SuperSlicer/src/libslic3r/Fill/FillHoneycomb.cpp

#include "../ClipperUtils.hpp"
#include "../ShortestPath.hpp"
#include "../Surface.hpp"

#include "FillHoneycomb.hpp"

namespace Slic3r {

FillHoneycomb::Cache FillHoneycomb::cache{};

void FillHoneycomb::_fill_surface_single(
    const FillParams                &params, 
    unsigned int                     thickness_layers,
    const std::pair<float, Point>   &direction, 
    ExPolygon                        expolygon,
    Polylines                       &polylines_out) const
{
    double my_spacing = this->get_spacing();
    if(params.max_sparse_infill_spacing > 0)
        my_spacing = params.max_sparse_infill_spacing;
    // cache hexagons math
    CacheID cache_id(params.density, my_spacing);
    Cache::iterator it_m = FillHoneycomb::cache.find(cache_id);
    if (it_m == FillHoneycomb::cache.end()) {
        it_m = FillHoneycomb::cache.insert(it_m, std::pair<CacheID, CacheData>(cache_id, CacheData()));
        CacheData &m = it_m->second;
        coord_t min_spacing = scale_t(my_spacing);
        m.distance          = coord_t(double(min_spacing) / params.density);
        m.hex_side          = coord_t(double(m.distance) / (sqrt(3)/2));
        m.hex_width = m.distance * 2; // $m->{hex_width} == $m->{hex_side} * sqrt(3);
        coord_t hex_height = m.hex_side * 2;
        m.pattern_height = hex_height + m.hex_side;
        m.y_short           = coord_t(double(m.distance) * sqrt(3)/3);
        m.x_offset = min_spacing / 2;
        m.y_offset          = coord_t(double(m.x_offset) * sqrt(3)/3);
        m.hex_center = Point(m.hex_width/2, m.hex_side);
    }
    CacheData &m = it_m->second;

    Polylines all_polylines;
    {
        // adjust actual bounding box to the nearest multiple of our hex pattern
        // and align it so that it matches across layers
        
        BoundingBox bounding_box = expolygon.contour.bounding_box();
        {
            // rotate bounding box according to infill direction
            Polygon bb_polygon = bounding_box.polygon();
            bb_polygon.rotate(direction.first, m.hex_center);
            bounding_box = bb_polygon.bounding_box();
            
            // extend bounding box so that our pattern will be aligned with other layers
            // $bounding_box->[X1] and [Y1] represent the displacement between new bounding box offset and old one
            // The infill is not aligned to the object bounding box, but to a world coordinate system. Supposedly good enough.
            bounding_box.merge(align_to_grid(bounding_box.min, Point(m.hex_width, m.pattern_height)));
        }

        coord_t x = bounding_box.min(0);
        while (x <= bounding_box.max(0)) {
            Polyline p;
            coord_t ax[2] = { x + m.x_offset, x + m.distance - m.x_offset };
            for (size_t i = 0; i < 2; ++ i) {
                std::reverse(p.points.begin(), p.points.end()); // turn first half upside down
                for (coord_t y = bounding_box.min(1); y <= bounding_box.max(1); y += m.y_short + m.hex_side + m.y_short + m.hex_side) {
                    p.points.push_back(Point(ax[1], y + m.y_offset));
                    p.points.push_back(Point(ax[0], y + m.y_short - m.y_offset));
                    p.points.push_back(Point(ax[0], y + m.y_short + m.hex_side + m.y_offset));
                    p.points.push_back(Point(ax[1], y + m.y_short + m.hex_side + m.y_short - m.y_offset));
                    p.points.push_back(Point(ax[1], y + m.y_short + m.hex_side + m.y_short + m.hex_side + m.y_offset));
                }
                ax[0] = ax[0] + m.distance;
                ax[1] = ax[1] + m.distance;
                std::swap(ax[0], ax[1]); // draw symmetrical pattern
                x += m.distance;
            }
            p.rotate(-direction.first, m.hex_center);
            all_polylines.push_back(p);
        }
    }
    
    all_polylines = intersection_pl(std::move(all_polylines), expolygon);
    if (params.connection == icNotConnected || all_polylines.size() <= 1)
        append(polylines_out, chain_polylines(std::move(all_polylines)));
    else
        connect_infill(std::move(all_polylines), expolygon, polylines_out, scale_t(this->get_spacing()), params);
}

} // namespace Slic3r