OrcaSlicer/src/libslic3r/Arachne/SkeletalTrapezoidationGraph.cpp

//Copyright (c) 2020 Ultimaker B.V.
//CuraEngine is released under the terms of the AGPLv3 or higher.

#include "SkeletalTrapezoidationGraph.hpp"

#include <ankerl/unordered_dense.h>
#include <boost/log/trivial.hpp>
#include <algorithm>
#include <cstdint>
#include <iostream>
#include <cassert>
#include <cinttypes>
#include <optional>
#include <utility>

#include "../Line.hpp"
#include "libslic3r/Arachne/utils/HalfEdge.hpp"
#include "libslic3r/libslic3r.h"
#include "libslic3r/Arachne/utils/HalfEdgeNode.hpp"
#include "libslic3r/Arachne/SkeletalTrapezoidationEdge.hpp"
#include "libslic3r/Arachne/SkeletalTrapezoidationJoint.hpp"
#include "libslic3r/Point.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)
{
    ankerl::unordered_dense::map<edge_t*, Edges::iterator> edge_locator;
    ankerl::unordered_dense::map<node_t*, Nodes::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, Edges::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, const Point &start_source_point, const Point &end_source_point) {
    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);
}

}