Add external_perimeter_fan_speed setting

Adds a new seting and plumbs through the UI to independently control
the fan speed for external perimeters. Filed as issue prusa3d#2776.

src/libslic3r/GCode/CoolingBuffer.cpp

@@ -677,12 +677,16 @@ std::string CoolingBuffer::apply_layer_cooldown(
     int  fan_speed          = -1;
     bool bridge_fan_control = false;
     int  bridge_fan_speed   = 0;
-    auto change_extruder_set_fan = [ this, layer_id, layer_time, &new_gcode, &fan_speed, &bridge_fan_control, &bridge_fan_speed ]() {
+    int  external_perimeter_fan_speed = 0;
+    bool in_external_perimeter = false;
+    auto change_extruder_set_fan = [ this, layer_id, layer_time, &new_gcode, &fan_speed, &bridge_fan_control, &bridge_fan_speed, &external_perimeter_fan_speed, &in_external_perimeter]() {
+        in_external_perimeter = false;
         const FullPrintConfig &config = m_gcodegen.config();
 #define EXTRUDER_CONFIG(OPT) config.OPT.get_at(m_current_extruder)
         int min_fan_speed = EXTRUDER_CONFIG(min_fan_speed);
         int fan_speed_new = EXTRUDER_CONFIG(fan_always_on) ? min_fan_speed : 0;
         if (layer_id >= (size_t)EXTRUDER_CONFIG(disable_fan_first_layers)) {
+            external_perimeter_fan_speed = EXTRUDER_CONFIG(external_perimeter_fan_speed);
             int   max_fan_speed             = EXTRUDER_CONFIG(max_fan_speed);
             float slowdown_below_layer_time = float(EXTRUDER_CONFIG(slowdown_below_layer_time));
             float fan_below_layer_time      = float(EXTRUDER_CONFIG(fan_below_layer_time));
@@ -696,6 +700,9 @@ std::string CoolingBuffer::apply_layer_cooldown(
                     double t = (layer_time - slowdown_below_layer_time) / (fan_below_layer_time - slowdown_below_layer_time);
                     fan_speed_new = int(floor(t * min_fan_speed + (1. - t) * max_fan_speed) + 0.5);
                 }
+                // Use the higher of the adjusted speeds if both external perimeter and automatic cooling are enabled.
+                if (external_perimeter_fan_speed && fan_speed_new > external_perimeter_fan_speed)
+                    external_perimeter_fan_speed = fan_speed_new;
             }
             bridge_fan_speed   = EXTRUDER_CONFIG(bridge_fan_speed);
 #undef EXTRUDER_CONFIG
@@ -704,6 +711,7 @@ std::string CoolingBuffer::apply_layer_cooldown(
             bridge_fan_control = false;
             bridge_fan_speed   = 0;
             fan_speed_new      = 0;
+            external_perimeter_fan_speed = 0;
         }
         if (fan_speed_new != fan_speed) {
             fan_speed = fan_speed_new;
@@ -718,6 +726,16 @@ std::string CoolingBuffer::apply_layer_cooldown(
     for (const CoolingLine *line : lines) {
         const char *line_start  = gcode.c_str() + line->line_start;
         const char *line_end    = gcode.c_str() + line->line_end;
+
+        // Adjust the fan speed for external perimeters only when the setting is enabled and we would need to adjust the speed.
+        bool adjust_fan_speed_on_external_perimeter = !!external_perimeter_fan_speed && fan_speed != external_perimeter_fan_speed;
+
+        if (adjust_fan_speed_on_external_perimeter) {
+            bool prev_in_external_perimeter = in_external_perimeter;
+            in_external_perimeter = line->type & CoolingLine::TYPE_EXTERNAL_PERIMETER;
+            adjust_fan_speed_on_external_perimeter = in_external_perimeter != prev_in_external_perimeter;
+        }
+
         if (line_start > pos)
             new_gcode.append(pos, line_start - pos);
         if (line->type & CoolingLine::TYPE_SET_TOOL) {
@@ -734,8 +752,12 @@ std::string CoolingBuffer::apply_layer_cooldown(
             if (bridge_fan_control)
                 new_gcode += m_gcodegen.writer().set_fan(fan_speed, true);
         } else if (line->type & CoolingLine::TYPE_EXTRUDE_END) {
-            // Just remove this comment.
+            if (adjust_fan_speed_on_external_perimeter)
+                new_gcode += m_gcodegen.writer().set_fan(fan_speed, true);
         } else if (line->type & (CoolingLine::TYPE_ADJUSTABLE | CoolingLine::TYPE_EXTERNAL_PERIMETER | CoolingLine::TYPE_WIPE | CoolingLine::TYPE_HAS_F)) {
+            if (adjust_fan_speed_on_external_perimeter)
+                new_gcode += m_gcodegen.writer().set_fan(external_perimeter_fan_speed, true);
+
             // Find the start of a comment, or roll to the end of line.
             const char *end = line_start;
             for (; end < line_end && *end != ';'; ++ end);

