ENH: add arachne engine for narrow internal solid infill

ConcentricGapFill pattern was used for internal narrow
solid infill. Use arachne engine instead to remove
gap fill inside the pattern and improve the extrusion path

Signed-off-by: salt.wei <salt.wei@bambulab.com>
Change-Id: I758d7c72eb71cc37026b7cebf746cc345014c3f5
(cherry picked from commit 0b6bacd21a091afc13d7b36a69e5b10f155bc6f8)

src/libslic3r/Arachne/SkeletalTrapezoidationGraph.cpp

@@ -0,0 +1,467 @@
+//Copyright (c) 2020 Ultimaker B.V.
+//CuraEngine is released under the terms of the AGPLv3 or higher.
+
+#include "SkeletalTrapezoidationGraph.hpp"
+#include <unordered_map>
+
+#include <boost/log/trivial.hpp>
+
+#include "utils/linearAlg2D.hpp"
+#include "../Line.hpp"
+
+namespace Slic3r::Arachne
+{
+
+STHalfEdge::STHalfEdge(SkeletalTrapezoidationEdge data) : HalfEdge(data) {}
+
+bool STHalfEdge::canGoUp(bool strict) const
+{
+    if (to->data.distance_to_boundary > from->data.distance_to_boundary)
+    {
+        return true;
+    }
+    if (to->data.distance_to_boundary < from->data.distance_to_boundary || strict)
+    {
+        return false;
+    }
+
+    // Edge is between equidistqant verts; recurse!
+    for (edge_t* outgoing = next; outgoing != twin; outgoing = outgoing->twin->next)
+    {
+        if (outgoing->canGoUp())
+        {
+            return true;
+        }
+        assert(outgoing->twin); if (!outgoing->twin) return false;
+        assert(outgoing->twin->next); if (!outgoing->twin->next) return true; // This point is on the boundary?! Should never occur
+    }
+    return false;
+}
+
+bool STHalfEdge::isUpward() const
+{
+    if (to->data.distance_to_boundary > from->data.distance_to_boundary)
+    {
+        return true;
+    }
+    if (to->data.distance_to_boundary < from->data.distance_to_boundary)
+    {
+        return false;
+    }
+
+    // Equidistant edge case:
+    std::optional<coord_t> forward_up_dist = this->distToGoUp();
+    std::optional<coord_t> backward_up_dist = twin->distToGoUp();
+    if (forward_up_dist && backward_up_dist)
+    {
+        return forward_up_dist < backward_up_dist;
+    }
+
+    if (forward_up_dist)
+    {
+        return true;
+    }
+
+    if (backward_up_dist)
+    {
+        return false;
+    }
+    return to->p < from->p; // Arbitrary ordering, which returns the opposite for the twin edge
+}
+
+std::optional<coord_t> STHalfEdge::distToGoUp() const
+{
+    if (to->data.distance_to_boundary > from->data.distance_to_boundary)
+    {
+        return 0;
+    }
+    if (to->data.distance_to_boundary < from->data.distance_to_boundary)
+    {
+        return std::optional<coord_t>();
+    }
+
+    // Edge is between equidistqant verts; recurse!
