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Only reverse order if the loops have steep overhang
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@Noisyfox
Noisyfox committed Oct 15, 2023
1 parent 2f568b4 commit 50b6027
Showing 1 changed file with 112 additions and 19 deletions.
131 changes: 112 additions & 19 deletions src/libslic3r/PerimeterGenerator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,10 @@ static const double narrow_loop_length_threshold = 10;
//we think it's small detail area and will generate smaller line width for it
static constexpr double SMALLER_EXT_INSET_OVERLAP_TOLERANCE = 0.22;

// Overhang width greater than this will be consider as steep overhang
// This is a percentage of the extrusion width
static constexpr double overhang_steep_width = 0.5; // TODO: make this configurable

namespace Slic3r {

// Hierarchy of perimeters.
Expand Down Expand Up @@ -216,12 +220,48 @@ static void lowpass_filter_by_paths_overhang_degree(ExtrusionPaths& paths) {
}
}

static ExtrusionEntityCollection traverse_loops(const PerimeterGenerator &perimeter_generator, const PerimeterGeneratorLoops &loops, ThickPolylines &thin_walls)
template<class _T>
static bool detect_steep_overhang(bool is_contour,
const BoundingBox &extrusion_bboxs,
double extrusion_width,
const _T extrusion,
const ExPolygons *lower_slices,
bool &steep_overhang_contour,
bool &steep_overhang_hole)
{
Polygons lower_slcier_chopped = ClipperUtils::clip_clipper_polygons_with_subject_bbox(*lower_slices, extrusion_bboxs, true);

// All we need to check is whether we have lines outside `overhang_steep_width`
double off = (overhang_steep_width - 0.5) * extrusion_width;

auto limiton_polygons = offset(lower_slcier_chopped, float(scale_(off)));

auto remain_polylines = diff_pl(extrusion, limiton_polygons);
if (!remain_polylines.empty()) {
if (is_contour) {
steep_overhang_contour = true;
} else {
steep_overhang_hole = true;
}

return true;
}

return false;
}

static ExtrusionEntityCollection traverse_loops(const PerimeterGenerator &perimeter_generator, const PerimeterGeneratorLoops &loops, ThickPolylines &thin_walls,
bool &steep_overhang_contour, bool &steep_overhang_hole)
{
// loops is an arrayref of ::Loop objects
// turn each one into an ExtrusionLoop object
ExtrusionEntityCollection coll;
Polygon fuzzified;

// Detect steep overhangs
bool overhangs_reverse = perimeter_generator.layer_id % 2 == 1 // Only calculate overhang degree on odd layers
&& perimeter_generator.config->fuzzy_skin == FuzzySkinType::None; // and not fuzzy skin

for (const PerimeterGeneratorLoop &loop : loops) {
bool is_external = loop.is_external();
bool is_small_width = loop.is_smaller_width_perimeter;
Expand Down Expand Up @@ -275,6 +315,14 @@ static ExtrusionEntityCollection traverse_loops(const PerimeterGenerator &perime
// prepare grown lower layer slices for overhang detection
BoundingBox bbox(polygon.points);
bbox.offset(SCALED_EPSILON);

// Detect steep overhang
// Skip the check if we already found steep overhangs
bool found_steep_overhang = (loop.is_contour && steep_overhang_contour) || (!loop.is_contour && steep_overhang_hole);
if (overhangs_reverse && !found_steep_overhang) {
detect_steep_overhang(loop.is_contour, bbox, extrusion_width, Polygons{polygon}, perimeter_generator.lower_slices,
steep_overhang_contour, steep_overhang_hole);
}

Polylines remain_polines;

Expand Down Expand Up @@ -375,15 +423,12 @@ static ExtrusionEntityCollection traverse_loops(const PerimeterGenerator &perime
} else {
const PerimeterGeneratorLoop &loop = loops[idx.first];
assert(thin_walls.empty());
ExtrusionEntityCollection children = traverse_loops(perimeter_generator, loop.children, thin_walls);
ExtrusionEntityCollection children = traverse_loops(perimeter_generator, loop.children, thin_walls, steep_overhang_contour, steep_overhang_hole);
out.entities.reserve(out.entities.size() + children.entities.size() + 1);
ExtrusionLoop *eloop = static_cast<ExtrusionLoop*>(coll.entities[idx.first]);
coll.entities[idx.first] = nullptr;
if (perimeter_generator.layer_id % 2 == 1) {
eloop->make_clockwise();
} else {
eloop->make_counter_clockwise();
}

eloop->make_counter_clockwise();
if (loop.is_contour) {
out.append(std::move(children.entities));
out.entities.emplace_back(eloop);
Expand Down Expand Up @@ -567,8 +612,13 @@ static void smooth_overhang_level(ExtrusionPaths &paths)
}
}

static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& perimeter_generator, std::vector<PerimeterGeneratorArachneExtrusion>& pg_extrusions)
static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& perimeter_generator, std::vector<PerimeterGeneratorArachneExtrusion>& pg_extrusions,
bool &steep_overhang_contour, bool &steep_overhang_hole)
{
// Detect steep overhangs
bool overhangs_reverse = perimeter_generator.layer_id % 2 == 1 // Only calculate overhang degree on odd layers
&& perimeter_generator.config->fuzzy_skin == FuzzySkinType::None; // and not fuzzy skin

