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Rewritten the medial axis algorithm, now more robust (don't just prune MAT from endpoints, but validate all single edges)

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This commit is contained in:
Alessandro Ranellucci 2016-03-20 20:20:32 +01:00
parent e4147a6bed
commit 7041bb5bd9
7 changed files with 231 additions and 209 deletions
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50
xs/src/libslic3r/ExPolygon.cpp
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@ -7,6 +7,7 @@
#include "polypartition.h"
#include "poly2tri/poly2tri.h"
#include <algorithm>
#include <cassert>
#include <list>
namespace Slic3r {
@ -194,6 +195,7 @@ ExPolygon::medial_axis(double max_width, double min_width, ThickPolylines* polyl
svg.Close();
*/
bool removed = false;
for (size_t i = 0; i < pp.size(); ++i) {
ThickPolyline& polyline = pp[i];
@ -203,7 +205,7 @@ ExPolygon::medial_axis(double max_width, double min_width, ThickPolylines* polyl
call, so we keep the inner point until we perform the second intersection() as well */
Point new_front = polyline.points.front();
Point new_back = polyline.points.back();
if (polyline.endpoints.front() && !this->has_boundary_point(new_front)) {
if (polyline.endpoints.first && !this->has_boundary_point(new_front)) {
Line line(polyline.points.front(), polyline.points[1]);
// prevent the line from touching on the other side, otherwise intersection() might return that solution
@ -212,7 +214,7 @@ ExPolygon::medial_axis(double max_width, double min_width, ThickPolylines* polyl
line.extend_start(max_width);
(void)this->contour.intersection(line, &new_front);
}
if (polyline.endpoints.back() && !this->has_boundary_point(new_back)) {
if (polyline.endpoints.second && !this->has_boundary_point(new_back)) {
Line line(
*(polyline.points.end() - 2),
polyline.points.back()
@ -230,14 +232,54 @@ ExPolygon::medial_axis(double max_width, double min_width, ThickPolylines* polyl
/* remove too short polylines
(we can't do this check before endpoints extension and clipping because we don't
know how long will the endpoints be extended since it depends on polygon thickness
which is variable - extension will be <= max_width/2 on each side) */
if (polyline.length() < max_width) {
which is variable - extension will be <= max_width/2 on each side)
Maybe instead of using max_width we should use max_element(polyline.width) */
if ((polyline.endpoints.first || polyline.endpoints.second)
&& polyline.length() < max_width*2) {
pp.erase(pp.begin() + i);
--i;
removed = true;
continue;
}
}
/* If we removed any short polylines we now try to connect consecutive polylines
in order to allow loop detection. Note that this algorithm is greedier than
MedialAxis::process_edge_neighbors() as it will connect random pairs of
polylines even when more than two start from the same point. This has no
drawbacks since we optimize later using nearest-neighbor which would do the
same, but should we use a more sophisticated optimization algorithm we should
not connect polylines when more than two meet. */
if (removed) {
for (size_t i = 0; i < pp.size(); ++i) {
ThickPolyline& polyline = pp[i];
if (polyline.endpoints.first && polyline.endpoints.second) continue; // optimization
// find another polyline starting here
for (size_t j = i+1; j < pp.size(); ++j) {
ThickPolyline& other = pp[j];
if (polyline.last_point().coincides_with(other.last_point())) {
other.reverse();
} else if (polyline.first_point().coincides_with(other.last_point())) {
polyline.reverse();
other.reverse();
} else if (polyline.first_point().coincides_with(other.first_point())) {
polyline.reverse();
} else if (!polyline.last_point().coincides_with(other.first_point())) {
continue;
}
polyline.points.insert(polyline.points.end(), other.points.begin() + 1, other.points.end());
polyline.width.insert(polyline.width.end(), other.width.begin(), other.width.end());
polyline.endpoints.second = other.endpoints.second;
assert(polyline.width.size() == polyline.points.size()*2 - 2);
pp.erase(pp.begin() + j);
j = i; // restart search from i+1
}
}
}
polylines->insert(polylines->end(), pp.begin(), pp.end());
}