Collaboration diagram for Slic3r::LoopInterfaceProcessor:

Public Member Functions
	LoopInterfaceProcessor (coordf_t circle_r)
void	generate (SupportGeneratorLayerExtruded &top_contact_layer, const Flow &interface_flow_src) const

Public Attributes
int	n_contact_loops
coordf_t	circle_radius
coordf_t	circle_distance
Polygon	circle

Detailed Description

Constructor & Destructor Documentation

◆ LoopInterfaceProcessor()

Slic3r::LoopInterfaceProcessor::LoopInterfaceProcessor ( coordf_t circle_r )

inline

                                              :
        n_contact_loops(0),
        circle_radius(circle_r),
        circle_distance(circle_r * 3.)
    {
        // Shape of the top contact area.
        circle.points.reserve(6);
        for (size_t i = 0; i < 6; ++ i) {
            double angle = double(i) * M_PI / 3.;
            circle.points.push_back(Point(circle_radius * cos(angle), circle_radius * sin(angle)));
        }
    }

References Slic3r::angle(), circle, circle_distance, circle_radius, M_PI, and n_contact_loops.

Here is the call graph for this function:

Member Function Documentation

◆ generate()

void Slic3r::LoopInterfaceProcessor::generate	(	SupportGeneratorLayerExtruded &	top_contact_layer,
		const Flow &	interface_flow_src ) const

{
    if (n_contact_loops == 0 || top_contact_layer.empty())
        return;
 
    Flow flow = interface_flow_src.with_height(top_contact_layer.layer->height);
 
    Polygons overhang_polygons;
    if (top_contact_layer.layer->overhang_polygons != nullptr)
        overhang_polygons = std::move(*top_contact_layer.layer->overhang_polygons);
 
    // Generate the outermost loop.
    // Find centerline of the external loop (or any other kind of extrusions should the loop be skipped)
    ExPolygons top_contact_expolygons = offset_ex(union_ex(top_contact_layer.layer->polygons), - 0.5f * flow.scaled_width());
 
    // Grid size and bit shifts for quick and exact to/from grid coordinates manipulation.
    coord_t circle_grid_resolution = 1;
    coord_t circle_grid_powerof2 = 0;
    {
        // epsilon to account for rounding errors
        coord_t circle_grid_resolution_non_powerof2 = coord_t(2. * circle_distance + 3.);
        while (circle_grid_resolution < circle_grid_resolution_non_powerof2) {
            circle_grid_resolution <<= 1;
            ++ circle_grid_powerof2;
        }
    }
 
    struct PointAccessor {
        const Point* operator()(const Point &pt) const { return &pt; }
    };
    typedef ClosestPointInRadiusLookup<Point, PointAccessor> ClosestPointLookupType;
 
    Polygons loops0;
    {
        // find centerline of the external loop of the contours
        // Only consider the loops facing the overhang.
        Polygons external_loops;
        // Holes in the external loops.
        Polygons circles;
        Polygons overhang_with_margin = offset(union_ex(overhang_polygons), 0.5f * flow.scaled_width());
        for (ExPolygons::iterator it_contact_expoly = top_contact_expolygons.begin(); it_contact_expoly != top_contact_expolygons.end(); ++ it_contact_expoly) {
            // Store the circle centers placed for an expolygon into a regular grid, hashed by the circle centers.
            ClosestPointLookupType circle_centers_lookup(coord_t(circle_distance - SCALED_EPSILON));
            Points circle_centers;
            Point  center_last;
            // For each contour of the expolygon, start with the outer contour, continue with the holes.
            for (size_t i_contour = 0; i_contour <= it_contact_expoly->holes.size(); ++ i_contour) {
                Polygon     &contour = (i_contour == 0) ? it_contact_expoly->contour : it_contact_expoly->holes[i_contour - 1];
                const Point *seg_current_pt = nullptr;
                coordf_t     seg_current_t  = 0.;
                if (! intersection_pl(contour.split_at_first_point(), overhang_with_margin).empty()) {
                    // The contour is below the overhang at least to some extent.
                    //FIXME ideally one would place the circles below the overhang only.
                    // Walk around the contour and place circles so their centers are not closer than circle_distance from each other.
                    if (circle_centers.empty()) {
                        // Place the first circle.
                        seg_current_pt = &contour.points.front();
                        seg_current_t  = 0.;
                        center_last    = *seg_current_pt;
                        circle_centers_lookup.insert(center_last);
                        circle_centers.push_back(center_last);
                    }
                    for (Points::const_iterator it = contour.points.begin() + 1; it != contour.points.end(); ++it) {
                        // Is it possible to place a circle on this segment? Is it not too close to any of the circles already placed on this contour?
                        const Point &p1 = *(it-1);
                        const Point &p2 = *it;
                        // Intersection of a ray (p1, p2) with a circle placed at center_last, with radius of circle_distance.
                        const Vec2d v_seg(coordf_t(p2(0)) - coordf_t(p1(0)), coordf_t(p2(1)) - coordf_t(p1(1)));
                        const Vec2d v_cntr(coordf_t(p1(0) - center_last(0)), coordf_t(p1(1) - center_last(1)));
                        coordf_t a = v_seg.squaredNorm();
                        coordf_t b = 2. * v_seg.dot(v_cntr);
                        coordf_t c = v_cntr.squaredNorm() - circle_distance * circle_distance;
                        coordf_t disc = b * b - 4. * a * c;
                        if (disc > 0.) {
                            // The circle intersects a ray. Avoid the parts of the segment inside the circle.
                            coordf_t t1 = (-b - sqrt(disc)) / (2. * a);
                            coordf_t t2 = (-b + sqrt(disc)) / (2. * a);
                            coordf_t t0 = (seg_current_pt == &p1) ? seg_current_t : 0.;
                            // Take the lowest t in <t0, 1.>, excluding <t1, t2>.
                            coordf_t t;
                            if (t0 <= t1)
                                t = t0;
                            else if (t2 <= 1.)
                                t = t2;
                            else {
                                // Try the following segment.
                                seg_current_pt = nullptr;
                                continue;
                            }
                            seg_current_pt = &p1;
                            seg_current_t  = t;
                            center_last    = Point(p1(0) + coord_t(v_seg(0) * t), p1(1) + coord_t(v_seg(1) * t));
                            // It has been verified that the new point is far enough from center_last.
                            // Ensure, that it is far enough from all the centers.
                            std::pair<const Point*, coordf_t> circle_closest = circle_centers_lookup.find(center_last);
                            if (circle_closest.first != nullptr) {
                                -- it;
                                continue;
                            }
                        } else {
                            // All of the segment is outside the circle. Take the first point.
                            seg_current_pt = &p1;
                            seg_current_t  = 0.;
                            center_last    = p1;
                        }
                        // Place the first circle.
                        circle_centers_lookup.insert(center_last);
                        circle_centers.push_back(center_last);
                    }
                    external_loops.push_back(std::move(contour));
                    for (const Point &center : circle_centers) {
                        circles.push_back(circle);
                        circles.back().translate(center);
                    }
                }
            }
        }
        // Apply a pattern to the external loops.
        loops0 = diff(external_loops, circles);
    }
 
