feat(orient): auto-orient the largest overhang toward the cooling fan

New printer option fan_direction (undefine/left/right/both, default
undefine) declares which side the auxiliary part-cooling airflow comes
from. When set and the printer has an auxiliary fan, auto-orient adds a
yaw rotation so the dominant overhang area faces the airflow, and newly
added primitive shapes are pre-oriented the same way (except the Cube,
whose axis-aligned bounding box the pressure-advance pattern calibration
depends on).

- FanDirection enum + fan_direction printer option (Accessory group,
  enabled only with auxiliary_fan)
- orient engine: weighted overhang areas per candidate, yaw-direction
  search, vertical rotation applied on top of the primary orientation;
  the cooling weights are taken from the candidate actually chosen,
  including the flat-bottom tie-break
- orient_for_cooling() for primitive placement
- set fan_direction=left on H2C/H2D/H2D Pro/X1/X1E/P1S 0.4 profiles
  (X1C/H2S/P2S/X2D/Qidi X-Max 4 already carried the key, which now
  takes effect)

With fan_direction unset or no auxiliary fan the vertical rotation stays
identity and auto-orient results are unchanged; slicing and g-code are
never affected.

localization/i18n/OrcaSlicer.pot

@@ -18740,3 +18740,12 @@ msgstr ""
 
 msgid "Switch track at Filament Track Switch"
 msgstr ""
+
+msgid "Fan direction"
+msgstr ""
+
+msgid "Cooling fan direction of the printer"
+msgstr ""
+
+msgid "Both"
+msgstr ""

resources/profiles/BBL/machine/Bambu Lab H2C 0.4 nozzle.json

@@ -31,6 +31,7 @@
 		"1",
 		"6"
 	],
+	"fan_direction": "left",
 	"hotend_cooling_rate": [
 		"1.6",
 		"1.6",

resources/profiles/BBL/machine/Bambu Lab H2D 0.4 nozzle.json

@@ -24,6 +24,7 @@
 		"0x0,325x0,325x320,0x320",
 		"25x0,350x0,350x320,25x320"
 	],
+	"fan_direction": "left",
 	"hotend_heating_rate": [
 		"3.6",
 		"3.6",

resources/profiles/BBL/machine/Bambu Lab H2D Pro 0.4 nozzle.json

@@ -27,6 +27,7 @@
 		"0x0,325x0,325x320,0x320",
 		"25x0,350x0,350x320,25x320"
 	],
+	"fan_direction": "left",
 	"hotend_heating_rate": [
 		"3.6",
 		"3.6",

resources/profiles/BBL/machine/Bambu Lab P1S 0.4 nozzle.json

@@ -28,6 +28,7 @@
 	"extruder_variant_list": [
 		"Direct Drive Standard,Direct Drive High Flow"
 	],
+	"fan_direction": "left",
 	"long_retractions_when_cut": [
 		"0",
 		"0"

resources/profiles/BBL/machine/Bambu Lab X1 0.4 nozzle.json

@@ -34,6 +34,7 @@
 	"extruder_variant_list": [
 		"Direct Drive Standard,Direct Drive High Flow"
 	],
+	"fan_direction": "left",
 	"long_retractions_when_cut": [
 		"0",
 		"0"

resources/profiles/BBL/machine/Bambu Lab X1E 0.4 nozzle.json

@@ -28,6 +28,7 @@
 	"extruder_variant_list": [
 		"Direct Drive Standard,Direct Drive High Flow"
 	],
+	"fan_direction": "left",
 	"long_retractions_when_cut": [
 		"0",
 		"0"

