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OrcaSlicer/src/libslic3r/ClipperUtils.cpp
bubnikv dfbae648bf Follow up on 6deb6a776d: 
Fixed orientation of contours after Elephant Foot Compensation.
2020-02-19 12:58:03 +01:00

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#include "ClipperUtils.hpp"
#include "Geometry.hpp"
#include "ShortestPath.hpp"
// #define CLIPPER_UTILS_DEBUG
#ifdef CLIPPER_UTILS_DEBUG
#include "SVG.hpp"
#endif /* CLIPPER_UTILS_DEBUG */
#include <Shiny/Shiny.h>
#define CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR (0.005f)
namespace Slic3r {
#ifdef CLIPPER_UTILS_DEBUG
bool clipper_export_enabled = false;
// For debugging the Clipper library, for providing bug reports to the Clipper author.
bool export_clipper_input_polygons_bin(const char *path, const ClipperLib::Paths &input_subject, const ClipperLib::Paths &input_clip)
{
FILE *pfile = fopen(path, "wb");
if (pfile == NULL)
return false;
uint32_t sz = uint32_t(input_subject.size());
fwrite(&sz, 1, sizeof(sz), pfile);
for (size_t i = 0; i < input_subject.size(); ++i) {
const ClipperLib::Path &path = input_subject[i];
sz = uint32_t(path.size());
::fwrite(&sz, 1, sizeof(sz), pfile);
::fwrite(path.data(), sizeof(ClipperLib::IntPoint), sz, pfile);
}
sz = uint32_t(input_clip.size());
::fwrite(&sz, 1, sizeof(sz), pfile);
for (size_t i = 0; i < input_clip.size(); ++i) {
const ClipperLib::Path &path = input_clip[i];
sz = uint32_t(path.size());
::fwrite(&sz, 1, sizeof(sz), pfile);
::fwrite(path.data(), sizeof(ClipperLib::IntPoint), sz, pfile);
}
::fclose(pfile);
return true;
err:
::fclose(pfile);
return false;
}
#endif /* CLIPPER_UTILS_DEBUG */
void scaleClipperPolygon(ClipperLib::Path &polygon)
{
PROFILE_FUNC();
for (ClipperLib::Path::iterator pit = polygon.begin(); pit != polygon.end(); ++pit) {
pit->X <<= CLIPPER_OFFSET_POWER_OF_2;
pit->Y <<= CLIPPER_OFFSET_POWER_OF_2;
}
}
void scaleClipperPolygons(ClipperLib::Paths &polygons)
{
PROFILE_FUNC();
for (ClipperLib::Paths::iterator it = polygons.begin(); it != polygons.end(); ++it)
for (ClipperLib::Path::iterator pit = (*it).begin(); pit != (*it).end(); ++pit) {
pit->X <<= CLIPPER_OFFSET_POWER_OF_2;
pit->Y <<= CLIPPER_OFFSET_POWER_OF_2;
}
}
void unscaleClipperPolygon(ClipperLib::Path &polygon)
{
PROFILE_FUNC();
for (ClipperLib::Path::iterator pit = polygon.begin(); pit != polygon.end(); ++pit) {
pit->X += CLIPPER_OFFSET_SCALE_ROUNDING_DELTA;
pit->Y += CLIPPER_OFFSET_SCALE_ROUNDING_DELTA;
pit->X >>= CLIPPER_OFFSET_POWER_OF_2;
pit->Y >>= CLIPPER_OFFSET_POWER_OF_2;
}
}
void unscaleClipperPolygons(ClipperLib::Paths &polygons)
{
PROFILE_FUNC();
for (ClipperLib::Paths::iterator it = polygons.begin(); it != polygons.end(); ++it)
for (ClipperLib::Path::iterator pit = (*it).begin(); pit != (*it).end(); ++pit) {
pit->X += CLIPPER_OFFSET_SCALE_ROUNDING_DELTA;
pit->Y += CLIPPER_OFFSET_SCALE_ROUNDING_DELTA;
pit->X >>= CLIPPER_OFFSET_POWER_OF_2;
pit->Y >>= CLIPPER_OFFSET_POWER_OF_2;
}
}
//-----------------------------------------------------------
// legacy code from Clipper documentation
void AddOuterPolyNodeToExPolygons(ClipperLib::PolyNode& polynode, ExPolygons* expolygons)
{
size_t cnt = expolygons->size();
expolygons->resize(cnt + 1);
(*expolygons)[cnt].contour = ClipperPath_to_Slic3rPolygon(polynode.Contour);
(*expolygons)[cnt].holes.resize(polynode.ChildCount());
for (int i = 0; i < polynode.ChildCount(); ++i)
{
(*expolygons)[cnt].holes[i] = ClipperPath_to_Slic3rPolygon(polynode.Childs[i]->Contour);
//Add outer polygons contained by (nested within) holes ...