+    std::optional<coord_t> ret;
+    for (edge_t* outgoing = next; outgoing != twin; outgoing = outgoing->twin->next)
+    {
+        std::optional<coord_t> dist_to_up = outgoing->distToGoUp();
+        if (dist_to_up)
+        {
+            if (ret)
+            {
+                ret = std::min(*ret, *dist_to_up);
+            }
+            else
+            {
+                ret = dist_to_up;
+            }
+        }
+        assert(outgoing->twin); if (!outgoing->twin) return std::optional<coord_t>();
+        assert(outgoing->twin->next); if (!outgoing->twin->next) return 0; // This point is on the boundary?! Should never occur
+    }
+    if (ret)
+    {
+        ret = *ret + (to->p - from->p).cast<int64_t>().norm();
+    }
+    return ret;
+}
+
+STHalfEdge* STHalfEdge::getNextUnconnected()
+{
+    edge_t* result = static_cast<STHalfEdge*>(this);
+    while (result->next)
+    {
+        result = result->next;
+        if (result == this)
+        {
+            return nullptr;
+        }
+    }
+    return result->twin;
+}
+
+STHalfEdgeNode::STHalfEdgeNode(SkeletalTrapezoidationJoint data, Point p) : HalfEdgeNode(data, p) {}
+
+bool STHalfEdgeNode::isMultiIntersection()
+{
+    int odd_path_count = 0;
+    edge_t* outgoing = this->incident_edge;
+    do
+    {
+        if ( ! outgoing)
+        { // This is a node on the outside
+            return false;
+        }
+        if (outgoing->data.isCentral())
+        {
+            odd_path_count++;
+        }
+    } while (outgoing = outgoing->twin->next, outgoing != this->incident_edge);
+    return odd_path_count > 2;
+}
+
+bool STHalfEdgeNode::isCentral() const
+{
+    edge_t* edge = incident_edge;
+    do
+    {
+        if (edge->data.isCentral())
+        {
+            return true;
+        }
+        assert(edge->twin); if (!edge->twin) return false;
+    } while (edge = edge->twin->next, edge != incident_edge);
+    return false;
+}
+
+bool STHalfEdgeNode::isLocalMaximum(bool strict) const
+{
+    if (data.distance_to_boundary == 0)
+    {
+        return false;
+    }
+
+    edge_t* edge = incident_edge;
+    do
+    {
+        if (edge->canGoUp(strict))
+        {
+            return false;
+        }
+        assert(edge->twin); if (!edge->twin) return false;
+
+        if (!edge->twin->next)
+        { // This point is on the boundary
+            return false;
+        }
+    } while (edge = edge->twin->next, edge != incident_edge);
+    return true;
+}
+
+void SkeletalTrapezoidationGraph::collapseSmallEdges(coord_t snap_dist)
+{
+    std::unordered_map<edge_t*, std::list<edge_t>::iterator> edge_locator;
+    std::unordered_map<node_t*, std::list<node_t>::iterator> node_locator;
+    
+    for (auto edge_it = edges.begin(); edge_it != edges.end(); ++edge_it)
+    {
+        edge_locator.emplace(&*edge_it, edge_it);
+    }
+    
+    for (auto node_it = nodes.begin(); node_it != nodes.end(); ++node_it)
+    {
+        node_locator.emplace(&*node_it, node_it);
+    }
+    
+    auto safelyRemoveEdge = [this, &edge_locator](edge_t* to_be_removed, std::list<edge_t>::iterator& current_edge_it, bool& edge_it_is_updated)
+    {
+        if (current_edge_it != edges.end()
+            && to_be_removed == &*current_edge_it)
+        {
+            current_edge_it = edges.erase(current_edge_it);
+            edge_it_is_updated = true;
+        }
+        else
+        {
+            edges.erase(edge_locator[to_be_removed]);
+        }
+    };
+
+    auto should_collapse = [snap_dist](node_t* a, node_t* b) 
+    { 
+        return shorter_then(a->p - b->p, snap_dist);
+    };
+        
+    for (auto edge_it = edges.begin(); edge_it != edges.end();)
+    {
+        if (edge_it->prev)
+        {
+            edge_it++;
+            continue;
+        }
+        
+        edge_t* quad_start = &*edge_it;
+        edge_t* quad_end = quad_start; while (quad_end->next) quad_end = quad_end->next;
+        edge_t* quad_mid = (quad_start->next == quad_end)? nullptr : quad_start->next;
+
+        bool edge_it_is_updated = false;
+        if (quad_mid && should_collapse(quad_mid->from, quad_mid->to))
+        {
+            assert(quad_mid->twin);
+            if(!quad_mid->twin)
+            {
+                BOOST_LOG_TRIVIAL(warning) << "Encountered quad edge without a twin.";
+                continue; //Prevent accessing unallocated memory.
