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Rest of the path chaining has been replaced with the new algorithm.

Browse source 
PolylineCollection.cpp/hpp was removed, use Polylines instead.
Various first_point() / last_point() now return references, not copies.
This commit is contained in:
bubnikv 2019-09-27 18:17:21 +02:00
parent 4b35ebe6e5
commit 331c187b39
29 changed files with 266 additions and 364 deletions
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146
src/libslic3r/ShortestPath.cpp
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@ -14,6 +14,44 @@
namespace Slic3r {
// Naive implementation of the Traveling Salesman Problem, it works by always taking the next closest neighbor.
// This implementation will always produce valid result even if some segments cannot reverse.
template<typename EndPointType, typename KDTreeType, typename CouldReverseFunc>
std::vector<std::pair<size_t, bool>> chain_segments_closest_point(std::vector<EndPointType> &end_points, KDTreeType &kdtree, CouldReverseFunc &could_reverse_func, EndPointType &first_point)
{
assert((end_points.size() & 1) == 0);
size_t num_segments = end_points.size() / 2;
assert(num_segments >= 2);
for (EndPointType &ep : end_points)
ep.chain_id = 0;
std::vector<std::pair<size_t, bool>> out;
out.reserve(num_segments);
size_t first_point_idx = &first_point - end_points.data();
out.emplace_back(first_point_idx / 2, (first_point_idx & 1) != 0);
first_point.chain_id = 1;
size_t this_idx = first_point_idx ^ 1;
for (int iter = (int)num_segments - 2; iter >= 0; -- iter) {
EndPointType &this_point = end_points[this_idx];
this_point.chain_id = 1;
// Find the closest point to this end_point, which lies on a different extrusion path (filtered by the lambda).
// Ignore the starting point as the starting point is considered to be occupied, no end point coud connect to it.
size_t next_idx = find_closest_point(kdtree, this_point.pos,
[this_idx, &end_points, &could_reverse_func](size_t idx) {
return (idx ^ this_idx) > 1 && end_points[idx].chain_id == 0 && ((idx ^ 1) == 0 || could_reverse_func(idx >> 1));
});
assert(next_idx < end_points.size());
EndPointType &end_point = end_points[next_idx];
end_point.chain_id = 1;
this_idx = next_idx ^ 1;
}
#ifndef _NDEBUG
assert(end_points[this_idx].chain_id == 0);
for (EndPointType &ep : end_points)
assert(&ep == &end_points[this_idx] || ep.chain_id == 1);
#endif /* _NDEBUG */
return out;
}
// Chain perimeters (always closed) and thin fills (closed or open) using a greedy algorithm.
// Solving a Traveling Salesman Problem (TSP) with the modification, that the sites are not always points, but points and segments.
// Solving using a greedy algorithm, where a shortest edge is added to the solution if it does not produce a bifurcation or a cycle.
@ -22,8 +60,8 @@ namespace Slic3r {
// The algorithm builds a tour for the traveling salesman one edge at a time and thus maintains multiple tour fragments, each of which
// is a simple path in the complete graph of cities. At each stage, the algorithm selects the edge of minimal cost that either creates
// a new fragment, extends one of the existing paths or creates a cycle of length equal to the number of cities.
template<typename PointType, typename SegmentEndPointFunc>
std::vector<std::pair<size_t, bool>> chain_segments(SegmentEndPointFunc end_point_func, size_t num_segments, const PointType *start_near)
template<typename PointType, typename SegmentEndPointFunc, bool REVERSE_COULD_FAIL, typename CouldReverseFunc>
std::vector<std::pair<size_t, bool>> chain_segments_greedy_constrained_reversals_(SegmentEndPointFunc end_point_func, CouldReverseFunc could_reverse_func, size_t num_segments, const PointType *start_near)
{
std::vector<std::pair<size_t, bool>> out;
@ -132,6 +170,8 @@ std::vector<std::pair<size_t, bool>> chain_segments(SegmentEndPointFunc end_poin
first_point->chain_id = equivalent_chain.next();
first_point_idx = idx;
}
EndPoint *initial_point = first_point;
EndPoint *last_point = nullptr;
// Assign the closest point and distance to the end points.