for (int j = 0; j < polynode.Childs[i]->ChildCount(); ++j)
AddOuterPolyNodeToExPolygons(*polynode.Childs[i]->Childs[j], expolygons);
}
}
ExPolygons PolyTreeToExPolygons(ClipperLib::PolyTree& polytree)
{
ExPolygons retval;
for (int i = 0; i < polytree.ChildCount(); ++i)
AddOuterPolyNodeToExPolygons(*polytree.Childs[i], &retval);
return retval;
}
//-----------------------------------------------------------
Slic3r::Polygon ClipperPath_to_Slic3rPolygon(const ClipperLib::Path &input)
{
Polygon retval;
for (ClipperLib::Path::const_iterator pit = input.begin(); pit != input.end(); ++pit)
retval.points.emplace_back(pit->X, pit->Y);
return retval;
}
Slic3r::Polyline ClipperPath_to_Slic3rPolyline(const ClipperLib::Path &input)
{
Polyline retval;
for (ClipperLib::Path::const_iterator pit = input.begin(); pit != input.end(); ++pit)
retval.points.emplace_back(pit->X, pit->Y);
return retval;
}
Slic3r::Polygons ClipperPaths_to_Slic3rPolygons(const ClipperLib::Paths &input)
{
Slic3r::Polygons retval;
retval.reserve(input.size());
for (ClipperLib::Paths::const_iterator it = input.begin(); it != input.end(); ++it)
retval.emplace_back(ClipperPath_to_Slic3rPolygon(*it));
return retval;
}
Slic3r::Polylines ClipperPaths_to_Slic3rPolylines(const ClipperLib::Paths &input)
{
Slic3r::Polylines retval;
retval.reserve(input.size());
for (ClipperLib::Paths::const_iterator it = input.begin(); it != input.end(); ++it)
retval.emplace_back(ClipperPath_to_Slic3rPolyline(*it));
return retval;
}
ExPolygons ClipperPaths_to_Slic3rExPolygons(const ClipperLib::Paths &input)
{
// init Clipper
ClipperLib::Clipper clipper;
clipper.Clear();
// perform union
clipper.AddPaths(input, ClipperLib::ptSubject, true);
ClipperLib::PolyTree polytree;
clipper.Execute(ClipperLib::ctUnion, polytree, ClipperLib::pftEvenOdd, ClipperLib::pftEvenOdd); // offset results work with both EvenOdd and NonZero
// write to ExPolygons object
return PolyTreeToExPolygons(polytree);
}
ClipperLib::Path Slic3rMultiPoint_to_ClipperPath(const MultiPoint &input)
{
ClipperLib::Path retval;
for (Points::const_iterator pit = input.points.begin(); pit != input.points.end(); ++pit)
retval.emplace_back((*pit)(0), (*pit)(1));
return retval;
}
ClipperLib::Path Slic3rMultiPoint_to_ClipperPath_reversed(const Slic3r::MultiPoint &input)
{
ClipperLib::Path output;
output.reserve(input.points.size());
for (Slic3r::Points::const_reverse_iterator pit = input.points.rbegin(); pit != input.points.rend(); ++pit)
output.emplace_back((*pit)(0), (*pit)(1));
return output;
}
ClipperLib::Paths Slic3rMultiPoints_to_ClipperPaths(const Polygons &input)
{
ClipperLib::Paths retval;
for (Polygons::const_iterator it = input.begin(); it != input.end(); ++it)
retval.emplace_back(Slic3rMultiPoint_to_ClipperPath(*it));
return retval;
}
ClipperLib::Paths Slic3rMultiPoints_to_ClipperPaths(const ExPolygons &input)
{
ClipperLib::Paths retval;
for (auto &ep : input) {
retval.emplace_back(Slic3rMultiPoint_to_ClipperPath(ep.contour));
for (auto &h : ep.holes)
retval.emplace_back(Slic3rMultiPoint_to_ClipperPath(h));
}
return retval;
}
ClipperLib::Paths Slic3rMultiPoints_to_ClipperPaths(const Polylines &input)
{
ClipperLib::Paths retval;
for (Polylines::const_iterator it = input.begin(); it != input.end(); ++it)
retval.emplace_back(Slic3rMultiPoint_to_ClipperPath(*it));
return retval;
}
ClipperLib::Paths _offset(ClipperLib::Paths &&input, ClipperLib::EndType endType, const float delta, ClipperLib::JoinType joinType, double miterLimit)
{
// scale input
scaleClipperPolygons(input);
// perform offset
ClipperLib::ClipperOffset co;
if (joinType == jtRound)
co.ArcTolerance = miterLimit;
else
co.MiterLimit = miterLimit;
float delta_scaled = delta * float(CLIPPER_OFFSET_SCALE);
co.ShortestEdgeLength = double(std::abs(delta_scaled * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR));
co.AddPaths(input, joinType, endType);
ClipperLib::Paths retval;
co.Execute(retval, delta_scaled);
// unscale output
unscaleClipperPolygons(retval);
return retval;
}
ClipperLib::Paths _offset(ClipperLib::Path &&input, ClipperLib::EndType endType, const float delta, ClipperLib::JoinType joinType, double miterLimit)
{
ClipperLib::Paths paths;
paths.emplace_back(std::move(input));
return _offset(std::move(paths), endType, delta, joinType, miterLimit);
}
// This is a safe variant of the polygon offset, tailored for a single ExPolygon:
// a single polygon with multiple non-overlapping holes.
// Each contour and hole is offsetted separately, then the holes are subtracted from the outer contours.
ClipperLib::Paths _offset(const Slic3r::ExPolygon &expolygon, const float delta,
ClipperLib::JoinType joinType, double miterLimit)
{
// printf("new ExPolygon offset\n");
// 1) Offset the outer contour.
const float delta_scaled = delta * float(CLIPPER_OFFSET_SCALE);
ClipperLib::Paths contours;
{
ClipperLib::Path input = Slic3rMultiPoint_to_ClipperPath(expolygon.contour);
scaleClipperPolygon(input);
ClipperLib::ClipperOffset co;
if (joinType == jtRound)
co.ArcTolerance = miterLimit * double(CLIPPER_OFFSET_SCALE);
else
co.MiterLimit = miterLimit;
co.ShortestEdgeLength = double(std::abs(delta_scaled * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR));
co.AddPath(input, joinType, ClipperLib::etClosedPolygon);
co.Execute(contours, delta_scaled);
}
// 2) Offset the holes one by one, collect the results.
ClipperLib::Paths holes;
{
holes.reserve(expolygon.holes.size());
for (Polygons::const_iterator it_hole = expolygon.holes.begin(); it_hole != expolygon.holes.end(); ++ it_hole) {
ClipperLib::Path input = Slic3rMultiPoint_to_ClipperPath_reversed(*it_hole);
scaleClipperPolygon(input);
ClipperLib::ClipperOffset co;
if (joinType == jtRound)
co.ArcTolerance = miterLimit * double(CLIPPER_OFFSET_SCALE);
else
co.MiterLimit = miterLimit;
co.ShortestEdgeLength = double(std::abs(delta_scaled * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR));
co.AddPath(input, joinType, ClipperLib::etClosedPolygon);
ClipperLib::Paths out;
co.Execute(out, - delta_scaled);
holes.insert(holes.end(), out.begin(), out.end());
}
}
// 3) Subtract holes from the contours.