    Polylines loop_lines;
    {
        // make more loops
        Polygons loop_polygons = loops0;
        for (int i = 1; i < n_contact_loops; ++ i)
            polygons_append(loop_polygons,
                opening(
                    loops0,
                    i * flow.scaled_spacing() + 0.5f * flow.scaled_spacing(),
                    0.5f * flow.scaled_spacing()));
        // Clip such loops to the side oriented towards the object.
        // Collect split points, so they will be recognized after the clipping.
        // At the split points the clipped pieces will be stitched back together.
        loop_lines.reserve(loop_polygons.size());
        std::unordered_map<Point, int, PointHash> map_split_points;
        for (Polygons::const_iterator it = loop_polygons.begin(); it != loop_polygons.end(); ++ it) {
            assert(map_split_points.find(it->first_point()) == map_split_points.end());
            map_split_points[it->first_point()] = -1;
            loop_lines.push_back(it->split_at_first_point());
        }
        loop_lines = intersection_pl(loop_lines, expand(overhang_polygons, scale_(SUPPORT_MATERIAL_MARGIN)));
        // Because a closed loop has been split to a line, loop_lines may contain continuous segments split to 2 pieces.
        // Try to connect them.
        for (int i_line = 0; i_line < int(loop_lines.size()); ++ i_line) {
            Polyline &polyline = loop_lines[i_line];
            auto it = map_split_points.find(polyline.first_point());
            if (it != map_split_points.end()) {
                // This is a stitching point.
                // If this assert triggers, multiple source polygons likely intersected at this point.
                assert(it->second != -2);
                if (it->second < 0) {
                    // First occurence.
                    it->second = i_line;
                } else {
                    // Second occurence. Join the lines.
                    Polyline &polyline_1st = loop_lines[it->second];
                    assert(polyline_1st.first_point() == it->first || polyline_1st.last_point() == it->first);
                    if (polyline_1st.first_point() == it->first)
                        polyline_1st.reverse();
                    polyline_1st.append(std::move(polyline));
                    it->second = -2;
                }
                continue;
            }
            it = map_split_points.find(polyline.last_point());
            if (it != map_split_points.end()) {
                // This is a stitching point.
                // If this assert triggers, multiple source polygons likely intersected at this point.
                assert(it->second != -2);
                if (it->second < 0) {
                    // First occurence.
                    it->second = i_line;
                } else {
                    // Second occurence. Join the lines.
                    Polyline &polyline_1st = loop_lines[it->second];
                    assert(polyline_1st.first_point() == it->first || polyline_1st.last_point() == it->first);
                    if (polyline_1st.first_point() == it->first)
                        polyline_1st.reverse();
                    polyline.reverse();
                    polyline_1st.append(std::move(polyline));
                    it->second = -2;
                }
            }
        }
        // Remove empty lines.
        remove_degenerate(loop_lines);
    }
 
    // add the contact infill area to the interface area
    // note that growing loops by $circle_radius ensures no tiny
    // extrusions are left inside the circles; however it creates
    // a very large gap between loops and contact_infill_polygons, so maybe another
    // solution should be found to achieve both goals
    // Store the trimmed polygons into a separate polygon set, so the original infill area remains intact for
    // "modulate by layer thickness".
    top_contact_layer.set_polygons_to_extrude(diff(top_contact_layer.layer->polygons, offset(loop_lines, float(circle_radius * 1.1))));
 
    // Transform loops into ExtrusionPath objects.
    extrusion_entities_append_paths(
        top_contact_layer.extrusions,
        std::move(loop_lines),
        ExtrusionRole::erSupportMaterialInterface, flow.mm3_per_mm(), flow.width(), flow.height());
}