nknize commented on a change in pull request #771: LUCENE-8620: Update
Tessellator logic to label if triangle edges belongs to the original polygon
URL: https://github.com/apache/lucene-solr/pull/771#discussion_r321718423
##########
File path: lucene/sandbox/src/java/org/apache/lucene/geo/Tessellator.java
##########
@@ -590,14 +601,123 @@ private static final boolean splitEarcut(Object
polygon, final Node start, final
return false;
}
+ /** Computes if edge defined by a and b overlaps with a polygon edge **/
+ private static boolean edgeFromPolygon(final Node a, final Node b, final
boolean isMorton) {
+ if (isMorton) {
+ return mortonEdgeFromPolygon(a, b);
+ }
+ Node next = a;
+ do {
+ if (pointInLine(next, next.next, a) && pointInLine(next, next.next, b)) {
+ return next.nextEdgeFromPolygon;
+ }
+ if (pointInLine(next, next.previous, a) && pointInLine(next,
next.previous, b)) {
+ return next.previous.nextEdgeFromPolygon;
+ }
+ next = next.next;
+ } while(next != a);
+ return false;
+ }
+
+ /** Uses morton code for speed to determine whether or not and edge defined
by a and b overlaps with a polygon edge */
+ private static final boolean mortonEdgeFromPolygon(final Node a, final Node
b) {
+ // edge bbox (flip the bits so negative encoded values are < positive
encoded values)
+ final int minTX = StrictMath.min(a.x, b.x) ^ 0x80000000;
+ final int minTY = StrictMath.min(a.y, b.y) ^ 0x80000000;
+ final int maxTX = StrictMath.max(a.x, b.x) ^ 0x80000000;
+ final int maxTY = StrictMath.max(a.y, b.y) ^ 0x80000000;
+
+ // z-order range for the current edge;
+ final long minZ = BitUtil.interleave(minTX, minTY);
+ final long maxZ = BitUtil.interleave(maxTX, maxTY);
+
+ // now make sure we don't have other points inside the potential ear;
+
+ // look for points inside edge in both directions
+ Node p = a.previousZ;
+ Node n = a.nextZ;
+ while (p != null && Long.compareUnsigned(p.morton, minZ) >= 0
+ && n != null && Long.compareUnsigned(n.morton, maxZ) <= 0) {
+ if (pointInLine(p, p.next, a) && pointInLine(p, p.next, b)) {
+ return p.nextEdgeFromPolygon;
+ }
+ if (pointInLine(p, p.previous, a) && pointInLine(p, p.previous, b)) {
+ return p.previous.nextEdgeFromPolygon;
+ }
+
+ p = p.previousZ;
+
+ if (pointInLine(n, n.next, a) && pointInLine(n, n.next, b)) {
+ return n.nextEdgeFromPolygon;
+ }
+ if (pointInLine(n, n.previous, a) && pointInLine(n, n.previous, b)) {
+ return n.previous.nextEdgeFromPolygon;
+ }
+
+ n = n.nextZ;
+ }
+
+ // first look for points inside the edge in decreasing z-order
+ while (p != null && Long.compareUnsigned(p.morton, minZ) >= 0) {
+ if (pointInLine(p, p.next, a) && pointInLine(p, p.next, b)) {
+ return p.nextEdgeFromPolygon;
+ }
+ if (pointInLine(p, p.previous, a) && pointInLine(p, p.previous, b)) {
+ return p.previous.nextEdgeFromPolygon;
+ }
+ p = p.previousZ;
+ }
+ // then look for points in increasing z-order
+ while (n != null &&
+ Long.compareUnsigned(n.morton, maxZ) <= 0) {
+ if (pointInLine(n, n.next, a) && pointInLine(n, n.next, b)) {
+ return n.nextEdgeFromPolygon;
+ }
+ if (pointInLine(n, n.previous, a) && pointInLine(n, n.previous, b)) {
+ return n.previous.nextEdgeFromPolygon;
+ }
+ n = n.nextZ;
+ }
+ return false;
+ }
+
+ private static boolean pointInLine(final Node a, final Node b, final Node
point) {
Review comment:
```suggestion
private static boolean isPointInLine(final Node a, final Node b, final
Node point) {
```
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