ClipperLib::Paths output;
if (holes.empty()) {
output = std::move(contours);
} else {
ClipperLib::Clipper clipper;
clipper.Clear();
clipper.AddPaths(contours, ClipperLib::ptSubject, true);
clipper.AddPaths(holes, ClipperLib::ptClip, true);
clipper.Execute(ClipperLib::ctDifference, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
}
// 4) Unscale the output.
unscaleClipperPolygons(output);
return output;
}
// This is a safe variant of the polygons offset, tailored for multiple ExPolygons.
// It is required, that the input expolygons do not overlap and that the holes of each ExPolygon don't intersect with their respective outer contours.
// Each ExPolygon is offsetted separately, then the offsetted ExPolygons are united.
ClipperLib::Paths _offset(const Slic3r::ExPolygons &expolygons, const float delta,
ClipperLib::JoinType joinType, double miterLimit)
{
const float delta_scaled = delta * float(CLIPPER_OFFSET_SCALE);
// Offsetted ExPolygons before they are united.
ClipperLib::Paths contours_cummulative;
contours_cummulative.reserve(expolygons.size());
// How many non-empty offsetted expolygons were actually collected into contours_cummulative?
// If only one, then there is no need to do a final union.
size_t expolygons_collected = 0;
for (Slic3r::ExPolygons::const_iterator it_expoly = expolygons.begin(); it_expoly != expolygons.end(); ++ it_expoly) {
// 1) Offset the outer contour.
ClipperLib::Paths contours;
{
ClipperLib::Path input = Slic3rMultiPoint_to_ClipperPath(it_expoly->contour);
scaleClipperPolygon(input);
ClipperLib::ClipperOffset co;
if (joinType == jtRound)
co.ArcTolerance = miterLimit * double(CLIPPER_OFFSET_SCALE);
else
co.MiterLimit = miterLimit;
co.ShortestEdgeLength = double(std::abs(delta_scaled * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR));
co.AddPath(input, joinType, ClipperLib::etClosedPolygon);
co.Execute(contours, delta_scaled);
}
if (contours.empty())
// No need to try to offset the holes.
continue;
if (it_expoly->holes.empty()) {
// No need to subtract holes from the offsetted expolygon, we are done.
contours_cummulative.insert(contours_cummulative.end(), contours.begin(), contours.end());
++ expolygons_collected;
} else {
// 2) Offset the holes one by one, collect the offsetted holes.
ClipperLib::Paths holes;
{
for (Polygons::const_iterator it_hole = it_expoly->holes.begin(); it_hole != it_expoly->holes.end(); ++ it_hole) {
ClipperLib::Path input = Slic3rMultiPoint_to_ClipperPath_reversed(*it_hole);
scaleClipperPolygon(input);
ClipperLib::ClipperOffset co;
if (joinType == jtRound)
co.ArcTolerance = miterLimit * double(CLIPPER_OFFSET_SCALE);
else
co.MiterLimit = miterLimit;
co.ShortestEdgeLength = double(std::abs(delta_scaled * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR));
co.AddPath(input, joinType, ClipperLib::etClosedPolygon);
ClipperLib::Paths out;
co.Execute(out, - delta_scaled);
holes.insert(holes.end(), out.begin(), out.end());
}
}
// 3) Subtract holes from the contours.
if (holes.empty()) {
// No hole remaining after an offset. Just copy the outer contour.
contours_cummulative.insert(contours_cummulative.end(), contours.begin(), contours.end());
++ expolygons_collected;
} else if (delta < 0) {
// Negative offset. There is a chance, that the offsetted hole intersects the outer contour.
// Subtract the offsetted holes from the offsetted contours.
ClipperLib::Clipper clipper;
clipper.Clear();
clipper.AddPaths(contours, ClipperLib::ptSubject, true);
clipper.AddPaths(holes, ClipperLib::ptClip, true);
ClipperLib::Paths output;
clipper.Execute(ClipperLib::ctDifference, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
if (! output.empty()) {
contours_cummulative.insert(contours_cummulative.end(), output.begin(), output.end());
++ expolygons_collected;
} else {
// The offsetted holes have eaten up the offsetted outer contour.
}
} else {
// Positive offset. As long as the Clipper offset does what one expects it to do, the offsetted hole will have a smaller
// area than the original hole or even disappear, therefore there will be no new intersections.
// Just collect the reversed holes.
contours_cummulative.reserve(contours.size() + holes.size());
contours_cummulative.insert(contours_cummulative.end(), contours.begin(), contours.end());
// Reverse the holes in place.
for (size_t i = 0; i < holes.size(); ++ i)
std::reverse(holes[i].begin(), holes[i].end());
contours_cummulative.insert(contours_cummulative.end(), holes.begin(), holes.end());
++ expolygons_collected;
}
}
}
// 4) Unite the offsetted expolygons.
ClipperLib::Paths output;
if (expolygons_collected > 1 && delta > 0) {
// There is a chance that the outwards offsetted expolygons may intersect. Perform a union.
ClipperLib::Clipper clipper;
clipper.Clear();
clipper.AddPaths(contours_cummulative, ClipperLib::ptSubject, true);
clipper.Execute(ClipperLib::ctUnion, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
} else {
// Negative offset. The shrunk expolygons shall not mutually intersect. Just copy the output.
output = std::move(contours_cummulative);
}
// 4) Unscale the output.
