ENH: Improve CrossHatch transation layers

jira: 6701

Change name from Flippingline to CrossHatch.

Reduce noise, improve speed by 6.5%. Improve transation layers by
gradually increasing rotation angle and overshoot the transation
layer while direction changed.

Change-Id: I17fcc45b409074d121bf5bb5702e15553d925b51

src/libslic3r/CMakeLists.txt

@@ -84,8 +84,8 @@ set(lisbslic3r_sources
     Fill/FillConcentric.hpp
     Fill/FillConcentricInternal.cpp
     Fill/FillConcentricInternal.hpp
-    Fill/FillFlippingLine.cpp
-    Fill/FillFlippingLine.hpp
+    Fill/FillCrossHatch.cpp
+    Fill/FillCrossHatch.hpp
     Fill/FillHoneycomb.cpp
     Fill/FillHoneycomb.hpp
     Fill/FillGyroid.cpp

src/libslic3r/Fill/FillBase.cpp

@@ -23,7 +23,7 @@
 #include "FillLightning.hpp"
 // BBS: new infill pattern header
 #include "FillConcentricInternal.hpp"
-#include "FillFlippingLine.hpp"
+#include "FillCrossHatch.hpp"
 
 // #define INFILL_DEBUG_OUTPUT
 
@@ -38,7 +38,7 @@ Fill* Fill::new_from_type(const InfillPattern type)
     case ipGyroid:              return new FillGyroid();
     case ipRectilinear:         return new FillRectilinear();
     case ipAlignedRectilinear:  return new FillAlignedRectilinear();
-    case ipFlippingLine:        return new FillFlippingLine();
+    case ipCrossHatch:          return new FillCrossHatch();
     case ipMonotonic:           return new FillMonotonic();
     case ipLine:                return new FillLine();
     case ipGrid:                return new FillGrid();

src/libslic3r/Fill/FillCrossHatch.cpp

@@ -2,14 +2,14 @@
 #include "../ShortestPath.hpp"
 #include "../Surface.hpp"
 
-#include "FillFlippingLine.hpp"
+#include "FillCrossHatch.hpp"
 
 namespace Slic3r {
 
-// FlipLines Infill: Enhances 3D Printing Speed & Reduces Noise
-// FlipLines, as its name hints, alternates line direction by 90 degrees every few layers to improve adhesion.
+// CrossHatch Infill: Enhances 3D Printing Speed & Reduces Noise
+// CrossHatch, as its name hints, alternates line direction by 90 degrees every few layers to improve adhesion.
 // It introduces transform layers between direction shifts for better line cohesion, which fixes the weakness of line infill.
-// The transform technique is inspired by David Eccles, improved 3D honeycomb but also a more flexible implementation.
+// The transform technique is inspired by David Eccles, improved 3D honeycomb but we made a more flexible implementation.
 // This method notably increases printing speed, meeting the demands of modern high-speed 3D printers, and reduces noise for most layers.
 // By Bambu Lab
 
@@ -22,15 +22,6 @@ namespace Slic3r {
  *            \     /
  *             o---o
  *   p1   p2  p3   p4
- *
- *   // X1 = progress * (1/8) * period
- *   // X2 = ( (1/2 - progress) * (1/8) ) * period
- *   // X3 = X1 + (1/2) * period
- *   // X4 = ( (1 - progress) * (1/8) ) * period
- *   // Y1 = X1
- *   // Y2 = X1
- *   // Y3 = -X1
- *   // Y4 = -X1
  */
 
 static Pointfs generate_one_cycle(double progress, coordf_t period)
@@ -38,10 +29,10 @@ static Pointfs generate_one_cycle(double progress, coordf_t period)
     Pointfs out;
     double  offset = progress * 1. / 8. * period;
     out.reserve(4);
-    out.push_back(Vec2d(offset, offset));
-    out.push_back(Vec2d(0.5 * period - offset, offset));
-    out.push_back(Vec2d(0.5 * period + offset, -offset));
-    out.push_back(Vec2d(1. * period - offset, -offset));
+    out.push_back(Vec2d(0.25 * period - offset, offset));
+    out.push_back(Vec2d(0.25 * period + offset, offset));
+    out.push_back(Vec2d(0.75 * period - offset, -offset));
+    out.push_back(Vec2d(0.75 * period + offset, -offset));
     return out;
 }
 
@@ -154,8 +145,9 @@ static Polylines generate_repeat_pattern(int direction, coordf_t grid_size, coor
 static Polylines generate_infill_layers(coordf_t z_height, double repeat_ratio, coordf_t grid_size, coordf_t width, coordf_t height)
 {
     Polylines result;
-    coordf_t  trans_layer_size  = grid_size * 0.3;          // upper.
+    coordf_t  trans_layer_size  = grid_size * 0.4;          // upper.
     coordf_t  repeat_layer_size = grid_size * repeat_ratio; // lower.
+    z_height                    += repeat_layer_size / 2;   // offset to improve first few layer strength
     coordf_t  period            = trans_layer_size + repeat_layer_size;
     coordf_t  remains           = z_height - std::floor(z_height / period) * period;
     coordf_t  trans_z           = remains - repeat_layer_size; // put repeat layer first.
@@ -174,15 +166,15 @@ static Polylines generate_infill_layers(coordf_t z_height, double repeat_ratio,
 
