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Looks terrible, but drop pieces of lines to maintain density across zooms

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This commit is contained in:
Eric Fischer 2014-09-24 14:58:26 -07:00
parent 5cde832ec6
commit e65eb0b310
1 changed files with 38 additions and 1 deletions
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39
tile.cc
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@ -197,6 +197,39 @@ int remove_noop(struct draw *geom, int n) {
return out;
}
int shrink_lines(struct draw *geom, int len, int z, int basezoom) {
double scale = 1.0 / exp(log(sqrt(2.5)) * (basezoom - z));
struct draw tmp[3 * len];
int out = 0;
int i;
for (i = 0; i < len; i++) {
if (i > 0 && (geom[i - 1].op == VT_MOVETO || geom[i - 1].op == VT_LINETO) && geom[i].op == VT_LINETO) {
long long cx = (geom[i].x + geom[i - 1].x) / 2;
long long cy = (geom[i].y + geom[i - 1].y) / 2;
tmp[out + 0].op = VT_MOVETO;
tmp[out + 0].x = cx + (geom[i - 1].x - cx) * scale;
tmp[out + 0].y = cy + (geom[i - 1].y - cy) * scale;
tmp[out + 1].op = VT_LINETO;
tmp[out + 1].x = cx + (geom[i].x - cx) * scale;
tmp[out + 1].y = cy + (geom[i].y - cy) * scale;
tmp[out + 2].op = VT_MOVETO;
tmp[out + 2].x = geom[i].x;
tmp[out + 2].y = geom[i].y;
out += 3;
} else {
tmp[out++] = geom[i];
}
}
memcpy(geom, tmp, out * sizeof(struct draw));
return out;
}
void to_tile_scale(struct draw *geom, int n, int z, int detail) {
int i;
@ -261,12 +294,16 @@ long long write_tile(struct index *start, struct index *end, char *metabase, uns
}
int len = decode_feature(&meta, NULL, z, tx, ty, detail);
struct draw geom[len];
struct draw geom[3 * len];
meta = metabase + i->fpos;
deserialize_int(&meta, &t);
decode_feature(&meta, geom, z, tx, ty, detail);
if (t == VT_LINE && z != basezoom) {
len = shrink_lines(geom, len, z, basezoom);
}
to_tile_scale(geom, len, z, detail);
if (t == VT_LINE || t == VT_POLYGON) {