better robustness and performance with holes

README.md

@@ -23,10 +23,10 @@ Some benchmarks:
 
 (ops/sec)         | pts  | earcut    | libtess  | poly2tri | pnltri
 ------------------| ---- | --------- | -------- | -------- | ---------
-OSM building      | 15   | _605,427_ | _28,124_ | _28,131_ | _210,320_
-dude shape        | 94   | _28,757_  | _5,904_  | _3,544_  | _12,916_
-holed dude shape  | 104  | _11,575_  | _5,204_  | _3,205_  | _2,232_
-complex OSM water | 2523 | _35.93_   | _64.73_  | failure  | failure
+OSM building      | 15   | _603,533_ | _28,124_ | _28,131_ | _210,320_
+dude shape        | 94   | _28,620_  | _5,904_  | _3,544_  | _12,916_
+holed dude shape  | 104  | _13,913_  | _5,204_  | _3,205_  | _2,232_
+complex OSM water | 2523 | _45.13_   | _64.73_  | failure  | failure
 
 Earcut may be slow for huge complex shapes,
 but when it comes to triangulating lots of shapes with relatively low number of vertices on average
@@ -74,8 +74,8 @@ npm test
 
 ##### 1.1.0 (Jan 21)
 
-- Improved performance on complex polygons with lots of holes
-by switching from Held to Eberly hole elimination algorithm
+- Improved performance on polygons with holes by switching from Held to Eberly hole elimination algorithm
+- More robustness fixes and tests
 
 ##### 1.0.1 — 1.0.6 (Jan 20, 2015)
 

src/earcut.js

@@ -4,9 +4,9 @@ module.exports = earcut;
 
 function earcut(points) {
 
-    var outerNode = filterPoints(linkedList(points[0], true));
+    var outerNode = linkedList(points[0], true);
 
-    if (points.length > 1) eliminateHoles(points, outerNode);
+    if (points.length > 1) outerNode = eliminateHoles(points, outerNode);
 
     var triangles = [];
     if (outerNode) earcutLinked(outerNode, triangles);
@@ -58,7 +58,10 @@ function filterPoints(start) {
     return start;
 }
 
-function earcutLinked(ear, triangles) {
+function earcutLinked(ear, triangles, secondPass) {
+    ear = filterPoints(ear);
+    if (!ear) return;
+
     var stop = ear,
         prev, next;
 
@@ -82,8 +85,10 @@ function earcutLinked(ear, triangles) {
         ear = next;
 
         if (ear === stop) {
-            // if we can't find valid ears anymore, split remaining polygon into two
-            splitEarcut(ear, triangles);
+            // if we can't find any more ears, try filtering points and cutting again
+            if (!secondPass) earcutLinked(ear, triangles, true);
+            // if this didn't work, try splitting the remaining polygon into two
+            else splitEarcut(ear, triangles);
             break;
         }
     }
@@ -135,11 +140,6 @@ function isEar(ear) {
 
 function splitEarcut(start, triangles) {
     // find a valid diagonal that divides the polygon into two
-
-    start = filterPoints(start);
-    if (!start) return;
-
-    // iterate through all potential diagonals
     var a = start;
     do {
         var b = a.next.next;
@@ -170,7 +170,12 @@ function eliminateHoles(points, outerNode) {
     queue.sort(compareX);
 
     // process holes from left to right
-    for (i = 0; i < queue.length; i++) eliminateHole(queue[i], outerNode);
+    for (i = 0; i < queue.length; i++) {
+        eliminateHole(queue[i], outerNode);
+        outerNode = filterPoints(outerNode);
+    }
+
+    return outerNode;
 }
 
 function eliminateHole(holeNode, outerNode) {

test/fixtures/empty-square.json

@@ -0,0 +1,4 @@
+[
+[[0,0],[4000,0],[4000,4000],[0,4000]],
+[[0,0],[4000,0],[4000,4000],[0,4000]]
+]

test/fixtures/water3b.json

@@ -0,0 +1,5 @@
+[
+[[-128,4224],[-128,-128],[4224,-128],[4224,4224],[-128,4224]],
+[[3832,-21],[3840,-17],[3877,21],[3895,39],[3961,-21],[3893,-98],[3855,-128],[3688,-128],[3742,-81],[3793,-41],[3832,-21],[3832,-21]],
+[[4205,596],[4224,572],[4224,248],[4166,163],[4119,50],[4020,36],[4004,21],[3969,21],[3936,62],[3982,117],[4088,293],[4152,419],[4185,544],[4205,596],[4205,596]]
+]

test/test.js

@@ -7,11 +7,13 @@ areaTest('dude');
 areaTest('water', 0.0021);
 areaTest('water2');
 areaTest('water3');
+areaTest('water3b');
 areaTest('water4');
-areaTest('water-huge', 0.0012);
+areaTest('water-huge', 0.0021);
 areaTest('water-huge2', 0.0023);
 areaTest('degenerate');
 areaTest('bad-hole', 0.05);
+areaTest('empty-square');
 
 function areaTest(filename, expectedDeviation) {
     expectedDeviation = expectedDeviation || 0.000001;