         // split the progress to forward and backward, with a opposite direction.
         if (progress < 0.5)
-            result = generate_transform_pattern(progress * 2, direction, grid_size, width, height);
+            result = generate_transform_pattern((progress + 0.1) * 2, direction, grid_size, width, height); // increase overlapping.
         else
-            result = generate_transform_pattern((1 - progress) * 2, -1 * direction, grid_size, width, height);
+            result = generate_transform_pattern((1.1 - progress) * 2, -1 * direction, grid_size, width, height);
     }
 
     return result;
 }
 
-void FillFlippingLine ::_fill_surface_single(
+void FillCrossHatch ::_fill_surface_single(
     const FillParams &params, unsigned int thickness_layers, const std::pair<float, Point> &direction, ExPolygon expolygon, Polylines &polylines_out)
 {
     // rotate angle

src/libslic3r/Fill/FillCrossHatch.hpp

@@ -1,5 +1,5 @@
-#ifndef slic3r_FillFlippingLines_hpp_
-#define slic3r_FillFlippingLines_hpp_
+#ifndef slic3r_FillCrossHatch_hpp_
+#define slic3r_FillCrossHatch_hpp_
 
 #include <map>
 
@@ -9,11 +9,11 @@
 
 namespace Slic3r {
 
-class FillFlippingLine : public Fill
+class FillCrossHatch : public Fill
 {
 public:
-    Fill *clone() const override { return new FillFlippingLine(*this); };
-    ~FillFlippingLine() override {}
+    Fill *clone() const override { return new FillCrossHatch(*this); };
+    ~FillCrossHatch() override {}
 
 protected:
 	void _fill_surface_single(
@@ -26,4 +26,4 @@ protected:
 
 } // namespace Slic3r
 
-#endif // slic3r_FillFlippingLines_hpp_
+#endif // slic3r_FillCrossHatch_hpp_

src/libslic3r/PrintConfig.cpp

@@ -135,7 +135,7 @@ static t_config_enum_values s_keys_map_InfillPattern {
     { "octagramspiral",     ipOctagramSpiral },
     { "supportcubic",       ipSupportCubic },
     { "lightning",          ipLightning },
-    { "flippingline",        ipFlippingLine}
+    { "crosshatch",         ipCrossHatch}
 };
 CONFIG_OPTION_ENUM_DEFINE_STATIC_MAPS(InfillPattern)
 
@@ -1603,7 +1603,7 @@ void PrintConfigDef::init_fff_params()
     def->enum_values.push_back("octagramspiral");
     def->enum_values.push_back("supportcubic");
     def->enum_values.push_back("lightning");
-    def->enum_values.push_back("flippingline");
+    def->enum_values.push_back("crosshatch");
     def->enum_labels.push_back(L("Concentric"));
     def->enum_labels.push_back(L("Rectilinear"));
     def->enum_labels.push_back(L("Grid"));
@@ -1621,7 +1621,7 @@ void PrintConfigDef::init_fff_params()
     def->enum_labels.push_back(L("Octagram Spiral"));
     def->enum_labels.push_back(L("Support Cubic"));
     def->enum_labels.push_back(L("Lightning"));
-    def->enum_labels.push_back(L("Flipping Line"));
+    def->enum_labels.push_back(L("Cross Hatch"));
     def->set_default_value(new ConfigOptionEnum<InfillPattern>(ipCubic));
 
     def = this->add("top_surface_acceleration", coFloat);

src/libslic3r/PrintConfig.hpp

@@ -54,8 +54,8 @@ enum AuthorizationType {
 enum InfillPattern : int {
     ipConcentric, ipRectilinear, ipGrid, ipLine, ipCubic, ipTriangles, ipStars, ipGyroid, ipHoneycomb, ipAdaptiveCubic, ipMonotonic, ipMonotonicLine, ipAlignedRectilinear, ip3DHoneycomb,
     ipHilbertCurve, ipArchimedeanChords, ipOctagramSpiral, ipSupportCubic, ipSupportBase, ipConcentricInternal,
-    ipLightning, ipFlippingLine,
-ipCount,
+    ipLightning, ipCrossHatch,
+    ipCount,
 };
 
 enum class IroningType {

src/libslic3r/PrintObject.cpp

@@ -2217,7 +2217,7 @@ void PrintObject::bridge_over_infill()
         // Check it the infill that require a fixed infill angle.
         switch (dominant_pattern) {
         case ip3DHoneycomb:
-        case ipFlippingLine:
+        case ipCrossHatch:
             return (infill_direction + 45.0) * 2.0 * M_PI / 360.;
         default: break;
         }