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Only reinspect segments that changed in the previous pass

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This commit is contained in:
Erica Fischer
2023-11-13 12:12:58 -08:00
parent d23f0a243b
commit 1238711571
1 changed files with 59 additions and 24 deletions
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polygon.cpp
+59 -24
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@@ -40,7 +40,7 @@ struct point {
typedef std::pair<point, point> segment;
bool fix_opposites(std::vector<segment> &segs) {
bool fix_opposites(std::vector<segment> &segs, std::set<segment> &affected) {
bool changed = false;
std::multimap<segment, size_t> opposites;
segment erased = std::make_pair(point(INT_MAX, INT_MAX), point(INT_MAX, INT_MAX));
@@ -73,6 +73,9 @@ bool fix_opposites(std::vector<segment> &segs) {
segs.emplace_back(point(cx, cy), segs[i].second);
segs[i] = std::make_pair(segs[i].first, point(cx, cy));
affected.insert(segs[i]);
affected.insert(segs.back());
changed = true;
// segs[i] is not erased, so segs[f.first->second]
@@ -107,6 +110,7 @@ const std::pair<double, double> SAME_SLOPE = std::make_pair(-INT_MAX, INT_MAX);
// which does not seem to produce correct results.
std::pair<double, double> get_line_intersection(long long p0_x, long long p0_y, long long p1_x, long long p1_y,
long long p2_x, long long p2_y, long long p3_x, long long p3_y) {
// bounding box reject, x
long long min01x = std::min(p0_x, p1_x);
long long max01x = std::max(p0_x, p1_x);
long long min23x = std::min(p2_x, p3_x);
@@ -115,6 +119,7 @@ std::pair<double, double> get_line_intersection(long long p0_x, long long p0_y,
return std::make_pair(-1, -1);
}
// bounding box reject, y
long long min01y = std::min(p0_y, p1_y);
long long max01y = std::max(p0_y, p1_y);
long long min23y = std::min(p2_y, p3_y);
@@ -142,18 +147,21 @@ std::pair<double, double> get_line_intersection(long long p0_x, long long p0_y,
return SAME_SLOPE;
}
bool vertical(std::vector<segment> &segs, size_t s, long long y) {
bool vertical(std::vector<segment> &segs, size_t s, long long y, std::set<segment> &affected) {
if ((y > segs[s].first.y && y < segs[s].second.y) ||
(y > segs[s].second.y && y < segs[s].first.y)) {
segs.push_back(std::make_pair(point(segs[s].first.x, y), segs[s].second));
segs[s] = std::make_pair(segs[s].first, point(segs[s].first.x, y));
affected.insert(segs[s]);
affected.insert(segs.back());
return true;
}
return false;
}
bool horizontal(std::vector<segment> &segs, size_t s, long long x) {
bool horizontal(std::vector<segment> &segs, size_t s, long long x, std::set<segment> &affected) {
if ((x > segs[s].first.x && x < segs[s].second.x) ||
(x > segs[s].second.x && x < segs[s].first.x)) {
double slope = (segs[s].second.y - segs[s].first.y) /
@@ -161,13 +169,16 @@ bool horizontal(std::vector<segment> &segs, size_t s, long long x) {
long long y = std::llround(segs[s].first.y + slope * (x - segs[s].first.x));
segs.push_back(std::make_pair(point(x, y), segs[s].second));
segs[s] = std::make_pair(segs[s].first, point(x, y));
affected.insert(segs[s]);
affected.insert(segs.back());
return true;
}
return false;
}
bool intersect_collinear(std::vector<segment> &segs, size_t s1, size_t s2) {
bool intersect_collinear(std::vector<segment> &segs, size_t s1, size_t s2, std::set<segment> &affected) {
bool changed = false;
if (segs[s1].first.x == segs[s1].second.x) {
@@ -179,16 +190,16 @@ bool intersect_collinear(std::vector<segment> &segs, size_t s1, size_t s2) {
if (segs[s1].first.x == segs[s2].first.x) {
// collinear, not parallel
if (vertical(segs, s1, segs[s2].first.y)) {
if (vertical(segs, s1, segs[s2].first.y, affected)) {
changed = true;
}
if (vertical(segs, s1, segs[s2].second.y)) {
if (vertical(segs, s1, segs[s2].second.y, affected)) {
changed = true;
}
if (vertical(segs, s2, segs[s1].first.y)) {
if (vertical(segs, s2, segs[s1].first.y, affected)) {
changed = true;
}
if (vertical(segs, s2, segs[s1].second.y)) {