src/libslic3r/Orient.cpp

@@ -27,19 +27,20 @@ namespace Slic3r {
 namespace orientation {
 
     struct CostItems {
-        float overhang;
+        float overhang = 0;
-        float bottom;
+        float bottom = 0;
-        float bottom_hull;
+        float bottom_hull = 0;
-        float contour;
+        float contour = 0;
-        float area_laf;  // area_of_low_angle_faces
+        float area_laf = 0;  // area_of_low_angle_faces
-        float area_projected; // area of projected 2D profile
+        float area_projected = 0; // area of projected 2D profile
-        float volume;
+        float volume = 0;
-        float area_total;  // total area of all faces
+        float area_total = 0;  // total area of all faces
-        float radius;    // radius of bounding box
+        float radius = 0;    // radius of bounding box
-        float height_to_bottom_hull_ratio;  // affects stability, the lower the better
+        float height_to_bottom_hull_ratio = 0;  // affects stability, the lower the better
-        float unprintability;
+        float unprintability = 0;
+        Eigen::VectorXf areas_cooling;
         CostItems(CostItems const & other) = default;
-        CostItems() { memset(this, 0, sizeof(*this)); }
+        CostItems() = default;
         static std::string field_names() {
             return "                                      overhang, bottom, bothull, contour, A_laf, A_prj, unprintability";
         }
@@ -68,10 +69,11 @@ public:
     Eigen::VectorXf z_max, z_max_hull;  // max of projected z
     Eigen::VectorXf z_median;  // median of projected z
     Eigen::VectorXf z_mean;  // mean of projected z
+    Eigen::VectorXf areas_cooling;  // weighted areas for cool direction
     std::vector<Vec3f> face_normals;
     std::vector<Vec3f> face_normals_hull;
     OrientParams params;
-
+    bool has_cooling_fan = false;
 
     std::vector< Vec3f> orientations;  // Vec3f == stl_normal
     std::function<void(unsigned)> progressind = { };  // default empty indicator function
@@ -85,6 +87,7 @@ public:
         orient_mesh = orient_mesh_;
         mesh = &orient_mesh->mesh;
         params = params_;
+        has_cooling_fan = orient_mesh->has_cooling_fan;
         progressind = progressind_;
         params.ASCENT = cos(PI - orient_mesh->overhang_angle * PI / 180); // use per-object overhang angle
         
@@ -158,12 +161,14 @@ public:
         //To avoid flipping, we need to verify if there are orientations with same unprintability.
         Vec3f n1 = {0, 0, 1};
         auto best_orientation = results_vector[0].first;
+        size_t best_index = 0;
 
         for (int i = 1; i< results_vector.size()-1; i++) {
             if (abs(results_vector[i].second.unprintability - results_vector[0].second.unprintability) < EPSILON && abs(results_vector[0].first.dot(n1)-1) > EPSILON) {
-                if (abs(results_vector[i].first.dot(n1)-1) < EPSILON*EPSILON) { 
+                if (abs(results_vector[i].first.dot(n1)-1) < EPSILON*EPSILON) {
                     best_orientation = n1;
-                    break; 
+                    best_index = i;
+                    break;
                 }
             }
             else {
@@ -172,6 +177,9 @@ public:
 
         }
 
+        // cooling weights are per-orientation, so take them from the orientation actually chosen
+        areas_cooling = results_vector[best_index].second.areas_cooling;
+
         BOOST_LOG_TRIVIAL(info) << std::fixed << std::setprecision(6) << "best:" << best_orientation.transpose() << ", costs:" << results_vector[0].second.field_values();
         std::cout << std::fixed << std::setprecision(6) << "best:" << best_orientation.transpose() << ", costs:" << results_vector[0].second.field_values() << std::endl;
 
@@ -441,6 +449,19 @@ public:
         Eigen::MatrixXf laf_areas = ((normal_projection_abs.array() < params.LAF_MAX) * (normal_projection_abs.array() > params.LAF_MIN) * (z_max.array() > total_min_z + params.FIRST_LAY_H)).select(areas, 0);
         costs.area_laf = laf_areas.sum();
 
+        if (has_cooling_fan)
+        {
+            // Angle range of overhang faces requiring cooling
+            float angle_thres_high = -0.6427f;
+            float angle_thres_low = -0.97f;
+            // compute the weighted overhang faces area
+            Eigen::VectorXf ones_f = Eigen::VectorXf::Ones(mesh->facets_count());
+            auto overhang_area_condition = (normal_projection.array() < angle_thres_high && normal_projection.array() > angle_thres_low).eval();
+            Eigen::VectorXf areas_ = (overhang_area_condition * !bottom_condition_2nd).select(areas, 0);
+            Eigen::VectorXf weighted_areas = areas_.cwiseProduct(ones_f - normal_projection);
+            costs.areas_cooling = weighted_areas;
+        }
+
         // height to bottom_hull_area ratio
         //float total_max_z = z_projected.maxCoeff();
         //costs.height_to_bottom_hull_ratio = SQ(total_max_z) / (costs.bottom_hull + 1e-7);
@@ -468,6 +489,67 @@ public:
 