unscaleClipperPolygons(output);
return output;
}
ClipperLib::Paths
_offset2(const Polygons &polygons, const float delta1, const float delta2,
const ClipperLib::JoinType joinType, const double miterLimit)
{
// read input
ClipperLib::Paths input = Slic3rMultiPoints_to_ClipperPaths(polygons);
// scale input
scaleClipperPolygons(input);
// prepare ClipperOffset object
ClipperLib::ClipperOffset co;
if (joinType == jtRound) {
co.ArcTolerance = miterLimit;
} else {
co.MiterLimit = miterLimit;
}
float delta_scaled1 = delta1 * float(CLIPPER_OFFSET_SCALE);
float delta_scaled2 = delta2 * float(CLIPPER_OFFSET_SCALE);
co.ShortestEdgeLength = double(std::max(std::abs(delta_scaled1), std::abs(delta_scaled2)) * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR);
// perform first offset
ClipperLib::Paths output1;
co.AddPaths(input, joinType, ClipperLib::etClosedPolygon);
co.Execute(output1, delta_scaled1);
// perform second offset
co.Clear();
co.AddPaths(output1, joinType, ClipperLib::etClosedPolygon);
ClipperLib::Paths retval;
co.Execute(retval, delta_scaled2);
// unscale output
unscaleClipperPolygons(retval);
return retval;
}
Polygons
offset2(const Polygons &polygons, const float delta1, const float delta2,
const ClipperLib::JoinType joinType, const double miterLimit)
{
// perform offset
ClipperLib::Paths output = _offset2(polygons, delta1, delta2, joinType, miterLimit);
// convert into ExPolygons
return ClipperPaths_to_Slic3rPolygons(output);
}
ExPolygons
offset2_ex(const Polygons &polygons, const float delta1, const float delta2,
const ClipperLib::JoinType joinType, const double miterLimit)
{
// perform offset
ClipperLib::Paths output = _offset2(polygons, delta1, delta2, joinType, miterLimit);
// convert into ExPolygons
return ClipperPaths_to_Slic3rExPolygons(output);
}
//FIXME Vojtech: This functon may likely be optimized to avoid some of the Slic3r to Clipper
// conversions and unnecessary Clipper calls.
ExPolygons offset2_ex(const ExPolygons &expolygons, const float delta1,
const float delta2, ClipperLib::JoinType joinType, double miterLimit)
{
Polygons polys;
for (const ExPolygon &expoly : expolygons)
append(polys,
offset(offset_ex(expoly, delta1, joinType, miterLimit),
delta2, joinType, miterLimit));
return union_ex(polys);
}
template<class T, class TSubj, class TClip>
T _clipper_do(const ClipperLib::ClipType clipType,
TSubj && subject,
TClip && clip,
const ClipperLib::PolyFillType fillType,
const bool safety_offset_)
{
// read input
ClipperLib::Paths input_subject = Slic3rMultiPoints_to_ClipperPaths(std::forward<TSubj>(subject));
ClipperLib::Paths input_clip = Slic3rMultiPoints_to_ClipperPaths(std::forward<TClip>(clip));
// perform safety offset
if (safety_offset_) {
if (clipType == ClipperLib::ctUnion) {
safety_offset(&input_subject);
} else {
safety_offset(&input_clip);
}
}
// init Clipper
ClipperLib::Clipper clipper;
clipper.Clear();
// add polygons
clipper.AddPaths(input_subject, ClipperLib::ptSubject, true);
clipper.AddPaths(input_clip, ClipperLib::ptClip, true);
// perform operation
T retval;
clipper.Execute(clipType, retval, fillType, fillType);
return retval;
}
// Fix of #117: A large fractal pyramid takes ages to slice
// The Clipper library has difficulties processing overlapping polygons.
// Namely, the function ClipperLib::JoinCommonEdges() has potentially a terrible time complexity if the output
// of the operation is of the PolyTree type.
// This function implmenets a following workaround:
// 1) Peform the Clipper operation with the output to Paths. This method handles overlaps in a reasonable time.
// 2) Run Clipper Union once again to extract the PolyTree from the result of 1).
inline ClipperLib::PolyTree _clipper_do_polytree2(const ClipperLib::ClipType clipType, const Polygons &subject,
const Polygons &clip, const ClipperLib::PolyFillType fillType, const bool safety_offset_)
{
// read input
ClipperLib::Paths input_subject = Slic3rMultiPoints_to_ClipperPaths(subject);
ClipperLib::Paths input_clip = Slic3rMultiPoints_to_ClipperPaths(clip);
// perform safety offset
if (safety_offset_)
safety_offset((clipType == ClipperLib::ctUnion) ? &input_subject : &input_clip);
ClipperLib::Clipper clipper;
clipper.AddPaths(input_subject, ClipperLib::ptSubject, true);
clipper.AddPaths(input_clip, ClipperLib::ptClip, true);
// Perform the operation with the output to input_subject.
// This pass does not generate a PolyTree, which is a very expensive operation with the current Clipper library
// if there are overapping edges.
clipper.Execute(clipType, input_subject, fillType, fillType);
// Perform an additional Union operation to generate the PolyTree ordering.
