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Another try at fixing longitude wraparound for bins (#261)

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* Another try at fixing longitude wraparound for bins

* Gonna get it right this time

* Forgot to update the comment

* The filter case was not supposed to reinterpret geometry

* Copy antimeridian-crossing geometries to the other side too

* Getting closer to getting antimeridian-crossing polygons right

* Update changelog and version
This commit is contained in:
Erica Fischer
2024-09-10 14:25:57 -07:00
committed by GitHub
parent 51fcf142df
commit 84f6e887a7
13 changed files with 3772 additions and 17 deletions
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read_json.cpp
+57 -13
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@@ -178,7 +178,7 @@ static std::vector<mvt_geometry> to_feature(drawvec &geom) {
return out;
}
std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int extent) {
std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int extent, bool fix_longitudes) {
std::map<std::string, mvt_layer> ret;
std::shared_ptr<std::string> tile_stringpool = std::make_shared<std::string>();
@@ -278,6 +278,57 @@ std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int
drawvec dv;
parse_geometry(t, coordinates, dv, VT_MOVETO, "Filter output", jp->line, j);
// handle longitude wraparound
//
// this is supposed to be data for a single tile,
// so any jump from the left hand side edge of the world
// to the right edge, or vice versa, is unexpected,
// so move it to the other side.
if (fix_longitudes && mb_geometry[t] == VT_POLYGON) {
const long long quarter_world = 1LL << 30;
const long long world = 1LL << 32;
bool copy_to_left = false;
bool copy_to_right = false;
for (size_t i = 0; i < dv.size(); i++) {
// is this vertex on a different side of the world
// than the first vertex? then shift this one to match
if (i > 0) {
if ((dv[0].x < quarter_world) && (dv[i].x > 3 * quarter_world)) {
dv[i].x -= world;
}
if ((dv[0].x > 3 * quarter_world) && (dv[i].x < quarter_world)) {
dv[i].x += world;
}
}
// does it stick off the edge of the world?
// then we need another copy on the other side of the world
if (dv[i].x < 0) {
copy_to_right = true;
}
if (dv[i].x > world) {
copy_to_left = true;
}
}
if (copy_to_left) {
size_t n = dv.size();
for (size_t i = 0; i < n; i++) {
dv.emplace_back(dv[i].op, dv[i].x - world, (long long) dv[i].y);
}
}
if (copy_to_right) {
size_t n = dv.size();
for (size_t i = 0; i < n; i++) {
dv.emplace_back(dv[i].op, dv[i].x + world, (long long) dv[i].y);
}
}
}
if (mb_geometry[t] == VT_POLYGON) {
dv = fix_polygon(dv, false, false);
}
@@ -286,26 +337,19 @@ std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int
for (size_t i = 0; i < dv.size(); i++) {
long long scale = 1LL << (32 - z);
// offset
// offset to tile
dv[i].x -= scale * x;
dv[i].y -= scale * y;
// handle longitude wraparound
if (dv[i].x > 2 * scale && dv[i].x - (1LL << 32) > -3 * scale) {
dv[i].x -= 1LL << 32;
}
if (dv[i].x < -3 * scale && dv[i].x + (1LL << 32) < 2 * scale) {
dv[i].x += 1LL << 32;
}
// scale
// scale to tile
dv[i].x = std::round(dv[i].x * extent / (double) scale);
dv[i].y = std::round(dv[i].y * extent / (double) scale);
}
if (mb_geometry[t] == VT_POLYGON) {
// we can try scaling up because these are tile coordinates
dv = clean_or_clip_poly(dv, 0, 0, false, true);
// don't try scaling up because we may have coordinates
// on the other side of the world
dv = clean_or_clip_poly(dv, z, 256, true, false);
if (dv.size() < 3) {
dv.clear();
}