         return cost;
     }
+
+    Vec3d find_cooling_direction2(Vec3d euler_angles, const Eigen::VectorXf& areas_in, TriangleMesh& mesh)
+    {
+        Vec3f machine_cool_dir = this->orient_mesh->cooling_direction.cast<float>();
+        const size_t num_faces = areas.rows();
+        Vec3f best_direction = { 0, 0, 0 };
+
+        // 1. Make a copy of input mesh, rotate and translate to the best orientation
+        TriangleMesh mesh_copy = TriangleMesh(mesh.its);
+        mesh_copy.rotate_x(euler_angles(0, 0));
+        mesh_copy.rotate_y(euler_angles(1, 0));
+        mesh_copy.rotate_z(euler_angles(2, 0));
+        auto bounding_box = mesh_copy.bounding_box();
+        Eigen::VectorXf translate_distance = bounding_box.min.array().cast<float>();
+        Vec3d mesh_center = mesh_copy.center();
+        mesh_copy.translate(-mesh_center(0), -mesh_center(1), -translate_distance(2));
+
+        // 2. sample cooling direction
+        const size_t sample_nums = 180;
+        std::vector<Vec3f> cool_dirs;
+        for (size_t i = 0; i < sample_nums; i++)
+        {
+            float angle_deg = i * (360.0 / sample_nums);
+            float angle_rad = angle_deg * (PI / 180.0);
+            cool_dirs.push_back(Vec3f{ std::cos(angle_rad), std::sin(angle_rad), 0});
+        }
+
+        // 3. accumulate the weighted projected overhang area, find the max weighted project area direction
+        std::vector<Vec3f> face_normals_copy = its_face_normals(mesh_copy.its);
+        float overhang_projected_max = 0.f;
+        float overhang_projected_origin = 0.f;
+        for (auto cool_dir : cool_dirs)
+        {
+            float overhang_projected_tmp = 0.f;
+            for (size_t i = 0; i < num_faces; i++)
+            {
+                float cool_dir_projection = face_normals_copy[i].dot(cool_dir);
+                if (areas_in[i] > 0 && cool_dir_projection > 0)
+                {
+                    overhang_projected_tmp += areas_in[i] * cool_dir_projection;
+                }
+            }
+            if (overhang_projected_tmp > overhang_projected_max)
+            {
+                overhang_projected_max = overhang_projected_tmp;
+                best_direction = cool_dir;
+            }
+            if (cool_dir.dot(machine_cool_dir) > 0.999)
+            {
+                overhang_projected_origin = overhang_projected_tmp;
+            }
+        }
+
+        // The symmetric model has similar overhang projection at all angles, so Z-axis rotation is unnecessary.
+        if (std::abs(overhang_projected_origin - overhang_projected_max) < 1.0f)
+        {
+            best_direction = machine_cool_dir;
+        }
+        BOOST_LOG_TRIVIAL(info) << "best cooling dir = " << best_direction.transpose() << "\n";
+        return best_direction.cast<double>();
+    }
 };
 
 void _orient(OrientMeshs& meshs_,
@@ -497,6 +579,13 @@ void _orient(OrientMeshs& meshs_,
                 mesh_.orientation = orienter.process();
                 Geometry::rotation_from_two_vectors(mesh_.orientation, { 0,0,1 }, mesh_.axis, mesh_.angle, &mesh_.rotation_matrix);
                 mesh_.euler_angles = Geometry::extract_euler_angles(mesh_.rotation_matrix);
+                // find cool direction
+                if (mesh_.has_cooling_fan)
+                {
+                    mesh_.orientation_vertical = orienter.find_cooling_direction2(mesh_.euler_angles, orienter.areas_cooling, mesh_.mesh);
+                    BOOST_LOG_TRIVIAL(info) << "cooling direction: " << mesh_.orientation_vertical.transpose() << "\n";
+                    Geometry::rotation_from_two_vectors(mesh_.orientation_vertical, mesh_.cooling_direction, mesh_.axis_vertical, mesh_.angle_vertical, &mesh_.rotation_matrix_vertical);
+                }
                 BOOST_LOG_TRIVIAL(debug) << "rotation_from_two_vectors: " << mesh_.orientation << "; " << mesh_.axis << "; " << mesh_.angle << "; euler: " << mesh_.euler_angles.transpose();
             }});
     }
@@ -539,6 +628,94 @@ void orient(ModelInstance* instance)
     instance->rotate(rotation_matrix);
 }
 
