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Prevent date line wrap around due to creating an expanded polygon from a

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line that might touch the dateline.
This commit is contained in:
curt 2005-12-19 15:54:58 +00:00
parent 99f280eb08
commit e444f54d6d
1 changed files with 61 additions and 6 deletions
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67
src/Lib/Geometry/util.cxx
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@ -15,18 +15,24 @@
namespace tg {
/*
* Computer the intersection point of two lines. Reference:
* http://astronomy.swin.edu.au/~pbourke/geometry/lineline2d/
*/
bool
getIntersection (const Point3D &p0, const Point3D &p1,
const Point3D &p2, const Point3D &p3,
Point3D &intersection)
{
const double my_eps = 0.00000000000001;
double u_num =
((p3.x()-p2.x())*(p0.y()-p2.y()))-((p3.y()-p2.y())*(p0.x()-p2.x()));
double u_den =
((p3.y()-p2.y())*(p1.x()-p0.x()))-((p3.x()-p2.x())*(p1.y()-p0.y()));
if (u_den == 0) {
if (u_num == 0) {
if ( fabs(u_den) < my_eps ) {
if ( fabs(u_num) < my_eps ) {
SG_LOG(SG_GENERAL, SG_ALERT, "Intersection: coincident lines");
} else {
SG_LOG(SG_GENERAL, SG_ALERT, "Intersection: parallel lines");
@ -34,6 +40,7 @@ getIntersection (const Point3D &p0, const Point3D &p1,
return false;
} else {
double u = u_num/u_den;
// cout << "u = " << u << " u_num = " << u_num << " u_den = " << u_den << endl;
intersection = Point3D((p0.x()+u*(p1.x()-p0.x())),
(p0.y()+u*(p1.y()-p0.y())),
0);
@ -92,20 +99,57 @@ makePolygon (const Line &line, int width, TGPolygon &polygon)
// Wind each rectangle counterclockwise
// Corner 1
// cout << "point = " << i << endl;
geo_direct_wgs_84(0, p1.y(), p1.x(), CLAMP_ANGLE(angle1+90), width/2, &y, &x, &az);
// Sometimes creating the new point can wrap the date line, even if the
// original line does not. This can cause problems later, so lets just
// clip the result to date line and hope that the typical error is very
// small. FIXME: we should handle this more robustly in case larger
// structures cross the date line, but that implies a much broader swath
// of changes.
if ( x - p1.x() > 180.0 ) x = -180.0;
else if ( x - p1.x() < -180.0 ) x = 180.0;
polygon.add_node(0, Point3D(x, y, 0));
// cout << "corner 1 = " << Point3D(x, y, 0) << endl;
// Corner 2
geo_direct_wgs_84(0, p2.y(), p2.x(), CLAMP_ANGLE(angle1+90), width/2, &y, &x, &az);
// Sometimes creating the new point can wrap the date line, even if the
// original line does not. This can cause problems later, so lets just
// clip the result to date line and hope that the typical error is very
// small. FIXME: we should handle this more robustly in case larger
// structures cross the date line, but that implies a much broader swath
// of changes.
if ( x - p2.x() > 180.0 ) x = -180.0;
else if ( x - p2.x() < -180.0 ) x = 180.0;
polygon.add_node(0, Point3D(x, y, 0));
// cout << "corner 2 = " << Point3D(x, y, 0) << endl;
// Corner 3
geo_direct_wgs_84(0, p2.y(), p2.x(), CLAMP_ANGLE(angle1-90), width/2, &y, &x, &az);
// Sometimes creating the new point can wrap the date line, even if the
// original line does not. This can cause problems later, so lets just
// clip the result to date line and hope that the typical error is very
// small. FIXME: we should handle this more robustly in case larger
// structures cross the date line, but that implies a much broader swath
// of changes.
if ( x - p2.x() > 180.0 ) x = -180.0;
else if ( x - p2.x() < -180.0 ) x = 180.0;
polygon.add_node(0, Point3D(x, y, 0));
// cout << "corner 3 = " << Point3D(x, y, 0) << endl;
// Corner 4
geo_direct_wgs_84(0, p1.y(), p1.x(), CLAMP_ANGLE(angle1-90), width/2, &y, &x, &az);
// Sometimes creating the new point can wrap the date line, even if the
// original line does not. This can cause problems later, so lets just
// clip the result to date line and hope that the typical error is very
// small. FIXME: we should handle this more robustly in case larger
// structures cross the date line, but that implies a much broader swath
// of changes.
if ( x - p1.x() > 180.0 ) x = -180.0;
else if ( x - p1.x() < -180.0 ) x = 180.0;
polygon.add_node(0, Point3D(x, y, 0));
// cout << "corner 4 = " << Point3D(x, y, 0) << endl;
// Save this rectangle
segment_list.push_back(polygon);
@ -120,31 +164,42 @@ makePolygon (const Line &line, int width, TGPolygon &polygon)
int nSegments = segment_list.size();
Point3D intersection;
polygon.add_node(0, segment_list[0].get_pt(0, 0));
// cout << "bnode = " << segment_list[0].get_pt(0, 0) << endl;
for (i = 0; i < nSegments - 1; i++) {
// cout << "point = " << i << endl;
if (getIntersection(segment_list[i].get_pt(0, 0),
segment_list[i].get_pt(0, 1),
segment_list[i+1].get_pt(0, 0),
segment_list[i+1].get_pt(0, 1),
intersection))
intersection)) {
polygon.add_node(0, intersection);
else
// cout << "bnode (int) = " << intersection << endl;
} else {
polygon.add_node(0, segment_list[i].get_pt(0, 1));
// cout << "bnode = " << segment_list[i].get_pt(0, 1) << endl;
}
}
polygon.add_node(0, segment_list[nSegments-1].get_pt(0, 1));
// cout << "bnode = " << segment_list[nSegments-1].get_pt(0, 1) << endl;
// Connect the top part
polygon.add_node(0, segment_list[nSegments-1].get_pt(0, 2));
// cout << "tnode = " << segment_list[nSegments-1].get_pt(0, 2) << endl;
for (i = nSegments - 1; i > 0; i--) {
if (getIntersection(segment_list[i].get_pt(0, 2),
segment_list[i].get_pt(0, 3),
segment_list[i-1].get_pt(0, 2),
segment_list[i-1].get_pt(0, 3),
intersection))
intersection)) {
polygon.add_node(0, intersection);
else
// cout << "tnode (int) = " << intersection << endl;
} else {
polygon.add_node(0, segment_list[i].get_pt(0, 3));
// cout << "tnode = " << segment_list[i].get_pt(0, 3) << endl;
}
}
polygon.add_node(0, segment_list[0].get_pt(0, 3));
// cout << "tnode = " << segment_list[0].get_pt(0, 3) << endl;
}