Implemented linear tapering of extrusion rate for the 1st spiral vase layer

above the solid infill. Should fix
first layer of vase (after bottom layers) is bulging (0.6nozzle, 0.4 layerhight) #3712
Adjust flow of the "second" layer in spiral vase mode #2795

src/libslic3r/GCode.cpp

@@ -1764,6 +1764,7 @@ void GCode::process_layer(
 
     // Check whether it is possible to apply the spiral vase logic for this layer.
     // Just a reminder: A spiral vase mode is allowed for a single object, single material print only.
+    m_enable_loop_clipping = true;
     if (m_spiral_vase && layers.size() == 1 && support_layer == nullptr) {
         bool enable = (layer.id() > 0 || print.config().brim_width.value == 0.) && (layer.id() >= (size_t)print.config().skirt_height.value && ! print.has_infinite_skirt());
         if (enable) {
@@ -1775,10 +1776,10 @@ void GCode::process_layer(
                     break;
                 }
         }
-        m_spiral_vase->enable = enable;
+        m_spiral_vase->enable(enable);
+        // If we're going to apply spiralvase to this layer, disable loop clipping.
+        m_enable_loop_clipping = !enable;
     }
-    // If we're going to apply spiralvase to this layer, disable loop clipping
-    m_enable_loop_clipping = ! m_spiral_vase || ! m_spiral_vase->enable;
 
     std::string gcode;
 

src/libslic3r/GCode/SpiralVase.cpp

@@ -16,7 +16,7 @@ std::string SpiralVase::process_layer(const std::string &gcode)
     
     // If we're not going to modify G-code, just feed it to the reader
     // in order to update positions.
-    if (! this->enable) {
+    if (! m_enabled) {
         m_reader.parse_buffer(gcode);
         return gcode;
     }
@@ -50,7 +50,10 @@ std::string SpiralVase::process_layer(const std::string &gcode)
     z -= layer_height;
     
     std::string new_gcode;
-    m_reader.parse_buffer(gcode, [&new_gcode, &z, &layer_height, &total_layer_length]
+    bool  transition = m_transition_layer;
+    float layer_height_factor = layer_height / total_layer_length;
+    float len = 0.f;
+    m_reader.parse_buffer(gcode, [&new_gcode, &z, total_layer_length, layer_height_factor, transition, &len]
         (GCodeReader &reader, GCodeReader::GCodeLine line) {
         if (line.cmd_is("G1")) {
             if (line.has_z()) {
@@ -64,8 +67,11 @@ std::string SpiralVase::process_layer(const std::string &gcode)
                 if (dist_XY > 0) {
                     // horizontal move
                     if (line.extruding(reader)) {
-                        z += dist_XY * layer_height / total_layer_length;
+                        len += dist_XY;
-                        line.set(reader, Z, z);
+                        line.set(reader, Z, z + len * layer_height_factor);
+                        if (transition && line.has(E))
+                            // Transition layer, modulate the amount of extrusion from zero to the final value.
+                            line.set(reader, E, line.value(E) * len / total_layer_length);
                         new_gcode += line.raw() + '\n';
                     }
                     return;

src/libslic3r/GCode/SpiralVase.hpp

@@ -8,18 +8,26 @@ namespace Slic3r {
 
 class SpiralVase {
 public:
-    bool enable = false;
-    
     SpiralVase(const PrintConfig &config) : m_config(&config)
     {
         m_reader.z() = (float)m_config->z_offset;
         m_reader.apply_config(*m_config);
     };
+
+    void 		enable(bool en) {
+   		m_transition_layer = en && ! m_enabled;
+    	m_enabled 		   = en;
+    }
+
     std::string process_layer(const std::string &gcode);
     
 private:
     const PrintConfig  *m_config;
     GCodeReader 		m_reader;
+
+    bool 				m_enabled = false;
+    // First spiral vase layer. Layer height has to be ramped up from zero to the target layer height.
+    bool 				m_transition_layer = false;
 };
 
 }