+void orient_for_cooling(TriangleMesh& mesh, const FanDirection& fan_dir)
+{
+    Vec3f best_direction{ 0, 0, 0 };
+    Vec3f machine_cool_dir{ 0, 0, 0 };
+
+    if (fan_dir == FanDirection::fdUndefine)
+    {
+        // no cooling fan, do not rotate along z axis
+        return;
+    }
+    else if (fan_dir == FanDirection::fdRight)
+    {
+        machine_cool_dir = { 1, 0, 0 };   // the cooling fan is on the right side.
+    }
+    else
+    {
+        // the cooling fan is on the left side or both side has cooling fans
+        machine_cool_dir = { -1, 0, 0 };
+    }
+
+    // 1. filter the overhang_areas
+    int nfaces = mesh.facets_count();
+    auto face_normals = its_face_normals(mesh.its);
+
+    Eigen::VectorXf normal_projection(nfaces, 1);
+    for (auto i = 0; i < nfaces; i++)
+    {
+        normal_projection(i) = face_normals[i].dot(Vec3f(0, 0, 1));
+    }
+    float angle_thres_high = -0.6427f;
+    float angle_thres_low = -0.97f;
+    // 2. compute the weighted overhang faces area
+    Eigen::VectorXf weighted_areas = Eigen::VectorXf::Zero(nfaces);
+    for (int i = 0; i < nfaces; i++)
+    {
+        if (normal_projection(i) < angle_thres_high && normal_projection(i) > angle_thres_low)
+        {
+            weighted_areas(i) = mesh.its.facet_area(i) * (1.0f - normal_projection(i));
+        }
+    }
+
+    const size_t sample_nums = 180;
+    std::vector<Vec3f> cool_dirs;
+    for (size_t i = 0; i < sample_nums; i++)
+    {
+        float angle_deg = i * (360.0 / sample_nums);
+        float angle_rad = angle_deg * (PI / 180.0);
+        cool_dirs.push_back(Vec3f{ std::cos(angle_rad), std::sin(angle_rad), 0 });
+    }
+
+    // 3. accumulate the weighted projected overhang area, find the max weighted project area direction
+    float overhang_projected_max = 0.f;
+    float overhang_projected_origin = 0.f;
+    for (auto cool_dir : cool_dirs)
+    {
+        float overhang_projected_tmp = 0.f;
+        for (size_t i = 0; i < nfaces; i++)
+        {
+            float cool_dir_projection = face_normals[i].dot(cool_dir);
+            if (weighted_areas[i] > 0 && cool_dir_projection > 0)
+            {
+                overhang_projected_tmp += weighted_areas[i] * cool_dir_projection;
+            }
+        }
+        if (overhang_projected_tmp > overhang_projected_max)
+        {
+            overhang_projected_max = overhang_projected_tmp;
+            best_direction = cool_dir;
+        }
+        if (cool_dir.dot(machine_cool_dir) > 0.999)
+        {
+            overhang_projected_origin = overhang_projected_tmp;
+        }
+    }
+
+    // The symmetric model has similar overhang projection at all angles, so Z-axis rotation is unnecessary.
+    if (std::abs(overhang_projected_origin - overhang_projected_max) < 1.0f)
+    {
+        return;
+    }
+
+    // rotate the mesh
+    Vec3d axis;
+    double angle;
+    Matrix3d rotation_matrix;
+    Geometry::rotation_from_two_vectors(best_direction.cast<double>(), machine_cool_dir.cast<double>(), axis, angle, &rotation_matrix);
+    mesh.rotate(angle, axis);
+}
 
 } // namespace arr
 } // namespace Slic3r

src/libslic3r/Orient.hpp

@@ -26,10 +26,18 @@ struct OrientMesh {
     TriangleMesh mesh;              /// The real mesh data
     double overhang_angle = 30;
     double angle{ 0 };
+    double angle_vertical{ 0 };
     Vec3d axis{ 0,0,1 };
+    Vec3d axis_vertical{ 0,0,1 };
     Vec3d orientation{ 0,0,1 };
-    Matrix3d rotation_matrix;
+    Vec3d orientation_vertical{ -1,0,0 };
-    Vec3d euler_angles;
+    Matrix3d rotation_matrix = Matrix3d::Identity();
+    Matrix3d rotation_matrix_vertical = Matrix3d::Identity();
+    Vec3d euler_angles = {0, 0, 0};
+    Vec3d euler_angles_vertical = {0, 0, 0};
+    Vec3d cooling_direction = {0, 0, 0};
+    bool has_cooling_fan{false};
+
     std::string name;
 
