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Tests with a description of the updated method.

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The old `containsPoint` method was sensitive to failure when looking for ray crossings with nearly vertical edges.  These added tests demonstrate the simple cases where `containsPoint` succeeds.  The tests also now include a case that covers the failure for polygons with nearly vertical edges.  The previous `getX` method (within the `containsPoint` method) and the new one are mathematically equivalent.  The updated version performs better in cases using coordinates with many significant figures.
This commit is contained in:
tschaub
2012-01-16 16:59:54 -07:00
parent 7a0336a9ef
commit 02aa9bcc36
2 changed files with 98 additions and 10 deletions
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2
lib/OpenLayers/Geometry/LinearRing.js
View File

@@ -294,7 +294,7 @@ OpenLayers.Geometry.LinearRing = OpenLayers.Class(
var px = approx(point.x, digs);
var py = approx(point.y, digs);
function getX(y, x1, y1, x2, y2) {
return (y-y2)*((x2-x1)/(y2-y1)) + x2;
return (y - y2) * ((x2 - x1) / (y2 - y1)) + x2;
}
var numSeg = this.components.length - 1;
var start, end, x1, y1, x2, y2, cx, cy;

106
tests/Geometry/LinearRing.html
View File

@@ -250,21 +250,109 @@
"resize correctly adjusts y of component 4");
}
function test_LinearRing_containsPoint(t) {
t.plan(1);
function test_containsPoint(t) {
/**
* The ring:
* edge 3
* (5, 10) __________ (15, 10)
* / /
* edge 4 / / edge 2
* / /
* (0, 0) /_________/ (10, 0)
* edge 1
*/
var components = [
new OpenLayers.Geometry.Point(-10812863.417266,3923827.912779),
new OpenLayers.Geometry.Point(-10812863.417264,3923951.5257855),
new OpenLayers.Geometry.Point(-10812309.24881,3923990.9386282),
new OpenLayers.Geometry.Point(-10812751.15038,3923798.0545649)
new OpenLayers.Geometry.Point(0, 0),
new OpenLayers.Geometry.Point(10, 0),
new OpenLayers.Geometry.Point(15, 10),
new OpenLayers.Geometry.Point(5, 10)
];
var ring = new OpenLayers.Geometry.LinearRing(components);
var point = new OpenLayers.Geometry.Point(-10812964.078829, 3923856.9524225);
function p(x, y) {
return new OpenLayers.Geometry.Point(x, y);
}
// contains: 1 (touches), true (within), false (outside)
var cases = [{
point: p(5, 5), contains: true
}, {
point: p(20, 20), contains: false
}, {
point: p(15, 15), contains: false
}, {
point: p(0, 0), contains: 1 // lower left corner
}, {
point: p(10, 0), contains: 1 // lower right corner
}, {
point: p(15, 10), contains: 1 // upper right corner
}, {
point: p(5, 10), contains: 1 // upper left corner
}, {
point: p(5, 0), contains: 1 // on edge 1
}, {
point: p(5, -0.1), contains: false // below edge 1
}, {
point: p(5, 0.1), contains: true // above edge 1
}, {
point: p(12.5, 5), contains: 1 // on edge 2
}, {
point: p(12.4, 5), contains: true // left of edge 2
}, {
point: p(12.6, 5), contains: false // right of edge 2
}, {
point: p(10, 10), contains: 1 // on edge 3
}, {
point: p(10, 9.9), contains: true // below edge 3
}, {
point: p(10, 10.1), contains: false // above edge 3
}, {
point: p(2.5, 5), contains: 1 // on edge 4
}, {
point: p(2.4, 5), contains: false // left of edge 4
}, {
point: p(2.6, 5), contains: true // right of edge 4
}];
var len = cases.length;
t.plan(len);
var c;
for (var i=0; i<len; ++i) {
c = cases[i];
t.eq(ring.containsPoint(c.point), c.contains, "case " + i + ": " + c.point);
}
}
function test_containsPoint_precision(t) {
/**
* The test for linear ring containment was sensitive to failure when
* looking for ray crossings on nearly vertical edges. With a loss
* of precision in calculating the x-coordinate for the crossing,
* the method would erronously determine that the x-coordinate was
* not within the (very narrow) x-range of the nearly vertical edge.
*
* The test below creates a polygon whose first vertical edge is
* nearly horizontal. The test point lies "far" outside the polygon
* and we expect the containsPoint method to return false.
*/
t.plan(1);
var components = [
new OpenLayers.Geometry.Point(10000020.000001, 1000000),
new OpenLayers.Geometry.Point(10000020.000002, 1000010), // nearly vertical
new OpenLayers.Geometry.Point(10000030, 1000010),
new OpenLayers.Geometry.Point(10000030, 1000000)
];
var ring = new OpenLayers.Geometry.LinearRing(components);
var point = new OpenLayers.Geometry.Point(10000000, 1000001);
t.eq(ring.containsPoint(point), false, "false for point outside polygon with nearly vertical edge");
t.ok(!ring.containsPoint(point),
"containsPoint correctly returns false for point outside");
}
</script>