add geometry.intersects method for all geometry types (closes #1072)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5458 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
2007-12-17 06:05:35 +00:00
parent 189b12d020
commit 5667311cba
9 changed files with 1135 additions and 1 deletions
@@ -41,6 +41,116 @@ OpenLayers.Geometry.LineString = OpenLayers.Class(OpenLayers.Geometry.Curve, {
                                                                  arguments);
        }
    },
+    
+    /**
+     * APIMethod: intersects
+     * Test for instersection between two geometries.  This is a cheapo
+     *     implementation of the Bently-Ottmann algorigithm.  It doesn't
+     *     really keep track of a sweep line data structure.  It is closer
+     *     to the brute force method, except that segments are sorted and
+     *     potential intersections are only calculated when bounding boxes
+     *     intersect.
+     *
+     * Parameters:
+     * geometry - {<OpenLayers.Geometry>}
+     *
+     * Returns:
+     * {Boolean} The input geometry intersects this geometry.
+     */
+    intersects: function(geometry) {
+        var intersect = false;
+        var type = geometry.CLASS_NAME;
+        if(type == "OpenLayers.Geometry.LineString" ||
+           type == "OpenLayers.Geometry.LinearRing" ||
+           type == "OpenLayers.Geometry.Point") {
+            var segs1 = this.getSortedSegments();
+            var segs2;
+            if(type == "OpenLayers.Geometry.Point") {
+                segs2 = [{
+                    x1: geometry.x, y1: geometry.y,
+                    x2: geometry.x, y2: geometry.y
+                }];
+            } else {
+                segs2 = geometry.getSortedSegments();
+            }
+            var seg1, seg1x1, seg1x2, seg1y1, seg1y2,
+                seg2, seg2y1, seg2y2;
+            // sweep right
+            outer: for(var i=0; i<segs1.length; ++i) {
+                seg1 = segs1[i];
+                seg1x1 = seg1.x1;
+                seg1x2 = seg1.x2;
+                seg1y1 = seg1.y1;
+                seg1y2 = seg1.y2;
+                inner: for(var j=0; j<segs2.length; ++j) {
+                    seg2 = segs2[j];
+                    if(seg2.x1 > seg1x2) {
+                        // seg1 still left of seg2
+                        break;
+                    }
+                    if(seg2.x2 < seg1x1) {
+                        // seg2 still left of seg1
+                        continue;
+                    }
+                    seg2y1 = seg2.y1;
+                    seg2y2 = seg2.y2;
+                    if(Math.min(seg2y1, seg2y2) > Math.max(seg1y1, seg1y2)) {
+                        // seg2 above seg1
+                        continue;
+                    }
+                    if(Math.max(seg2y1, seg2y2) < Math.min(seg1y1, seg1y2)) {
+                        // seg2 below seg1
+                        continue;
+                    }
+                    if(OpenLayers.Geometry.segmentsIntersect(seg1, seg2)) {
+                        intersect = true;
+                        break outer;
+                    }
+                }
+            }
+        } else {
+            intersect = geometry.intersects(this);
+        }
+        return intersect;
+    },
+    
+    /**
+     * Method: getSortedSegments
+     *
+     * Returns:
+     * {Array} An array of segment objects.  Segment objects have properties
+     *     x1, y1, x2, and y2.  The start point is represented by x1 and y1.
+     *     The end point is represented by x2 and y2.  Start and end are
+     *     ordered so that x1 < x2.
+     */
+    getSortedSegments: function() {
+        var numSeg = this.components.length - 1;
+        var segments = new Array(numSeg);
+        for(var i=0; i<numSeg; ++i) {
+            point1 = this.components[i];
+            point2 = this.components[i + 1];
+            if(point1.x < point2.x) {
+                segments[i] = {
+                    x1: point1.x,
+                    y1: point1.y,
+                    x2: point2.x,
+                    y2: point2.y
+                }
+            } else {
+                segments[i] = {
+                    x1: point2.x,
+                    y1: point2.y,
+                    x2: point1.x,
+                    y2: point1.y
+                }
+            }
+        }
+        // more efficient to define this somewhere static
+        function byX1(seg1, seg2) {
+            return seg1.x1 - seg2.x1;
+        }
+        return segments.sort(byX1);
+    },

    CLASS_NAME: "OpenLayers.Geometry.LineString"
 });