isClockwise());
 	}
 
+	@Test
+	public void testMakeCounterclockwise() {
+
+		for (List<VectorXZ> outline : List.of(outlineA, outlineB)) {
+
+			var poly = new SimplePolygonXZ(outline);
+			assertTrue(poly.isClockwise());
+
+			var polyCCW = poly.makeCounterclockwise();
+			assertFalse(polyCCW.isClockwise());
+			assertEquals(poly.getArea(), polyCCW.getArea(), 1e-3);
+
+			var polyInv = poly.reverse();
+			assertFalse(polyInv.isClockwise());
+			assertEquals(polyCCW, polyInv);
+
+			assertEquals(poly, polyInv.reverse());
+
+		}
+
+	}
+
 	@Test
 	public void testIsClockwise3() {
 

core/src/main/java/org/osm2world/math/shapes/SimplePolygonXZ.java

@@ -50,6 +50,22 @@ public SimplePolygonXZ(List<VectorXZ> vertexLoop) {
 
 	}
 
+	/**
+	 * Internal alternative to {@link #SimplePolygonXZ(List)} that omits validity checks
+	 * and, optionally, area calculations. This can avoid unnecessary performance costs for known-good data.
+	 */
+	private SimplePolygonXZ(List<VectorXZ> vertexLoop, Double signedArea) {
+
+		this.vertexLoop = vertexLoop;
+
+		if (signedArea != null) {
+			this.signedArea = signedArea;
+			this.area = Math.abs(signedArea);
+			this.clockwise = signedArea < 0;
+		}
+
+	}
+
 	public static final SimplePolygonXZ asSimplePolygon(SimpleClosedShapeXZ shape) {
 		if (shape instanceof SimplePolygonXZ) {
 			return (SimplePolygonXZ) shape;
@@ -310,9 +326,9 @@ private SimplePolygonXZ makeRotationSense(boolean clockwise) {
 	}
 
 	public SimplePolygonXZ reverse() {
-		List<VectorXZ> newVertexLoop = new ArrayList<VectorXZ>(vertexLoop);
+		List<VectorXZ> newVertexLoop = new ArrayList<>(vertexLoop);
 		Collections.reverse(newVertexLoop);
-		return new SimplePolygonXZ(newVertexLoop);
+		return new SimplePolygonXZ(newVertexLoop, -this.signedArea);
 	}
 
 	@Override
@@ -690,7 +706,7 @@ private static void assertNotSelfIntersecting(List<VectorXZ> vertexLoop) {
 	 */
 	private static void assertNoDuplicates(List<VectorXZ> vertexLoop) {
 		for (int i = 0; i < vertexLoop.size() - 1; i++) {
-			if (vertexLoop.get(i + 1).distanceTo(vertexLoop.get(i)) == 0) {
+			if (VectorXZ.distanceSquared(vertexLoop.get(i + 1), vertexLoop.get(i)) == 0) {
 				throw new InvalidGeometryException(
 						"polygon must not not have duplicate points\n"
 						+ "Polygon vertices: " + vertexLoop);