+            }
+            int count = 0;
+            for (edge_t* edge_from_3 = quad_end; edge_from_3 && edge_from_3 != quad_mid->twin; edge_from_3 = edge_from_3->twin->next)
+            {
+                edge_from_3->from = quad_mid->from;
+                edge_from_3->twin->to = quad_mid->from;
+                if (count > 50)
+                {
+                    std::cerr << edge_from_3->from->p << " - " << edge_from_3->to->p << '\n';
+                }
+                if (++count > 1000) 
+                {
+                    break;
+                }
+            }
+
+            // o-o > collapse top
+            // | |
+            // | |
+            // | |
+            // o o
+            if (quad_mid->from->incident_edge == quad_mid)
+            {
+                if (quad_mid->twin->next)
+                {
+                    quad_mid->from->incident_edge = quad_mid->twin->next;
+                }
+                else
+                {
+                    quad_mid->from->incident_edge = quad_mid->prev->twin;
+                }
+            }
+            
+            nodes.erase(node_locator[quad_mid->to]);
+
+            quad_mid->prev->next = quad_mid->next;
+            quad_mid->next->prev = quad_mid->prev;
+            quad_mid->twin->next->prev = quad_mid->twin->prev;
+            quad_mid->twin->prev->next = quad_mid->twin->next;
+
+            safelyRemoveEdge(quad_mid->twin, edge_it, edge_it_is_updated);
+            safelyRemoveEdge(quad_mid, edge_it, edge_it_is_updated);
+        }
+
+        //  o-o
+        //  | | > collapse sides
+        //  o o
+        if ( should_collapse(quad_start->from, quad_end->to) && should_collapse(quad_start->to, quad_end->from))
+        { // Collapse start and end edges and remove whole cell
+
+            quad_start->twin->to = quad_end->to;
+            quad_end->to->incident_edge = quad_end->twin;
+            if (quad_end->from->incident_edge == quad_end)
+            {
+                if (quad_end->twin->next)
+                {
+                    quad_end->from->incident_edge = quad_end->twin->next;
+                }
+                else
+                {
+                    quad_end->from->incident_edge = quad_end->prev->twin;
+                }
+            }
+            nodes.erase(node_locator[quad_start->from]);
+
+            quad_start->twin->twin = quad_end->twin;
+            quad_end->twin->twin = quad_start->twin;
+            safelyRemoveEdge(quad_start, edge_it, edge_it_is_updated);
+            safelyRemoveEdge(quad_end, edge_it, edge_it_is_updated);
+        }
+        // If only one side had collapsable length then the cell on the other side of that edge has to collapse
+        // if we would collapse that one edge then that would change the quad_start and/or quad_end of neighboring cells
+        // this is to do with the constraint that !prev == !twin.next
+
+        if (!edge_it_is_updated)
+        {
+            edge_it++;
+        }
+    }
+}
+
+void SkeletalTrapezoidationGraph::makeRib(edge_t*& prev_edge, Point start_source_point, Point end_source_point, bool is_next_to_start_or_end)
+{
+    Point p;
+    Line(start_source_point, end_source_point).distance_to_infinite_squared(prev_edge->to->p, &p);
+    coord_t dist = (prev_edge->to->p - p).cast<int64_t>().norm();
+    prev_edge->to->data.distance_to_boundary = dist;
+    assert(dist >= 0);
+
+    nodes.emplace_front(SkeletalTrapezoidationJoint(), p);
+    node_t* node = &nodes.front();
+    node->data.distance_to_boundary = 0;
+    
+    edges.emplace_front(SkeletalTrapezoidationEdge(SkeletalTrapezoidationEdge::EdgeType::EXTRA_VD));
+    edge_t* forth_edge = &edges.front();
+    edges.emplace_front(SkeletalTrapezoidationEdge(SkeletalTrapezoidationEdge::EdgeType::EXTRA_VD));
+    edge_t* back_edge = &edges.front();
+    
+    prev_edge->next = forth_edge;
+    forth_edge->prev = prev_edge;
+    forth_edge->from = prev_edge->to;
+    forth_edge->to = node;
+    forth_edge->twin = back_edge;
+    back_edge->twin = forth_edge;
+    back_edge->from = node;
+    back_edge->to = prev_edge->to;
+    node->incident_edge = back_edge;
+    
+    prev_edge = back_edge;
+}
+
