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Another try at fixing longitude wraparound for bins

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This commit is contained in:
Erica Fischer
2024-09-06 11:09:34 -07:00
parent 51fcf142df
commit 8232993342
1 changed files with 29 additions and 10 deletions
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read_json.cpp
+29 -10
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@@ -282,23 +282,42 @@ std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int
dv = fix_polygon(dv, false, false); dv = fix_polygon(dv, false, false);
} }
if (z > 0) {
// handle longitude wraparound
//
// this is supposed to be data for a single tile,
// so any jump from the left hand side of the world
// to the right side, or vice versa, is unexpected,
// so move it to the other side.
//
// (unless this is z0, in which case it is still
// reasonable to have a big, world-spanning polygon,
// and I'm not sure what to do about that.)
for (size_t i = 0; i < dv.size(); i++) {
if (i > 0) {
if ((dv[0].x < (1LL << 31)) &&
(dv[i].x > (1LL << 31))) {
dv[i].x -= 1LL << 32;
}
if ((dv[0].x > (1LL << 31)) &&
(dv[i].x < (1LL << 31))) {
dv[i].x += 1LL << 32;
}
}
}
}
// Offset and scale geometry from global to tile // Offset and scale geometry from global to tile
for (size_t i = 0; i < dv.size(); i++) { for (size_t i = 0; i < dv.size(); i++) {
long long scale = 1LL << (32 - z); long long scale = 1LL << (32 - z);
// offset // offset to tile
dv[i].x -= scale * x; dv[i].x -= scale * x;
dv[i].y -= scale * y; dv[i].y -= scale * y;
// handle longitude wraparound // scale to tile
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
dv[i].x = std::round(dv[i].x * extent / (double) scale); dv[i].x = std::round(dv[i].x * extent / (double) scale);
dv[i].y = std::round(dv[i].y * extent / (double) scale); dv[i].y = std::round(dv[i].y * extent / (double) scale);
} }