clipper.Clear();
clipper.AddPaths(input_subject, ClipperLib::ptSubject, true);
ClipperLib::PolyTree retval;
clipper.Execute(ClipperLib::ctUnion, retval, fillType, fillType);
return retval;
}
ClipperLib::PolyTree _clipper_do_pl(const ClipperLib::ClipType clipType, const Polylines &subject,
const Polygons &clip, const ClipperLib::PolyFillType fillType,
const bool safety_offset_)
{
// read input
ClipperLib::Paths input_subject = Slic3rMultiPoints_to_ClipperPaths(subject);
ClipperLib::Paths input_clip = Slic3rMultiPoints_to_ClipperPaths(clip);
// perform safety offset
if (safety_offset_) safety_offset(&input_clip);
// init Clipper
ClipperLib::Clipper clipper;
clipper.Clear();
// add polygons
clipper.AddPaths(input_subject, ClipperLib::ptSubject, false);
clipper.AddPaths(input_clip, ClipperLib::ptClip, true);
// perform operation
ClipperLib::PolyTree retval;
clipper.Execute(clipType, retval, fillType, fillType);
return retval;
}
Polygons _clipper(ClipperLib::ClipType clipType, const Polygons &subject, const Polygons &clip, bool safety_offset_)
{
return ClipperPaths_to_Slic3rPolygons(_clipper_do<ClipperLib::Paths>(clipType, subject, clip, ClipperLib::pftNonZero, safety_offset_));
}
ExPolygons _clipper_ex(ClipperLib::ClipType clipType, const Polygons &subject, const Polygons &clip, bool safety_offset_)
{
ClipperLib::PolyTree polytree = _clipper_do_polytree2(clipType, subject, clip, ClipperLib::pftNonZero, safety_offset_);
return PolyTreeToExPolygons(polytree);
}
Polylines _clipper_pl(ClipperLib::ClipType clipType, const Polylines &subject, const Polygons &clip, bool safety_offset_)
{
ClipperLib::Paths output;
ClipperLib::PolyTreeToPaths(_clipper_do_pl(clipType, subject, clip, ClipperLib::pftNonZero, safety_offset_), output);
return ClipperPaths_to_Slic3rPolylines(output);
}
Polylines _clipper_pl(ClipperLib::ClipType clipType, const Polygons &subject, const Polygons &clip, bool safety_offset_)
{
// transform input polygons into polylines
Polylines polylines;
polylines.reserve(subject.size());
for (Polygons::const_iterator polygon = subject.begin(); polygon != subject.end(); ++polygon)
polylines.emplace_back(polygon->operator Polyline()); // implicit call to split_at_first_point()
// perform clipping
Polylines retval = _clipper_pl(clipType, polylines, clip, safety_offset_);
/* If the split_at_first_point() call above happens to split the polygon inside the clipping area
we would get two consecutive polylines instead of a single one, so we go through them in order
to recombine continuous polylines. */
for (size_t i = 0; i < retval.size(); ++i) {
for (size_t j = i+1; j < retval.size(); ++j) {
if (retval[i].points.back() == retval[j].points.front()) {
/* If last point of i coincides with first point of j,
append points of j to i and delete j */
retval[i].points.insert(retval[i].points.end(), retval[j].points.begin()+1, retval[j].points.end());
retval.erase(retval.begin() + j);
--j;
} else if (retval[i].points.front() == retval[j].points.back()) {
/* If first point of i coincides with last point of j,
prepend points of j to i and delete j */
retval[i].points.insert(retval[i].points.begin(), retval[j].points.begin(), retval[j].points.end()-1);
retval.erase(retval.begin() + j);
--j;
} else if (retval[i].points.front() == retval[j].points.front()) {
/* Since Clipper does not preserve orientation of polylines,
also check the case when first point of i coincides with first point of j. */
retval[j].reverse();
retval[i].points.insert(retval[i].points.begin(), retval[j].points.begin(), retval[j].points.end()-1);
retval.erase(retval.begin() + j);
--j;
} else if (retval[i].points.back() == retval[j].points.back()) {
/* Since Clipper does not preserve orientation of polylines,
also check the case when last point of i coincides with last point of j. */
retval[j].reverse();
retval[i].points.insert(retval[i].points.end(), retval[j].points.begin()+1, retval[j].points.end());
retval.erase(retval.begin() + j);
--j;
}
}
}
return retval;
}
Lines
_clipper_ln(ClipperLib::ClipType clipType, const Lines &subject, const Polygons &clip,
bool safety_offset_)
{
// convert Lines to Polylines
Polylines polylines;
polylines.reserve(subject.size());
for (const Line &line : subject)
polylines.emplace_back(Polyline(line.a, line.b));
// perform operation
polylines = _clipper_pl(clipType, polylines, clip, safety_offset_);
// convert Polylines to Lines
Lines retval;
for (Polylines::const_iterator polyline = polylines.begin(); polyline != polylines.end(); ++polyline)
retval.emplace_back(polyline->operator Line());
return retval;
}
ClipperLib::PolyTree union_pt(const Polygons &subject, bool safety_offset_)
{
return _clipper_do<ClipperLib::PolyTree>(ClipperLib::ctUnion, subject, Polygons(), ClipperLib::pftEvenOdd, safety_offset_);
}
ClipperLib::PolyTree union_pt(const ExPolygons &subject, bool safety_offset_)
{
return _clipper_do<ClipperLib::PolyTree>(ClipperLib::ctUnion, subject, Polygons(), ClipperLib::pftEvenOdd, safety_offset_);
}
ClipperLib::PolyTree union_pt(Polygons &&subject, bool safety_offset_)
{
return _clipper_do<ClipperLib::PolyTree>(ClipperLib::ctUnion, std::move(subject), Polygons(), ClipperLib::pftEvenOdd, safety_offset_);
}
ClipperLib::PolyTree union_pt(ExPolygons &&subject, bool safety_offset_)
{
return _clipper_do<ClipperLib::PolyTree>(ClipperLib::ctUnion, std::move(subject), Polygons(), ClipperLib::pftEvenOdd, safety_offset_);
}
// Simple spatial ordering of Polynodes
ClipperLib::PolyNodes order_nodes(const ClipperLib::PolyNodes &nodes)
{
// collect ordering points
Points ordering_points;
ordering_points.reserve(nodes.size());
for (const ClipperLib::PolyNode *node : nodes)
ordering_points.emplace_back(
Point(node->Contour.front().X, node->Contour.front().Y));
// perform the ordering
ClipperLib::PolyNodes ordered_nodes =
chain_clipper_polynodes(ordering_points, nodes);
return ordered_nodes;
}
static void traverse_pt_noholes(const ClipperLib::PolyNodes &nodes, Polygons *out)
