From d5689be4e7419cf498e628d8be0990497c261536 Mon Sep 17 00:00:00 2001
From: curt <curt>
Date: Wed, 19 May 2004 18:47:00 +0000
Subject: [PATCH] Fix an "unfortunate" bug in the binary polygon partitioning
 scheme that caused missing output (and thus missing scenery features.)  This
 could also lead to cracks in the scenery because of the nature of the
 underlying edge matching system.

---
 src/Lib/Polygon/chop-bin.cxx | 90 +++++++++++++++++++++++++++++++++---
 1 file changed, 83 insertions(+), 7 deletions(-)

diff --git a/src/Lib/Polygon/chop-bin.cxx b/src/Lib/Polygon/chop-bin.cxx
index 546337ba..9b8de83c 100644
--- a/src/Lib/Polygon/chop-bin.cxx
+++ b/src/Lib/Polygon/chop-bin.cxx
@@ -150,7 +150,7 @@ static void clip_and_write_poly( string root, long int p_index, AreaType area,
 // process polygon shape (chop up along tile boundaries and write each
 // polygon piece to a file)
 void tgChopNormalPolygon( const string& path, AreaType area,
-                       const TGPolygon& shape, bool preserve3d )
+                          const TGPolygon& shape, bool preserve3d )
 {
     Point3D min, max, p;
     // point2d min, max;
@@ -208,13 +208,89 @@ void tgChopNormalPolygon( const string& path, AreaType area,
     if ( (dx > 2880) || (dy > 1440) )
         throw sg_exception("something is really wrong in split_polygon()!!!!");
 
-    // write each out polygon for each bucket
-    for ( j = 0; j <= dy; ++j ) {
-        for ( i = 0; i <= dx; ++i ) {
-            b_cur = sgBucketOffset(min.x(), min.y(), i, j);
-            clip_and_write_poly( path, index, area, b_cur, shape,
-                                 preserve3d );
+    if ( dy <= 1 ) {
+	// we are down to at most two rows, write each column and then bail
+        for ( j = 0; j <= dy; ++j ) {
+            for ( i = 0; i <= dx; ++i ) {
+                b_cur = sgBucketOffset(min.x(), min.y(), i, j);
+                clip_and_write_poly( path, index, area, b_cur, shape,
+                                     preserve3d );
+            }
         }
+	return;
+    }
+
+    // we have two or more rows left, split in half (along a
+    // horizontal dividing line) and recurse with each half
+
+    // find mid point (integer math)
+    int mid = (dy + 1) / 2 - 1;
+
+    // determine horizontal clip line
+    SGBucket b_clip = sgBucketOffset(min.x(), min.y(), 0, mid);
+    double clip_line = b_clip.get_center_lat();
+    if ( (clip_line >= -89.0) && (clip_line < 89.0) ) {
+	clip_line += SG_HALF_BUCKET_SPAN;
+    } else if ( clip_line < -89.0 ) {
+	clip_line = -89.0;
+    } else if ( clip_line >= 89.0 ) {
+	clip_line = 90.0;
+    } else {
+	SG_LOG ( SG_GENERAL, SG_ALERT, 
+		 "Out of range latitude in clip_and_write_poly() = " 
+		 << clip_line );
+    }
+
+    {
+	//
+	// Crop bottom area (hopefully by putting this in it's own
+	// scope we can shorten the life of some really large data
+	// structures to reduce memory use)
+	//
+
+	SG_LOG ( SG_GENERAL, SG_DEBUG, 
+		 "Generating bottom half (" << min.y() << "-" <<
+		 clip_line << ")" );
+
+	TGPolygon bottom, bottom_clip;
+
+        bottom.erase();
+        bottom_clip.erase();
+
+        bottom.add_node( 0, Point3D(-180.0, min.y(), 0) );
+        bottom.add_node( 0, Point3D(180.0, min.y(), 0) );
+        bottom.add_node( 0, Point3D(180.0, clip_line, 0) );
+        bottom.add_node( 0, Point3D(-180.0, clip_line, 0) );
+
+        bottom_clip = tgPolygonInt( bottom, shape );
+
+	tgChopNormalPolygon( path, area, bottom_clip, preserve3d );
+    }
+
+    {
+	//
+	// Crop top area (hopefully by putting this in it's own scope
+	// we can shorten the life of some really large data
+	// structures to reduce memory use)
+	//
+
+	SG_LOG ( SG_GENERAL, SG_DEBUG, 
+		 "Generating top half (" << clip_line << "-" <<
+		 max.y() << ")" );
+
+	TGPolygon top, top_clip;
+
+        top.erase();
+        top_clip.erase();
+
+        top.add_node( 0, Point3D(-180.0, clip_line, 0) );
+        top.add_node( 0, Point3D(180.0, clip_line, 0) );
+        top.add_node( 0, Point3D(180.0, max.y(), 0) );
+        top.add_node( 0, Point3D(-180.0, max.y(), 0) );
+
+        top_clip = tgPolygonInt( top, shape );
+
+	tgChopNormalPolygon( path, area, top_clip, preserve3d );
     }
 }