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minimize travel over already printed parts #15553

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2ed4efc
Add alternating print order and travel avoidance
mikecarper Aug 5, 2026
55cd95f
Use WRL for Windows COM helpers
mikecarper Aug 5, 2026
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75 changes: 55 additions & 20 deletions src/libslic3r/GCode.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2668,7 +2668,8 @@ LayerResult GCodeGenerator::process_layer(
}

// Initialize avoid crossing perimeters before a layer change.
if (!instances_to_print.empty() && print.config().avoid_crossing_perimeters) {
if (!instances_to_print.empty() &&
(print.config().avoid_crossing_perimeters || print.config().avoid_crossing_printed_areas)) {
const InstanceToPrint instance_to_print{instances_to_print.front()};
this->m_avoid_crossing_perimeters.init_layer(
*layers[instance_to_print.object_layer_to_print_id].layer());
Expand Down Expand Up @@ -2776,7 +2777,8 @@ LayerResult GCodeGenerator::process_layer(
gcode += ProcessLayer::emit_custom_gcode_per_print_z(*this, *layer_tools.custom_gcode, m_writer.extruder()->id(), first_extruder_id, print.config());
}

if (!extruder_extrusions.skirt.empty() || !extruder_extrusions.brim.empty()) {
if ((!extruder_extrusions.skirt_last && !extruder_extrusions.skirt.empty()) ||
!extruder_extrusions.brim.empty()) {
gcode += m_label_objects.maybe_stop_instance();
this->m_label_objects.update(nullptr);
}
Expand Down Expand Up @@ -2805,7 +2807,10 @@ LayerResult GCodeGenerator::process_layer(
this->set_origin({0, 0});
}

if (!extruder_extrusions.skirt.empty()) {
const auto extrude_layer_skirt = [&]() {
if (extruder_extrusions.skirt.empty())
return;

this->m_label_objects.update(nullptr);

m_avoid_crossing_perimeters.use_external_mp();
Expand All @@ -2821,9 +2826,13 @@ LayerResult GCodeGenerator::process_layer(
}
m_avoid_crossing_perimeters.use_external_mp(false);
// Allow a straight travel move to the first object point if this is the first layer (but don't in next layers).
if (first_layer && extruder_extrusions.skirt.front().first == 0)
if (first_layer && extruder_extrusions.skirt.front().first == 0 &&
!m_config.avoid_crossing_printed_areas)
m_avoid_crossing_perimeters.disable_once();
}
};

if (!extruder_extrusions.skirt_last)
extrude_layer_skirt();

if (!extruder_extrusions.brim.empty()) {
m_avoid_crossing_perimeters.use_external_mp();
Expand All @@ -2833,7 +2842,8 @@ LayerResult GCodeGenerator::process_layer(
}
m_avoid_crossing_perimeters.use_external_mp(false);
// Allow a straight travel move to the first object point.
m_avoid_crossing_perimeters.disable_once();
if (!m_config.avoid_crossing_printed_areas)
m_avoid_crossing_perimeters.disable_once();
}

m_label_objects.update(first_instance);
Expand Down Expand Up @@ -2882,9 +2892,20 @@ LayerResult GCodeGenerator::process_layer(
instance, layer_to_print, slices_extrusions
);
}

if (extruder_extrusions.skirt_last && !extruder_extrusions.skirt.empty()) {
this->set_origin(0.0, 0.0);
gcode += m_label_objects.maybe_stop_instance();
this->m_label_objects.update(nullptr);
extrude_layer_skirt();
}
this->set_origin(0.0, 0.0);
}

const bool fresh_travel_cooldown =
m_avoid_crossing_perimeters.consume_fresh_travel_cooldown();
if (!last_layer && print.config().avoid_crossing_printed_areas && fresh_travel_cooldown)
gcode += ";_FRESH_TRAVEL_COOLDOWN\n";

BOOST_LOG_TRIVIAL(trace) << "Exported layer " << layer.id() << " print_z " << print_z <<
log_memory_info();
Expand All @@ -2909,7 +2930,8 @@ void GCodeGenerator::initialize_instance(
const Point &offset = print_object.instances()[print_instance.instance_id].shift;
GCode::PrintObjectInstance next_instance = {&print_object, int(print_instance.instance_id)};

if (print.config().avoid_crossing_perimeters && !is_first) {
if ((print.config().avoid_crossing_perimeters || print.config().avoid_crossing_printed_areas) &&
!is_first) {
m_avoid_crossing_perimeters.init_layer(*m_layer);

// When starting a new object, use the external motion planner for the first travel move.
Expand Down Expand Up @@ -3142,6 +3164,24 @@ std::string GCodeGenerator::extrude_smooth_path(
m_wipe.set_path(std::move(reversed_smooth_path));
}

if (m_config.avoid_crossing_printed_areas) {
Polyline recent_path;
for (const GCode::SmoothPathElement &element : smooth_path) {
for (const Geometry::ArcWelder::Segment &segment : element.path) {
if (recent_path.empty() || recent_path.back() != segment.point)
recent_path.append(segment.point);
}
}
if (recent_path.size() >= 2) {
std::optional<bool> clockwise;
if (is_loop && recent_path.size() >= 3)
clockwise = Polygon(recent_path.points).is_clockwise();
recent_path.translate(Point::new_scale(m_origin.x(), m_origin.y()));
m_avoid_crossing_perimeters.register_recent_extrusion(
std::move(recent_path), clockwise);
}
}

return gcode;
}

Expand Down Expand Up @@ -3773,16 +3813,15 @@ Polyline GCodeGenerator::generate_travel_xy_path(
) {

const Point scaled_origin{scaled(this->origin())};
const bool avoid_crossing_perimeters = (
this->m_config.avoid_crossing_perimeters
&& !this->m_avoid_crossing_perimeters.disabled_once()
);
const bool perimeter_aware_travel =
(this->m_config.avoid_crossing_perimeters || this->m_config.avoid_crossing_printed_areas) &&
!this->m_avoid_crossing_perimeters.disabled_once();

Polyline xy_path{start_point, end_point};
if (m_config.avoid_crossing_curled_overhangs) {
if (avoid_crossing_perimeters) {
if (perimeter_aware_travel) {
BOOST_LOG_TRIVIAL(warning)
<< "Option >avoid crossing curled overhangs< is not compatible with avoid crossing perimeters and it will be ignored!";
<< "Option >avoid crossing curled overhangs< is not compatible with perimeter-aware travel planning and it will be ignored!";
} else {
xy_path = this->m_avoid_crossing_curled_overhangs.find_path(
start_point + scaled_origin,
Expand All @@ -3792,13 +3831,9 @@ Polyline GCodeGenerator::generate_travel_xy_path(
}
}


// if a retraction would be needed, try to use avoid_crossing_perimeters to plan a
// multi-hop travel path inside the configuration space
if (
needs_retraction
&& avoid_crossing_perimeters
) {
// Avoid crossing perimeters is only needed for retracting travels. Minimize travel over
// printed areas applies to every travel because even a non-retracting move may cross a surface.
if (perimeter_aware_travel && (needs_retraction || this->m_config.avoid_crossing_printed_areas)) {
xy_path = this->m_avoid_crossing_perimeters.travel_to(*this, end_point, &could_be_wipe_disabled);
}

Expand Down
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