{
foreach_node<e_ordering::ON>(nodes, [&out](const ClipperLib::PolyNode *node)
{
traverse_pt_noholes(node->Childs, out);
out->emplace_back(ClipperPath_to_Slic3rPolygon(node->Contour));
if (node->IsHole()) out->back().reverse(); // ccw
});
}
static void traverse_pt_old(ClipperLib::PolyNodes &nodes, Polygons* retval)
{
/* use a nearest neighbor search to order these children
TODO: supply start_near to chained_path() too? */
// collect ordering points
Points ordering_points;
ordering_points.reserve(nodes.size());
for (ClipperLib::PolyNodes::const_iterator it = nodes.begin(); it != nodes.end(); ++it) {
Point p((*it)->Contour.front().X, (*it)->Contour.front().Y);
ordering_points.push_back(p);
}
// perform the ordering
ClipperLib::PolyNodes ordered_nodes = chain_clipper_polynodes(ordering_points, nodes);
// push results recursively
for (ClipperLib::PolyNodes::iterator it = ordered_nodes.begin(); it != ordered_nodes.end(); ++it) {
// traverse the next depth
traverse_pt_old((*it)->Childs, retval);
retval->push_back(ClipperPath_to_Slic3rPolygon((*it)->Contour));
if ((*it)->IsHole()) retval->back().reverse(); // ccw
}
}
Polygons union_pt_chained(const Polygons &subject, bool safety_offset_)
{
ClipperLib::PolyTree polytree = union_pt(subject, safety_offset_);
Polygons retval;
traverse_pt_old(polytree.Childs, &retval);
return retval;
// TODO: This needs to be tested:
// ClipperLib::PolyTree polytree = union_pt(subject, safety_offset_);
// Polygons retval;
// traverse_pt_noholes(polytree.Childs, &retval);
// return retval;
}
Polygons simplify_polygons(const Polygons &subject, bool preserve_collinear)
{
// convert into Clipper polygons
ClipperLib::Paths input_subject = Slic3rMultiPoints_to_ClipperPaths(subject);
ClipperLib::Paths output;
if (preserve_collinear) {
ClipperLib::Clipper c;
c.PreserveCollinear(true);
c.StrictlySimple(true);
c.AddPaths(input_subject, ClipperLib::ptSubject, true);
c.Execute(ClipperLib::ctUnion, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
} else {
ClipperLib::SimplifyPolygons(input_subject, output, ClipperLib::pftNonZero);
}
// convert into Slic3r polygons
return ClipperPaths_to_Slic3rPolygons(output);
}
ExPolygons simplify_polygons_ex(const Polygons &subject, bool preserve_collinear)
{
if (! preserve_collinear)
return union_ex(simplify_polygons(subject, false));
// convert into Clipper polygons
ClipperLib::Paths input_subject = Slic3rMultiPoints_to_ClipperPaths(subject);
ClipperLib::PolyTree polytree;
ClipperLib::Clipper c;
c.PreserveCollinear(true);
c.StrictlySimple(true);
c.AddPaths(input_subject, ClipperLib::ptSubject, true);
c.Execute(ClipperLib::ctUnion, polytree, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
// convert into ExPolygons
return PolyTreeToExPolygons(polytree);
}
void safety_offset(ClipperLib::Paths* paths)
{
PROFILE_FUNC();
// scale input
scaleClipperPolygons(*paths);
// perform offset (delta = scale 1e-05)
ClipperLib::ClipperOffset co;
#ifdef CLIPPER_UTILS_DEBUG
if (clipper_export_enabled) {
static int iRun = 0;
export_clipper_input_polygons_bin(debug_out_path("safety_offset-polygons-%d", ++iRun).c_str(), *paths, ClipperLib::Paths());
}
#endif /* CLIPPER_UTILS_DEBUG */
ClipperLib::Paths out;
for (size_t i = 0; i < paths->size(); ++ i) {
ClipperLib::Path &path = (*paths)[i];
co.Clear();
co.MiterLimit = 2;
bool ccw = ClipperLib::Orientation(path);
if (! ccw)
std::reverse(path.begin(), path.end());
{
PROFILE_BLOCK(safety_offset_AddPaths);
co.AddPath((*paths)[i], ClipperLib::jtMiter, ClipperLib::etClosedPolygon);
}
{
PROFILE_BLOCK(safety_offset_Execute);
// offset outside by 10um
ClipperLib::Paths out_this;
co.Execute(out_this, ccw ? 10.f * float(CLIPPER_OFFSET_SCALE) : -10.f * float(CLIPPER_OFFSET_SCALE));
if (! ccw) {
// Reverse the resulting contours once again.
for (ClipperLib::Paths::iterator it = out_this.begin(); it != out_this.end(); ++ it)
std::reverse(it->begin(), it->end());
}
if (out.empty())
out = std::move(out_this);
else
std::move(std::begin(out_this), std::end(out_this), std::back_inserter(out));
}
}
*paths = std::move(out);
// unscale output
unscaleClipperPolygons(*paths);
}
Polygons top_level_islands(const Slic3r::Polygons &polygons)
{
// init Clipper
ClipperLib::Clipper clipper;
clipper.Clear();
// perform union
clipper.AddPaths(Slic3rMultiPoints_to_ClipperPaths(polygons), ClipperLib::ptSubject, true);
ClipperLib::PolyTree polytree;
clipper.Execute(ClipperLib::ctUnion, polytree, ClipperLib::pftEvenOdd, ClipperLib::pftEvenOdd);
// Convert only the top level islands to the output.
Polygons out;
out.reserve(polytree.ChildCount());
for (int i = 0; i < polytree.ChildCount(); ++i)
out.emplace_back(ClipperPath_to_Slic3rPolygon(polytree.Childs[i]->Contour));
return out;
}
// Outer offset shall not split the input contour into multiples. It is expected, that the solution will be non empty and it will contain just a single polygon.
ClipperLib::Paths fix_after_outer_offset(
const ClipperLib::Path &input,
// combination of default prameters to correspond to void ClipperOffset::Execute(Paths& solution, double delta)
// to produce a CCW output contour from CCW input contour for a positive offset.
ClipperLib::PolyFillType filltype, // = ClipperLib::pftPositive
bool reverse_result) // = false
{
ClipperLib::Paths solution;
if (! input.empty()) {
ClipperLib::Clipper clipper;
clipper.AddPath(input, ClipperLib::ptSubject, true);
clipper.ReverseSolution(reverse_result);
clipper.Execute(ClipperLib::ctUnion, solution, filltype, filltype);
}
return solution;
}
// Inner offset may split the source contour into multiple contours, but one resulting contour shall not lie inside the other.
ClipperLib::Paths fix_after_inner_offset(
const ClipperLib::Path &input,
// combination of default prameters to correspond to void ClipperOffset::Execute(Paths& solution, double delta)
// to produce a CCW output contour from CCW input contour for a negative offset.