     /// Optional setter function which can store arbitrary data in its closure
@@ -154,6 +162,9 @@ void orient(ModelObject* obj);
 
 void orient(ModelInstance* instance);
 
+// rotate z axis for cooling
+void orient_for_cooling(TriangleMesh& mesh, const FanDirection& fan_dir);
+
 }} // namespace Slic3r::orientment
 
 #endif // MODELORIENT_HPP

src/libslic3r/Preset.cpp

@@ -1390,7 +1390,7 @@ static std::vector<std::string> s_Preset_printer_options {
     "default_print_profile", "inherits",
     "silent_mode",
     "scan_first_layer", "enable_power_loss_recovery", "wrapping_detection_layers", "wrapping_exclude_area", "machine_load_filament_time", "machine_unload_filament_time", "machine_tool_change_time", "time_cost", "machine_pause_gcode", "template_custom_gcode",
-    "nozzle_type", "nozzle_hrc","auxiliary_fan", "nozzle_volume","upward_compatible_machine", "z_hop_types", "travel_slope", "retract_lift_enforce","support_chamber_temp_control","support_air_filtration","cooling_filter_enabled","printer_structure","farthest_point_timelapse",
+    "nozzle_type", "nozzle_hrc","auxiliary_fan", "fan_direction", "nozzle_volume","upward_compatible_machine", "z_hop_types", "travel_slope", "retract_lift_enforce","support_chamber_temp_control","support_air_filtration","cooling_filter_enabled","printer_structure","farthest_point_timelapse",
     "best_object_pos", "head_wrap_detect_zone",
     "host_type", "print_host", "printhost_apikey", "flashforge_serial_number", "bbl_use_printhost", "printer_agent",
     "print_host_webui",

src/libslic3r/PrintConfig.cpp

@@ -512,6 +512,14 @@ static t_config_enum_values s_keys_map_NozzleType {
 };
 CONFIG_OPTION_ENUM_DEFINE_STATIC_MAPS(NozzleType)
 
+static t_config_enum_values s_keys_map_FanDirection {
+    { "undefine",       int(FanDirection::fdUndefine) },
+    { "left",           int(FanDirection::fdLeft) },
+    { "right",          int(FanDirection::fdRight) },
+    { "both",           int(FanDirection::fdBoth) }
+};
+CONFIG_OPTION_ENUM_DEFINE_STATIC_MAPS(FanDirection)
+
 static t_config_enum_values s_keys_map_PrinterStructure {
     {"undefine",        int(PrinterStructure::psUndefine)},
     {"corexy",          int(PrinterStructure::psCoreXY)},
@@ -3997,6 +4005,21 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(false));
 
+    def = this->add("fan_direction", coEnum);
+    def->label = L("Fan direction");
+    def->tooltip = L("Cooling fan direction of the printer");
+    def->enum_keys_map = &ConfigOptionEnum<FanDirection>::get_enum_values();
+    def->enum_values.push_back("undefine");
+    def->enum_values.push_back("left");
+    def->enum_values.push_back("right");
+    def->enum_values.push_back("both");
+    def->enum_labels.push_back(L("Undefined"));
+    def->enum_labels.push_back(L("Left"));
+    def->enum_labels.push_back(L("Right"));
+    def->enum_labels.push_back(L("Both"));
+    def->mode = comDevelop;
+    def->set_default_value(new ConfigOptionEnum<FanDirection>(fdUndefine));
+
     def = this->add("fan_speedup_time", coFloat);
 	// Label is set in Tab.cpp in the Line object.
     //def->label = L("Fan speed-up time");

src/libslic3r/PrintConfig.hpp

@@ -362,6 +362,13 @@ enum LayerSeq {
     flsCustomize
 };
 
+enum FanDirection {
+    fdUndefine = 0,
+    fdLeft,
+    fdRight,
+    fdBoth
+};
+
 static std::unordered_map<NozzleType, std::string>NozzleTypeEumnToStr = {
     {NozzleType::ntUndefine,        "undefine"},
     {NozzleType::ntHardenedSteel,   "hardened_steel"},
@@ -1494,6 +1501,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionEnumsGenericNullable,nozzle_type))
     ((ConfigOptionInt,                 nozzle_hrc))
     ((ConfigOptionBool,                auxiliary_fan))
+    ((ConfigOptionEnum<FanDirection>,  fan_direction))
     ((ConfigOptionBool,                support_air_filtration))
     ((ConfigOptionBool,                cooling_filter_enabled))
     ((ConfigOptionEnum<PrinterStructure>,printer_structure))