ExtrusionEntityCollection extrusion_coll;
for (PerimeterGeneratorArachneExtrusion& pg_extrusion : pg_extrusions) {
Arachne::ExtrusionLine* extrusion = pg_extrusion.extrusion;
Expand Down Expand Up @@ -614,6 +664,33 @@ static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& p
// get non-overhang paths by intersecting this loop with the grown lower slices
extrusion_paths_append(temp_paths, clip_extrusion(extrusion_path, lower_slices_paths, ClipperLib_Z::ctIntersection), role,
is_external ? perimeter_generator.ext_perimeter_flow : perimeter_generator.perimeter_flow);

// Detect steep overhang
// Skip the check if we already found steep overhangs
bool found_steep_overhang = (pg_extrusion.is_contour && steep_overhang_contour) || (!pg_extrusion.is_contour && steep_overhang_hole);
if (overhangs_reverse && !found_steep_overhang) {
std::map<double, ExtrusionPaths> recognization_paths;
for (const ExtrusionPath &path : temp_paths) {
if (recognization_paths.count(path.width))
recognization_paths[path.width].emplace_back(std::move(path));
else
recognization_paths.insert(std::pair<double, ExtrusionPaths>(path.width, {std::move(path)}));
}
for (const auto &it : recognization_paths) {
Polylines be_clipped;

for (const ExtrusionPath &p : it.second) {
be_clipped.emplace_back(std::move(p.polyline));
}

BoundingBox extrusion_bboxs = get_extents(be_clipped);

if (detect_steep_overhang(pg_extrusion.is_contour, extrusion_bboxs, it.first, be_clipped, perimeter_generator.lower_slices,
steep_overhang_contour, steep_overhang_hole)) {
break;
}
}
}

if (perimeter_generator.config->overhang_speed_classic && perimeter_generator.config->enable_overhang_speed && perimeter_generator.config->fuzzy_skin == FuzzySkinType::None) {

Expand Down Expand Up @@ -723,13 +800,7 @@ static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& p
if (!paths.empty()) {
if (extrusion->is_closed) {
ExtrusionLoop extrusion_loop(std::move(paths), pg_extrusion.is_contour ? elrDefault : elrHole);
// Restore the orientation of the extrusion loop.
if (perimeter_generator.layer_id % 2 == 1) {
extrusion_loop.make_clockwise();
} else {
extrusion_loop.make_counter_clockwise();
}

extrusion_loop.make_counter_clockwise();
for (auto it = std::next(extrusion_loop.paths.begin()); it != extrusion_loop.paths.end(); ++it) {
assert(it->polyline.points.size() >= 2);
assert(std::prev(it)->polyline.last_point() == it->polyline.first_point());
Expand Down Expand Up @@ -1298,6 +1369,23 @@ void PerimeterGenerator::apply_extra_perimeters(ExPolygons &infill_area)
}
}

// Reorient loop direction
static void reorient_perimeters(ExtrusionEntityCollection &entities, bool steep_overhang_contour, bool steep_overhang_hole)
{
if (steep_overhang_hole || steep_overhang_contour) {
for (auto entity : entities) {
if (entity->is_loop()) {
ExtrusionLoop *eloop = static_cast<ExtrusionLoop *>(entity);
// Only reverse when needed
bool need_reverse = ((eloop->loop_role() & elrHole) == elrHole) ? steep_overhang_hole : steep_overhang_contour;
if (need_reverse) {
eloop->make_clockwise();
}
}
}
}
}

void PerimeterGenerator::process_classic()
{
// other perimeters
Expand Down Expand Up @@ -1585,7 +1673,10 @@ void PerimeterGenerator::process_classic()
}
}
// at this point, all loops should be in contours[0]
ExtrusionEntityCollection entities = traverse_loops(*this, contours.front(), thin_walls);
bool steep_overhang_contour = false;
bool steep_overhang_hole = false;
ExtrusionEntityCollection entities = traverse_loops(*this, contours.front(), thin_walls, steep_overhang_contour, steep_overhang_hole);
reorient_perimeters(entities, steep_overhang_contour, steep_overhang_hole);

// if brim will be printed, reverse the order of perimeters so that
// we continue inwards after having finished the brim
Expand Down Expand Up @@ -2125,11 +2216,13 @@ void PerimeterGenerator::process_arachne()
}
}
}



if (ExtrusionEntityCollection extrusion_coll = traverse_extrusions(*this, ordered_extrusions); !extrusion_coll.empty())
bool steep_overhang_contour = false;
bool steep_overhang_hole = false;
if (ExtrusionEntityCollection extrusion_coll = traverse_extrusions(*this, ordered_extrusions, steep_overhang_contour, steep_overhang_hole); !extrusion_coll.empty()) {
reorient_perimeters(extrusion_coll, steep_overhang_contour, steep_overhang_hole);
this->loops->append(extrusion_coll);
}

ExPolygons infill_contour = union_ex(wallToolPaths.getInnerContour());
const coord_t spacing = (perimeters.size() == 1) ? ext_perimeter_spacing2 : perimeter_spacing;
Expand Down

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