for (EndPoint &end_point : end_points) {
@ -240,12 +280,15 @@ std::vector<std::pair<size_t, bool>> chain_segments(SegmentEndPointFunc end_poin
if (iter == 0) {
// Last iteration. There shall be exactly one or two end points waiting to be connected.
assert(queue.size() == ((first_point == nullptr) ? 2 : 1));
if (first_point == nullptr)
if (first_point == nullptr) {
first_point = queue.top();
while (! queue.empty()) {
queue.top()->edge_out = nullptr;
queue.pop();
first_point->edge_out = nullptr;
}
last_point = queue.top();
last_point->edge_out = nullptr;
queue.pop();
assert(queue.empty());
break;
}
} else {
@ -280,24 +323,77 @@ std::vector<std::pair<size_t, bool>> chain_segments(SegmentEndPointFunc end_poin
// Now interconnect pairs of segments into a chain.
assert(first_point != nullptr);
out.reserve(num_segments);
bool failed = false;
do {
assert(out.size() < num_segments);
size_t first_point_id = first_point - &end_points.front();
size_t segment_id = first_point_id >> 1;
bool reverse = (first_point_id & 1) != 0;
EndPoint *second_point = &end_points[first_point_id ^ 1];
out.emplace_back(segment_id, (first_point_id & 1) != 0);
if (REVERSE_COULD_FAIL) {
if (reverse && ! could_reverse_func(segment_id)) {
failed = true;
break;
}
} else {
assert(! reverse || could_reverse_func(segment_id));
}
out.emplace_back(segment_id, reverse);
first_point = second_point->edge_out;
} while (first_point != nullptr);
if (REVERSE_COULD_FAIL) {
if (failed) {
if (start_near == nullptr) {
// We may try the reverse order.
out.clear();
first_point = last_point;
failed = false;
do {
assert(out.size() < num_segments);
size_t first_point_id = first_point - &end_points.front();
size_t segment_id = first_point_id >> 1;
bool reverse = (first_point_id & 1) != 0;
EndPoint *second_point = &end_points[first_point_id ^ 1];
if (reverse && ! could_reverse_func(segment_id)) {
failed = true;
break;
}
out.emplace_back(segment_id, reverse);
first_point = second_point->edge_out;
} while (first_point != nullptr);
}
}
if (failed)
// As a last resort, try a dumb algorithm, which is not sensitive to edge reversal constraints.
out = chain_segments_closest_point<EndPoint, decltype(kdtree), CouldReverseFunc>(end_points, kdtree, could_reverse_func, (initial_point != nullptr) ? *initial_point : end_points.front());
} else {
assert(! failed);
}
}
assert(out.size() == num_segments);
return out;
}
template<typename PointType, typename SegmentEndPointFunc, typename CouldReverseFunc>
std::vector<std::pair<size_t, bool>> chain_segments_greedy_constrained_reversals(SegmentEndPointFunc end_point_func, CouldReverseFunc could_reverse_func, size_t num_segments, const PointType *start_near)
{
return chain_segments_greedy_constrained_reversals_<PointType, SegmentEndPointFunc, true, CouldReverseFunc>(end_point_func, could_reverse_func, num_segments, start_near);
}
template<typename PointType, typename SegmentEndPointFunc>
std::vector<std::pair<size_t, bool>> chain_segments_greedy(SegmentEndPointFunc end_point_func, size_t num_segments, const PointType *start_near)
{
auto could_reverse_func = [](size_t /* idx */) -> bool { return true; };
return chain_segments_greedy_constrained_reversals_<PointType, SegmentEndPointFunc, false, decltype(could_reverse_func)>(end_point_func, could_reverse_func, num_segments, start_near);
}
std::vector<std::pair<size_t, bool>> chain_extrusion_entities(std::vector<ExtrusionEntity*> &entities, const Point *start_near)
{
auto segment_end_point = [&entities](size_t idx, bool first_point) -> const Point& { return first_point ? entities[idx]->first_point() : entities[idx]->last_point(); };
std::vector<std::pair<size_t, bool>> out = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, entities.size(), start_near);
auto could_reverse = [&entities](size_t idx) { const ExtrusionEntity *ee = entities[idx]; return ee->is_loop() || ee->can_reverse(); };
std::vector<std::pair<size_t, bool>> out = chain_segments_greedy_constrained_reversals<Point, decltype(segment_end_point), decltype(could_reverse)>(segment_end_point, could_reverse, entities.size(), start_near);