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -38,6 +38,7 @@
 
 #include "slic3r/Utils/FixModelByCgal.hpp"
 #include "libslic3r/Format/bbs_3mf.hpp"
+#include "libslic3r/Orient.hpp"
 #include "libslic3r/PrintConfig.hpp"
 
 #ifdef __WXMSW__
@@ -2560,6 +2561,15 @@ void ObjectList::load_shape_object(const std::string &type_name)
     // Create mesh
     BoundingBoxf3 bb;
     TriangleMesh mesh = create_mesh(type_name, bb);
+    // Rotate the largest overhang area toward the part cooling fan so new shapes start in a
+    // cooling friendly orientation. Skip the plain cube: the pressure advance pattern
+    // calibration reuses it as an axis-aligned anchor and scales it by its bounding box,
+    // so its orientation must stay fixed.
+    const Slic3r::DynamicPrintConfig& full_config = wxGetApp().preset_bundle->full_config();
+    if (type_name != "Cube" && full_config.has("fan_direction") && full_config.has("auxiliary_fan")) {
+        FanDirection config_dir = full_config.option<ConfigOptionEnum<FanDirection>>("fan_direction")->value;
+        orientation::orient_for_cooling(mesh, config_dir);
+    }
     // BBS: remove "Shape" prefix
     load_mesh_object(mesh, _(type_name));
     wxGetApp().mainframe->update_title();

src/slic3r/GUI/Jobs/OrientJob.cpp

@@ -229,15 +229,32 @@ orientation::OrientMesh OrientJob::get_orient_mesh(ModelInstance* instance)
     auto obj = instance->get_object();
     om.name = obj->name;
     om.mesh = obj->mesh(); // don't know the difference to obj->raw_mesh(). Both seem OK
+    const Slic3r::DynamicPrintConfig& config = wxGetApp().preset_bundle->full_config();
     if (obj->config.has("support_threshold_angle"))
         om.overhang_angle = obj->config.opt_int("support_threshold_angle");
     else {
-        const Slic3r::DynamicPrintConfig& config = wxGetApp().preset_bundle->full_config();
         om.overhang_angle = config.opt_int("support_threshold_angle");
     }
 
+    if (config.has("fan_direction") && config.has("auxiliary_fan")) {
+        FanDirection config_dir = config.option<ConfigOptionEnum<FanDirection>>("fan_direction")->value;
+        if (config_dir == FanDirection::fdUndefine || !config.opt_bool("auxiliary_fan")) {
+            // no part cooling airflow to face, keep the orientation around the z axis unchanged
+            om.cooling_direction = {0, 0, 0};
+        } else if (config_dir == FanDirection::fdRight) {
+            // the part cooling airflow comes from the right side
+            om.cooling_direction = {1, 0, 0};
+            om.has_cooling_fan = true;
+        } else {
+            // the part cooling airflow comes from the left side, or from both sides
+            om.cooling_direction = {-1, 0, 0};
+            om.has_cooling_fan = true;
+        }
+    }
+
     om.setter = [instance](const OrientMesh& p) {
         instance->rotate(p.rotation_matrix);
+        instance->rotate(p.rotation_matrix_vertical);
         instance->get_object()->invalidate_bounding_box();
         instance->get_object()->ensure_on_bed();
     };

src/slic3r/GUI/Tab.cpp

@@ -4956,6 +4956,7 @@ void TabPrinter::build_fff()
         optgroup->append_single_option_line("nozzle_type", "printer_basic_information_accessory#nozzle-type");
         optgroup->append_single_option_line("nozzle_hrc", "printer_basic_information_accessory#nozzle-hrc");
         optgroup->append_single_option_line("auxiliary_fan", "printer_basic_information_accessory#auxiliary-part-cooling-fan");
+        optgroup->append_single_option_line("fan_direction");
         optgroup->append_single_option_line("support_chamber_temp_control", "printer_basic_information_accessory#support-controlling-chamber-temperature");
         optgroup->append_single_option_line("support_air_filtration", "printer_basic_information_accessory#support-air-filtration");
 
@@ -5892,6 +5893,8 @@ void TabPrinter::toggle_options()
 
         const bool support_parallel_printheads = printer_cfg.opt_bool("support_parallel_printheads");
         toggle_line("parallel_printheads_count", support_parallel_printheads);
+
+        toggle_line("fan_direction", m_config->opt_bool("auxiliary_fan"));
     }