Fix Intersector.intersectPolygons() corner case (#7278)

libgdx · Feb 19, 2024 · 7bed7d3 · 7bed7d3
1 parent 0de4d89
commit 7bed7d3
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Showing 2 changed files with 13 additions and 4 deletions.
diff --git a/gdx/src/com/badlogic/gdx/math/Intersector.java b/gdx/src/com/badlogic/gdx/math/Intersector.java
@@ -197,7 +197,8 @@ public static boolean intersectPolygons (Polygon p1, Polygon p2, Polygon overlap
 			floatArray2.addAll(floatArray);
 			floatArray.clear();
 		}
-		if (floatArray2.size != 0) {
+		// Check for 3 or more vertices needed due to floating point precision errors
+		if (floatArray2.size >= 6) {
 			if (overlap != null) {
 				if (overlap.getVertices().length == floatArray2.size)
 					System.arraycopy(floatArray2.items, 0, overlap.getVertices(), 0, floatArray2.size);

diff --git a/gdx/test/com/badlogic/gdx/math/IntersectorTest.java b/gdx/test/com/badlogic/gdx/math/IntersectorTest.java
@@ -5,9 +5,7 @@
 
 import org.junit.Test;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.*;
 
 public class IntersectorTest {
 
@@ -223,4 +221,14 @@ public void testIsPointInTriangle3D () {
 			new Vector3(50.008057f, 22.20586f, 124.62208f), new Vector3(62.282288f, 22.205864f, 109.665924f),
 			new Vector3(70.92052f, 7.205861f, 115.437805f)));
 	}
+
+	@Test
+	public void testIntersectPolygons () {
+		// Corner case with extremely small overlap polygon
+		Polygon intersectionPolygon = new Polygon();
+		assertFalse(
+			Intersector.intersectPolygons(new Polygon(new float[] {3200.1453f, 88.00839f, 3233.9087f, 190.34174f, 3266.2905f, 0.0f}),
+				new Polygon(new float[] {3213.0f, 131.0f, 3214.0f, 131.0f, 3214.0f, 130.0f, 3213.0f, 130.0f}), intersectionPolygon));
+		assertEquals(0, intersectionPolygon.getVertexCount());
+	}
 }