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Precalculate which child tiles a feature can overlap

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instead of looping over them all
This commit is contained in:
Eric Fischer 2015-07-01 15:06:12 -07:00
parent 18cdcb0732
commit 1b72804358
1 changed files with 27 additions and 22 deletions
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49
tile.cc
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@ -363,8 +363,32 @@ void rewrite(drawvec &geom, int z, int nextzoom, int file_maxzoom, long long *bb
int xo, yo;
int span = 1 << (nextzoom - z);
for (xo = 0; xo < span; xo++) {
for (yo = 0; yo < span; yo++) {
// Get the feature bounding box in pixel (256) coordinates at the child zoom
// in order to calculate which sub-tiles it can touch including the buffer.
long long bbox2[4];
int k;
for (k = 0; k < 4; k++) {
// Division instead of right-shift because coordinates can be negative
bbox2[k] = bbox[k] / (1 << (32 - nextzoom - 8));
}
bbox2[0] -= buffer;
bbox2[1] -= buffer;
bbox2[2] += buffer;
bbox2[3] += buffer;
for (k = 0; k < 4; k++) {
if (bbox2[k] < 0) {
bbox2[k] = 0;
}
if (bbox2[k] >= 256 * span) {
bbox2[k] = 256 * (span - 1);
}
bbox2[k] /= 256;
}
for (xo = bbox2[0]; xo <= bbox2[2]; xo++) {
for (yo = bbox2[1]; yo <= bbox2[3]; yo++) {
unsigned jx = tx * span + xo;
unsigned jy = ty * span + yo;
@ -383,26 +407,7 @@ void rewrite(drawvec &geom, int z, int nextzoom, int file_maxzoom, long long *bb
int j = ((jx & ((1 << MAX_ZOOM_INCREMENT) - 1)) << MAX_ZOOM_INCREMENT) |
((jy & ((1 << MAX_ZOOM_INCREMENT) - 1)));
long long bbox2[4];
int k;
for (k = 0; k < 4; k++) {
bbox2[k] = bbox[k];
}
if (z != 0) {
// Offset back to world-relative
bbox2[0] += tx << (32 - z);
bbox2[1] += ty << (32 - z);
bbox2[2] += tx << (32 - z);
bbox2[3] += ty << (32 - z);
}
// Offset to child tile-relative
bbox2[0] -= (tx * span + xo) << (32 - nextzoom);
bbox2[1] -= (ty * span + yo) << (32 - nextzoom);
bbox2[2] -= (tx * span + xo) << (32 - nextzoom);
bbox2[3] -= (ty * span + yo) << (32 - nextzoom);
int quick2 = quick_check(bbox2, nextzoom, line_detail, buffer);
if (quick2 != 0) {
{
if (!within[j]) {
serialize_int(geomfile[j], nextzoom, &geompos[j], fname);
serialize_uint(geomfile[j], tx * span + xo, &geompos[j], fname);