+std::pair<SkeletalTrapezoidationGraph::edge_t*, SkeletalTrapezoidationGraph::edge_t*> SkeletalTrapezoidationGraph::insertRib(edge_t& edge, node_t* mid_node)
+{
+    edge_t* edge_before = edge.prev;
+    edge_t* edge_after = edge.next;
+    node_t* node_before = edge.from;
+    node_t* node_after = edge.to;
+    
+    Point p = mid_node->p;
+
+    const Line source_segment = getSource(edge);
+    Point      px;
+    source_segment.distance_to_squared(p, &px);
+    coord_t dist = (p - px).cast<int64_t>().norm();
+    assert(dist > 0);
+    mid_node->data.distance_to_boundary = dist;
+    mid_node->data.transition_ratio = 0; // Both transition end should have rest = 0, because at the ends a whole number of beads fits without rest
+
+    nodes.emplace_back(SkeletalTrapezoidationJoint(), px);
+    node_t* source_node = &nodes.back();
+    source_node->data.distance_to_boundary = 0;
+
+    edge_t* first = &edge;
+    edges.emplace_back(SkeletalTrapezoidationEdge());
+    edge_t* second = &edges.back();
+    edges.emplace_back(SkeletalTrapezoidationEdge(SkeletalTrapezoidationEdge::EdgeType::TRANSITION_END));
+    edge_t* outward_edge = &edges.back();
+    edges.emplace_back(SkeletalTrapezoidationEdge(SkeletalTrapezoidationEdge::EdgeType::TRANSITION_END));
+    edge_t* inward_edge = &edges.back();
+
+    if (edge_before)
+    {
+        edge_before->next = first;
+    }
+    first->next = outward_edge;
+    outward_edge->next = nullptr;
+    inward_edge->next = second;
+    second->next = edge_after;
+
+    if (edge_after) 
+    {
+        edge_after->prev = second;
+    }
+    second->prev = inward_edge;
+    inward_edge->prev = nullptr;
+    outward_edge->prev = first;
+    first->prev = edge_before;
+
+    first->to = mid_node;
+    outward_edge->to = source_node;
+    inward_edge->to = mid_node;
+    second->to = node_after;
+
+    first->from = node_before;
+    outward_edge->from = mid_node;
+    inward_edge->from = source_node;
+    second->from = mid_node;
+
+    node_before->incident_edge = first;
+    mid_node->incident_edge = outward_edge;
+    source_node->incident_edge = inward_edge;
+    if (edge_after) 
+    {
+        node_after->incident_edge = edge_after;
+    }
+
+    first->data.setIsCentral(true);
+    outward_edge->data.setIsCentral(false); // TODO verify this is always the case.
+    inward_edge->data.setIsCentral(false);
+    second->data.setIsCentral(true);
+
+    outward_edge->twin = inward_edge;
+    inward_edge->twin = outward_edge;
+
+    first->twin = nullptr; // we don't know these yet!
+    second->twin = nullptr;
+
+    assert(second->prev->from->data.distance_to_boundary == 0);
+
+    return std::make_pair(first, second);
+}
+
+SkeletalTrapezoidationGraph::edge_t* SkeletalTrapezoidationGraph::insertNode(edge_t* edge, Point mid, coord_t mide_node_bead_count)
+{
+    edge_t* last_edge_replacing_input = edge;
+
+    nodes.emplace_back(SkeletalTrapezoidationJoint(), mid);
+    node_t* mid_node = &nodes.back();
+
+    edge_t* twin = last_edge_replacing_input->twin;
+    last_edge_replacing_input->twin = nullptr;
+    twin->twin = nullptr;
+    std::pair<edge_t*, edge_t*> left_pair = insertRib(*last_edge_replacing_input, mid_node);
+    std::pair<edge_t*, edge_t*> right_pair = insertRib(*twin, mid_node);
+    edge_t* first_edge_replacing_input = left_pair.first;
+    last_edge_replacing_input = left_pair.second;
+    edge_t* first_edge_replacing_twin = right_pair.first;
+    edge_t* last_edge_replacing_twin = right_pair.second;
+
+    first_edge_replacing_input->twin = last_edge_replacing_twin;
+    last_edge_replacing_twin->twin = first_edge_replacing_input;
+    last_edge_replacing_input->twin = first_edge_replacing_twin;
+    first_edge_replacing_twin->twin = last_edge_replacing_input;
+
+    mid_node->data.bead_count = mide_node_bead_count;
+
+    return last_edge_replacing_input;
+}
+
+Line SkeletalTrapezoidationGraph::getSource(const edge_t &edge) const
+{
+    const edge_t *from_edge = &edge;
+    while (from_edge->prev)
+        from_edge = from_edge->prev;
+
+    const edge_t *to_edge = &edge;
+    while (to_edge->next)
+        to_edge = to_edge->next;
+
+    return Line(from_edge->from->p, to_edge->to->p);
+}
+
+}