if (vertical(segs, s2, segs[s1].second.y, affected)) {
changed = true;
}
}
@@ -215,16 +226,16 @@ bool intersect_collinear(std::vector<segment> &segs, size_t s1, size_t s2) {
if (y1 == y2) {
// collinear, not parallel
if (horizontal(segs, s1, segs[s2].first.x)) {
if (horizontal(segs, s1, segs[s2].first.x, affected)) {
changed = true;
}
if (horizontal(segs, s1, segs[s2].second.x)) {
if (horizontal(segs, s1, segs[s2].second.x, affected)) {
changed = true;
}
if (horizontal(segs, s2, segs[s1].first.x)) {
if (horizontal(segs, s2, segs[s1].first.x, affected)) {
changed = true;
}
if (horizontal(segs, s2, segs[s1].second.x)) {
if (horizontal(segs, s2, segs[s1].second.x, affected)) {
changed = true;
}
}
@@ -240,7 +251,7 @@ bool intersect_collinear(std::vector<segment> &segs, size_t s1, size_t s2) {
return changed;
}
bool intersect(std::vector<segment> &segs, size_t s1, size_t s2) {
bool intersect(std::vector<segment> &segs, size_t s1, size_t s2, std::set<segment> &affected) {
auto intersections = get_line_intersection(segs[s1].first.x, segs[s1].first.y,
segs[s1].second.x, segs[s1].second.y,
segs[s2].first.x, segs[s2].first.y,
@@ -258,7 +269,10 @@ bool intersect(std::vector<segment> &segs, size_t s1, size_t s2) {
// printf("introduce %f,%f in %f,%f to %f,%f (s1 %zu %zu)\n", x, y, segs[s1].first.x, segs[s1].first.y, segs[s1].second.x, segs[s1].second.y, s1, s2);
segs.push_back(std::make_pair(point(x, y), segs[s1].second));
segs[s1] = std::make_pair(segs[s1].first, point(x, y));
changed = true;
affected.insert(segs[s1]);
affected.insert(segs.back());
}
if ((x == segs[s2].first.x && y == segs[s2].first.y) ||
@@ -269,10 +283,13 @@ bool intersect(std::vector<segment> &segs, size_t s1, size_t s2) {
// printf("introduce %lld,%lld in %lld,%lld to %lld,%lld (s2)\n", std::llround(x), std::llround(y), std::llround(segs[s2].first.x), std::llround(segs[s2].first.y), std::llround(segs[s2].second.x), std::llround(segs[s2].second.y));
segs.push_back(std::make_pair(point(x, y), segs[s2].second));
segs[s2] = std::make_pair(segs[s2].first, point(x, y));
changed = true;
affected.insert(segs[s2]);
affected.insert(segs.back());
}
} else if (intersections == SAME_SLOPE) {
if (intersect_collinear(segs, s1, s2)) {
if (intersect_collinear(segs, s1, s2, affected)) {
changed = true;
}
} else {
@@ -302,8 +319,22 @@ struct scan_transition {
void snap_round(std::vector<segment> &segs) {
bool again = true;
// affected is indexed by segment instead of just segment index
// because fix_opposites() causes renumbering
std::set<segment> affected;
while (again) {
again = false;
std::set<segment> previously_affected = affected;
affected.clear();
#if 0
if (previously_affected.size() == 0) {
fprintf(stderr, "inspect %zu\n", segs.size());
} else {
fprintf(stderr, "reinspect %zu\n", previously_affected.size());
}
#endif
// find identical opposite-winding segments and adjust for them
//
@@ -311,7 +342,7 @@ void snap_round(std::vector<segment> &segs) {
// in the course of trying to keep spindles alive, and will then need to
// resolve those.
if (fix_opposites(segs)) {
if (fix_opposites(segs, affected)) {
again = true;
}
@@ -357,16 +388,20 @@ void snap_round(std::vector<segment> &segs) {
for (size_t s1 : active) {
for (size_t s2 : active) {
if (s1 < s2) {
if (already.find(std::make_pair(s1, s2)) == already.end()) {
if (intersect(segs, s1, s2)) {
// if the segments intersected,
// we need to do another scan,
// because introducing a new node
// may have caused new intersections
again = true;
}
if (previously_affected.size() == 0 || // first time
previously_affected.count(segs[s1]) > 0 ||
previously_affected.count(segs[s2]) > 0) {
if (already.find(std::make_pair(s1, s2)) == already.end()) {
if (intersect(segs, s1, s2, affected)) {
// if the segments intersected,
// we need to do another scan,
// because introducing a new node
// may have caused new intersections
again = true;
}
already.insert(std::make_pair(s1, s2));
already.insert(std::make_pair(s1, s2));
}
}
}
}