ClipperLib::PolyFillType filltype, // = ClipperLib::pftNegative
bool reverse_result) // = true
{
ClipperLib::Paths solution;
if (! input.empty()) {
ClipperLib::Clipper clipper;
clipper.AddPath(input, ClipperLib::ptSubject, true);
ClipperLib::IntRect r = clipper.GetBounds();
r.left -= 10; r.top -= 10; r.right += 10; r.bottom += 10;
if (filltype == ClipperLib::pftPositive)
clipper.AddPath({ ClipperLib::IntPoint(r.left, r.bottom), ClipperLib::IntPoint(r.left, r.top), ClipperLib::IntPoint(r.right, r.top), ClipperLib::IntPoint(r.right, r.bottom) }, ClipperLib::ptSubject, true);
else
clipper.AddPath({ ClipperLib::IntPoint(r.left, r.bottom), ClipperLib::IntPoint(r.right, r.bottom), ClipperLib::IntPoint(r.right, r.top), ClipperLib::IntPoint(r.left, r.top) }, ClipperLib::ptSubject, true);
clipper.ReverseSolution(reverse_result);
clipper.Execute(ClipperLib::ctUnion, solution, filltype, filltype);
if (! solution.empty())
solution.erase(solution.begin());
}
return solution;
}
ClipperLib::Path mittered_offset_path_scaled(const Points &contour, const std::vector<float> &deltas, double miter_limit)
{
assert(contour.size() == deltas.size());
#ifndef NDEBUG
// Verify that the deltas are either all positive, or all negative.
bool positive = false;
bool negative = false;
for (float delta : deltas)
if (delta < 0.f)
negative = true;
else if (delta > 0.f)
positive = true;
assert(! (negative && positive));
#endif /* NDEBUG */
ClipperLib::Path out;
if (deltas.size() > 2)
{
out.reserve(contour.size() * 2);
// Clamp miter limit to 2.
miter_limit = (miter_limit > 2.) ? 2. / (miter_limit * miter_limit) : 0.5;
// perpenduclar vector
auto perp = [](const Vec2d &v) -> Vec2d { return Vec2d(v.y(), - v.x()); };
// Add a new point to the output, scale by CLIPPER_OFFSET_SCALE and round to ClipperLib::cInt.
auto add_offset_point = [&out](Vec2d pt) {
pt *= double(CLIPPER_OFFSET_SCALE);
pt += Vec2d(0.5 - (pt.x() < 0), 0.5 - (pt.y() < 0));
out.emplace_back(ClipperLib::cInt(pt.x()), ClipperLib::cInt(pt.y()));
};
// Minimum edge length, squared.
double lmin = *std::max_element(deltas.begin(), deltas.end()) * CLIPPER_OFFSET_SHORTEST_EDGE_FACTOR;
double l2min = lmin * lmin;
// Minimum angle to consider two edges to be parallel.
// Vojtech's estimate.
// const double sin_min_parallel = EPSILON + 1. / double(CLIPPER_OFFSET_SCALE);
// Implementation equal to Clipper.
const double sin_min_parallel = 1.;
// Find the last point further from pt by l2min.
Vec2d pt = contour.front().cast<double>();
size_t iprev = contour.size() - 1;
Vec2d ptprev;
for (; iprev > 0; -- iprev) {
ptprev = contour[iprev].cast<double>();
if ((ptprev - pt).squaredNorm() > l2min)
break;
}
if (iprev != 0) {
size_t ilast = iprev;
// Normal to the (pt - ptprev) segment.
Vec2d nprev = perp(pt - ptprev).normalized();
for (size_t i = 0; ; ) {
// Find the next point further from pt by l2min.
size_t j = i + 1;
Vec2d ptnext;
for (; j <= ilast; ++ j) {
ptnext = contour[j].cast<double>();
double l2 = (ptnext - pt).squaredNorm();
if (l2 > l2min)
break;
}
if (j > ilast) {
assert(i <= ilast);
// If the last edge is too short, merge it with the previous edge.
i = ilast;
ptnext = contour.front().cast<double>();
}
// Normal to the (ptnext - pt) segment.
Vec2d nnext = perp(ptnext - pt).normalized();
double delta = deltas[i];
double sin_a = clamp(-1., 1., cross2(nprev, nnext));
double convex = sin_a * delta;
if (convex <= - sin_min_parallel) {
// Concave corner.
add_offset_point(pt + nprev * delta);
add_offset_point(pt);
add_offset_point(pt + nnext * delta);
} else {
double dot = nprev.dot(nnext);
if (convex < sin_min_parallel && dot > 0.) {
// Nearly parallel.
add_offset_point((nprev.dot(nnext) > 0.) ? (pt + nprev * delta) : pt);
} else {
// Convex corner, possibly extremely sharp if convex < sin_min_parallel.
double r = 1. + dot;
if (r >= miter_limit)
add_offset_point(pt + (nprev + nnext) * (delta / r));
else {
double dx = std::tan(std::atan2(sin_a, dot) / 4.);
Vec2d newpt1 = pt + (nprev - perp(nprev) * dx) * delta;
Vec2d newpt2 = pt + (nnext + perp(nnext) * dx) * delta;
#ifndef NDEBUG
Vec2d vedge = 0.5 * (newpt1 + newpt2) - pt;
double dist_norm = vedge.norm();
assert(std::abs(dist_norm - std::abs(delta)) < SCALED_EPSILON);
#endif /* NDEBUG */
add_offset_point(newpt1);
add_offset_point(newpt2);
}
}
}
if (i == ilast)
break;
ptprev = pt;
nprev = nnext;
pt = ptnext;
i = j;
}
}
}
#if 0
{
ClipperLib::Path polytmp(out);
unscaleClipperPolygon(polytmp);
Slic3r::Polygon offsetted = ClipperPath_to_Slic3rPolygon(polytmp);
BoundingBox bbox = get_extents(contour);
bbox.merge(get_extents(offsetted));
static int iRun = 0;
SVG svg(debug_out_path("mittered_offset_path_scaled-%d.svg", iRun ++).c_str(), bbox);
svg.draw_outline(Polygon(contour), "blue", scale_(0.01));
svg.draw_outline(offsetted, "red", scale_(0.01));
svg.draw(contour, "blue", scale_(0.03));
svg.draw((Points)offsetted, "blue", scale_(0.03));
}
#endif
return out;
}
Polygons variable_offset_inner(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
{
#ifndef NDEBUG
// Verify that the deltas are all non positive.
for (const std::vector<float> &ds : deltas)
for (float delta : ds)
assert(delta <= 0.);
assert(expoly.holes.size() + 1 == deltas.size());
#endif /* NDEBUG */
// 1) Offset the outer contour.