src/libslic3r/Preset.cpp

@@ -444,7 +444,7 @@ const std::vector<std::string>& Preset::filament_options()
         "filament_cooling_initial_speed", "filament_cooling_final_speed", "filament_ramming_parameters", "filament_minimal_purge_on_wipe_tower",
         "temperature", "first_layer_temperature", "bed_temperature", "first_layer_bed_temperature", "fan_always_on", "cooling", "min_fan_speed",
         "max_fan_speed", "bridge_fan_speed", "disable_fan_first_layers", "fan_below_layer_time", "slowdown_below_layer_time", "min_print_speed",
-        "start_filament_gcode", "end_filament_gcode",
+        "start_filament_gcode", "end_filament_gcode", "external_perimeter_fan_speed",
         // Retract overrides
         "filament_retract_length", "filament_retract_lift", "filament_retract_lift_above", "filament_retract_lift_below", "filament_retract_speed", "filament_deretract_speed", "filament_retract_restart_extra", "filament_retract_before_travel",
         "filament_retract_layer_change", "filament_wipe", "filament_retract_before_wipe",

src/libslic3r/Print.cpp

@@ -85,6 +85,7 @@ bool Print::invalidate_state_by_config_options(const std::vector<t_config_option
         "duplicate_distance",
         "end_gcode",
         "end_filament_gcode",
+        "external_perimeter_fan_speed",
         "extrusion_axis",
         "extruder_clearance_height",
         "extruder_clearance_radius",

src/libslic3r/PrintConfig.cpp

@@ -489,6 +489,18 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloatOrPercent(0, false));
 
+    def = this->add("external_perimeter_fan_speed", coInts);
+    def->label = L("External perimeter fan speed");
+    def->tooltip = L("When set to a non-zero value this fan speed is used only for external perimeters (visible ones). "
+                    "When set to zero the normal fan speed is used on external perimeters. "
+                    "External perimeters can benefit from higher fan speed to improve surface finish, "
+                    "while internal perimeters, infill, etc. benefit from lower fan speed to improve layer adhesion.");
+    def->sidetext = L("%");
+    def->min = 0;
+    def->max = 100;
+    def->mode = comExpert;
+    def->set_default_value(new ConfigOptionInts { 0 });
+
     def = this->add("external_perimeter_speed", coFloatOrPercent);
     def->label = L("External perimeters");
     def->category = L("Speed");

src/libslic3r/PrintConfig.hpp

@@ -832,6 +832,7 @@ class PrintConfig : public MachineEnvelopeConfig, public GCodeConfig
     ConfigOptionFloat               default_acceleration;
     ConfigOptionInts                disable_fan_first_layers;
     ConfigOptionFloat               duplicate_distance;
+    ConfigOptionInts                external_perimeter_fan_speed;
     ConfigOptionFloat               extruder_clearance_height;
     ConfigOptionFloat               extruder_clearance_radius;
     ConfigOptionStrings             extruder_colour;
@@ -905,6 +906,7 @@ class PrintConfig : public MachineEnvelopeConfig, public GCodeConfig
         OPT_PTR(default_acceleration);
         OPT_PTR(disable_fan_first_layers);
         OPT_PTR(duplicate_distance);
+        OPT_PTR(external_perimeter_fan_speed);
         OPT_PTR(extruder_clearance_height);
         OPT_PTR(extruder_clearance_radius);
         OPT_PTR(extruder_colour);

src/slic3r/GUI/Tab.cpp

@@ -1804,6 +1804,7 @@ void TabFilament::build()
         line.append_option(optgroup->get_option("max_fan_speed"));
         optgroup->append_line(line);
 
+        optgroup->append_single_option_line("external_perimeter_fan_speed");
         optgroup->append_single_option_line("bridge_fan_speed");
         optgroup->append_single_option_line("disable_fan_first_layers");