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Fix missing overhang layers with supported counterbore bridging #677

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Merged
zackaree-shen merged 2 commits into from
Aug 20, 2026
Merged

Fix missing overhang layers with supported counterbore bridging #677

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6f6cf5e
fix: counterbore bridge - keep model surface when support enabled (fi…
mwz-iot Aug 7, 2026
8224a35
fix: counterbore bridge - pre-shrink fill area to avoid perimeter ove…
mwz-iot Aug 7, 2026
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51 changes: 34 additions & 17 deletions src/libslic3r/PerimeterGenerator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1840,7 +1840,10 @@ void PerimeterGenerator::process_no_bridge(Surfaces& all_surfaces, coord_t perim
ExPolygons bridges_temp = offset2_ex(intersection_ex(last, diff_ex(unsupported_filtered, unbridgeable), ApplySafetyOffset::Yes), -ext_perimeter_width / 4, ext_perimeter_width / 4);
//remove the overhangs section from the surface polygons
ExPolygons reference = last;
last = diff_ex(last, unsupported_filtered);
// When support is enabled, do not remove the bridge area from the model surface,
// so that perimeters and overhang walls can still be generated for the supported overhang.
if (!this->object_config->enable_support.value)
last = diff_ex(last, unsupported_filtered);
//ExPolygons no_bridge = diff_ex(offset_ex(unbridgeable, ext_perimeter_width * 3 / 2), last);
//bridges_temp = diff_ex(bridges_temp, no_bridge);
coordf_t offset_to_do = bridged_infill_margin;
Expand Down Expand Up @@ -1881,22 +1884,36 @@ void PerimeterGenerator::process_no_bridge(Surfaces& all_surfaces, coord_t perim

if (!unsupported_filtered.empty()) {

//add this directly to the infill list.
// this will avoid to throw wrong offsets into a good polygons
this->fill_surfaces->append(
unsupported_filtered,
stInternal);

// store the results
last = diff_ex(last, unsupported_filtered, ApplySafetyOffset::Yes);
//remove "thin air" polygons (note: it assumes that all polygons below will be extruded)
for (int i = 0; i < last.size(); i++) {
if (intersection_ex(support, ExPolygons() = { last[i] }).empty()) {
this->fill_surfaces->append(
ExPolygons() = { last[i] },
stInternal);
last.erase(last.begin() + i);
i--;
if (!this->object_config->enable_support.value) {
// Support is disabled: remove the bridge area from the model surface
// to prevent unsupported perimeters, and add the full area to fill_surfaces
// to ensure the gap is still filled.
this->fill_surfaces->append(
unsupported_filtered,
stInternal);
last = diff_ex(last, unsupported_filtered, ApplySafetyOffset::Yes);
//remove "thin air" polygons (note: it assumes that all polygons below will be extruded)
for (int i = 0; i < last.size(); i++) {
if (intersection_ex(support, ExPolygons() = { last[i] }).empty()) {
this->fill_surfaces->append(
ExPolygons() = { last[i] },
stInternal);
last.erase(last.begin() + i);
i--;
}
}
} else {
// Support is enabled: keep the model surface intact so that perimeters
// and overhang walls are generated normally. Shrink the bridge fill area
// inward by the perimeter zone width before appending, to avoid overlap
// with the perimeter walls.
int wall_loops = std::max(1, this->config->wall_loops.value);
coord_t perimeter_zone = ext_perimeter_width / 2
+ perimeter_spacing * (wall_loops - 1)
+ perimeter_spacing / 2;
ExPolygons fill_safe = offset_ex(unsupported_filtered, -perimeter_zone);
if (!fill_safe.empty()) {
this->fill_surfaces->append(fill_safe, stInternal);
}
}
}
Expand Down