ClipperLib::Paths contours = fix_after_inner_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftNegative, true);
#ifndef NDEBUG
for (auto &c : contours)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 2) Offset the holes one by one, collect the results.
ClipperLib::Paths holes;
holes.reserve(expoly.holes.size());
for (const Polygon& hole : expoly.holes)
append(holes, fix_after_outer_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftNegative, false));
#ifndef NDEBUG
for (auto &c : holes)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 3) Subtract holes from the contours.
ClipperLib::Paths output;
if (holes.empty())
output = std::move(contours);
else {
ClipperLib::Clipper clipper;
clipper.Clear();
clipper.AddPaths(contours, ClipperLib::ptSubject, true);
clipper.AddPaths(holes, ClipperLib::ptClip, true);
clipper.Execute(ClipperLib::ctDifference, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
}
// 4) Unscale the output.
unscaleClipperPolygons(output);
return ClipperPaths_to_Slic3rPolygons(output);
}
Polygons variable_offset_outer(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
{
#ifndef NDEBUG
// Verify that the deltas are all non positive.
for (const std::vector<float>& ds : deltas)
for (float delta : ds)
assert(delta >= 0.);
assert(expoly.holes.size() + 1 == deltas.size());
#endif /* NDEBUG */
// 1) Offset the outer contour.
ClipperLib::Paths contours = fix_after_outer_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftPositive, false);
#ifndef NDEBUG
for (auto &c : contours)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 2) Offset the holes one by one, collect the results.
ClipperLib::Paths holes;
holes.reserve(expoly.holes.size());
for (const Polygon& hole : expoly.holes)
append(holes, fix_after_inner_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftPositive, true));
#ifndef NDEBUG
for (auto &c : holes)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 3) Subtract holes from the contours.
ClipperLib::Paths output;
if (holes.empty())
output = std::move(contours);
else {
ClipperLib::Clipper clipper;
clipper.Clear();
clipper.AddPaths(contours, ClipperLib::ptSubject, true);
clipper.AddPaths(holes, ClipperLib::ptClip, true);
clipper.Execute(ClipperLib::ctDifference, output, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
}
// 4) Unscale the output.
unscaleClipperPolygons(output);
return ClipperPaths_to_Slic3rPolygons(output);
}
ExPolygons variable_offset_outer_ex(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
{
#ifndef NDEBUG
// Verify that the deltas are all non positive.
for (const std::vector<float>& ds : deltas)
for (float delta : ds)
assert(delta >= 0.);
assert(expoly.holes.size() + 1 == deltas.size());
#endif /* NDEBUG */
// 1) Offset the outer contour.
ClipperLib::Paths contours = fix_after_outer_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftPositive, false);
#ifndef NDEBUG
for (auto &c : contours)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 2) Offset the holes one by one, collect the results.
ClipperLib::Paths holes;
holes.reserve(expoly.holes.size());
for (const Polygon& hole : expoly.holes)
append(holes, fix_after_inner_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftPositive, true));
#ifndef NDEBUG
for (auto &c : holes)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 3) Subtract holes from the contours.
unscaleClipperPolygons(contours);
ExPolygons output;
if (holes.empty()) {
output.reserve(contours.size());
for (ClipperLib::Path &path : contours)
output.emplace_back(ClipperPath_to_Slic3rPolygon(path));
} else {
ClipperLib::Clipper clipper;
unscaleClipperPolygons(holes);
clipper.AddPaths(contours, ClipperLib::ptSubject, true);
clipper.AddPaths(holes, ClipperLib::ptClip, true);
ClipperLib::PolyTree polytree;
clipper.Execute(ClipperLib::ctDifference, polytree, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
output = PolyTreeToExPolygons(polytree);
}
return output;
}
ExPolygons variable_offset_inner_ex(const ExPolygon &expoly, const std::vector<std::vector<float>> &deltas, double miter_limit)
{
#ifndef NDEBUG
// Verify that the deltas are all non positive.
for (const std::vector<float>& ds : deltas)
for (float delta : ds)
assert(delta <= 0.);
assert(expoly.holes.size() + 1 == deltas.size());
#endif /* NDEBUG */
// 1) Offset the outer contour.
ClipperLib::Paths contours = fix_after_inner_offset(mittered_offset_path_scaled(expoly.contour.points, deltas.front(), miter_limit), ClipperLib::pftNegative, true);
#ifndef NDEBUG
for (auto &c : contours)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 2) Offset the holes one by one, collect the results.
ClipperLib::Paths holes;
holes.reserve(expoly.holes.size());
for (const Polygon& hole : expoly.holes)
append(holes, fix_after_outer_offset(mittered_offset_path_scaled(hole, deltas[1 + &hole - expoly.holes.data()], miter_limit), ClipperLib::pftNegative, false));
#ifndef NDEBUG
for (auto &c : holes)
assert(ClipperLib::Area(c) > 0.);
#endif /* NDEBUG */
// 3) Subtract holes from the contours.
unscaleClipperPolygons(contours);
ExPolygons output;
if (holes.empty()) {
output.reserve(contours.size());
for (ClipperLib::Path &path : contours)
output.emplace_back(ClipperPath_to_Slic3rPolygon(path));
} else {
ClipperLib::Clipper clipper;
unscaleClipperPolygons(holes);
clipper.AddPaths(contours, ClipperLib::ptSubject, true);
clipper.AddPaths(holes, ClipperLib::ptClip, true);
ClipperLib::PolyTree polytree;
clipper.Execute(ClipperLib::ctDifference, polytree, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
output = PolyTreeToExPolygons(polytree);
}
return output;
}
}
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