for (size_t i = 0; i < entities.size(); ++ i) {
ExtrusionEntity *ee = entities[i];
if (ee->is_loop())
@ -328,10 +424,34 @@ void chain_and_reorder_extrusion_entities(std::vector<ExtrusionEntity*> &entitie
reorder_extrusion_entities(entities, chain_extrusion_entities(entities, start_near));
}
std::vector<std::pair<size_t, bool>> chain_extrusion_paths(std::vector<ExtrusionPath> &extrusion_paths, const Point *start_near)
{
auto segment_end_point = [&extrusion_paths](size_t idx, bool first_point) -> const Point& { return first_point ? extrusion_paths[idx].first_point() : extrusion_paths[idx].last_point(); };
return chain_segments_greedy<Point, decltype(segment_end_point)>(segment_end_point, extrusion_paths.size(), start_near);
}
void reorder_extrusion_paths(std::vector<ExtrusionPath> &extrusion_paths, std::vector<std::pair<size_t, bool>> &chain)
{
assert(extrusion_paths.size() == chain.size());
std::vector<ExtrusionPath> out;
out.reserve(extrusion_paths.size());
for (const std::pair<size_t, bool> &idx : chain) {
out.emplace_back(std::move(extrusion_paths[idx.first]));
if (idx.second)
out.back().reverse();
}
extrusion_paths.swap(out);
}
void chain_and_reorder_extrusion_paths(std::vector<ExtrusionPath> &extrusion_paths, const Point *start_near)
{
reorder_extrusion_paths(extrusion_paths, chain_extrusion_paths(extrusion_paths, start_near));
}
std::vector<size_t> chain_points(const Points &points, Point *start_near)
{
auto segment_end_point = [&points](size_t idx, bool /* first_point */) -> const Point& { return points[idx]; };
std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, points.size(), start_near);
std::vector<std::pair<size_t, bool>> ordered = chain_segments_greedy<Point, decltype(segment_end_point)>(segment_end_point, points.size(), start_near);
std::vector<size_t> out;
out.reserve(ordered.size());
for (auto &segment_and_reversal : ordered)
@ -339,12 +459,12 @@ std::vector<size_t> chain_points(const Points &points, Point *start_near)
return out;
}
Polylines chain_infill_polylines(Polylines &polylines)
Polylines chain_polylines(Polylines &polylines, const Point *start_near)
{
auto segment_end_point = [&polylines](size_t idx, bool first_point) -> const Point& { return first_point ? polylines[idx].first_point() : polylines[idx].last_point(); };
std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, polylines.size(), nullptr);
std::vector<std::pair<size_t, bool>> ordered = chain_segments_greedy<Point, decltype(segment_end_point)>(segment_end_point, polylines.size(), start_near);
Polylines out;
out.reserve(polylines.size());
out.reserve(polylines.size());
for (auto &segment_and_reversal : ordered) {
out.emplace_back(std::move(polylines[segment_and_reversal.first]));
if (segment_and_reversal.second)
@ -356,7 +476,7 @@ Polylines chain_infill_polylines(Polylines &polylines)
template<class T> static inline T chain_path_items(const Points &points, const T &items)
{
auto segment_end_point = [&points](size_t idx, bool /* first_point */) -> const Point& { return points[idx]; };
std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, points.size(), nullptr);
std::vector<std::pair<size_t, bool>> ordered = chain_segments_greedy<Point, decltype(segment_end_point)>(segment_end_point, points.size(), nullptr);
T out;
out.reserve(items.size());
for (auto &segment_and_reversal : ordered)
@ -382,7 +502,7 @@ std::vector<std::pair<size_t, size_t>> chain_print_object_instances(const Print
}
}
auto segment_end_point = [&object_reference_points](size_t idx, bool /* first_point */) -> const Point& { return object_reference_points[idx]; };
std::vector<std::pair<size_t, bool>> ordered = chain_segments<Point, decltype(segment_end_point)>(segment_end_point, instances.size(), nullptr);
std::vector<std::pair<size_t, bool>> ordered = chain_segments_greedy<Point, decltype(segment_end_point)>(segment_end_point, instances.size(), nullptr);
std::vector<std::pair<size_t, size_t>> out;
out.reserve(instances.size());
for (auto &segment_and_reversal : ordered)