CURA-11966 reduce speed on overhang (#2186)

include/LayerPlan.h

@@ -60,6 +60,12 @@ class LayerPlan : public NoCopy
 #endif
 
 public:
+    struct OverhangMask
+    {
+        Shape supported_region;
+        Ratio speed_ratio;
+    };
+
     const PathConfigStorage configs_storage_; //!< The line configs for this layer for each feature type
     const coord_t z_;
     coord_t final_travel_z_;
@@ -115,7 +121,8 @@ class LayerPlan : public NoCopy
     Comb* comb_;
     coord_t comb_move_inside_distance_; //!< Whenever using the minimum boundary for combing it tries to move the coordinates inside by this distance after calculating the combing.
     Shape bridge_wall_mask_; //!< The regions of a layer part that are not supported, used for bridging
-    Shape overhang_mask_; //!< The regions of a layer part where the walls overhang
+    std::vector<OverhangMask> overhang_masks_; //!< The regions of a layer part where the walls overhang, calculated for multiple overhang angles. The latter is the most
+                                               //!< overhanging. For a visual explanation of the result, see doc/gradual_overhang_speed.svg
     Shape seam_overhang_mask_; //!< The regions of a layer part where the walls overhang, specifically as defined for the seam
     Shape roofing_mask_; //!< The regions of a layer part where the walls are exposed to the air
 
@@ -295,11 +302,11 @@ class LayerPlan : public NoCopy
     void setBridgeWallMask(const Shape& polys);
 
     /*!
-     * Set overhang_mask.
+     * Set overhang_masks.
      *
-     * \param polys The overhung areas of the part currently being processed that will require modified print settings
+     * \param masks The overhung areas of the part currently being processed that will require modified print settings
      */
-    void setOverhangMask(const Shape& polys);
+    void setOverhangMasks(const std::vector<OverhangMask>& masks);
 
     /*!
      * Set seam_overhang_mask.
@@ -393,6 +400,17 @@ class LayerPlan : public NoCopy
         const double fan_speed = GCodePathConfig::FAN_SPEED_DEFAULT,
         const bool travel_to_z = true);
 
+    void addExtrusionMoveWithGradualOverhang(
+        const Point3LL& p,
+        const GCodePathConfig& config,
+        const SpaceFillType space_fill_type,
+        const Ratio& flow = 1.0_r,
+        const Ratio width_factor = 1.0_r,
+        const bool spiralize = false,
+        const Ratio speed_factor = 1.0_r,
+        const double fan_speed = GCodePathConfig::FAN_SPEED_DEFAULT,
+        const bool travel_to_z = true);
+
     /*!
      * Add polygon to the gcode starting at vertex \p startIdx
      * \param polygon The polygon
@@ -1000,13 +1018,6 @@ class LayerPlan : public NoCopy
      * \return The distance from the start of the current wall line to the first bridge segment
      */
     coord_t computeDistanceToBridgeStart(const ExtrusionLine& wall, const size_t current_index, const coord_t min_bridge_line_len) const;
-
-    /*!
-     * \brief Calculates whether the given segment is to be treated as overhanging
-     * \param p0 The start point of the segment
-     * \param p1 The end point of the segment
-     */
-    bool segmentIsOnOverhang(const Point3LL& p0, const Point3LL& p1) const;
 };
 
 } // namespace cura

include/geometry/Shape.h

@@ -256,6 +256,14 @@ class Shape : public LinesSet<Polygon>
      */
     void simplify(ClipperLib::PolyFillType fill_type = ClipperLib::pftEvenOdd);
 
+    /*!
+     * Calculates the intersections between the given segment and all the segments of the shape
+     * @param start The start position of the segment
+     * @param end The end position of the segment
+     * @return The parameters of the intersections on the segment (intersection = start + t * (end - start)), unsorted
+     */
+    std::vector<float> intersectionsWithSegment(const Point2LL& start, const Point2LL& end) const;
+
 #ifdef BUILD_TESTS
     /*!
      * @brief Import the polygon from a WKT string

src/FffGcodeWriter.cpp

@@ -12,6 +12,7 @@
 #include <optional>
 #include <unordered_set>
 
+#include <range/v3/view/chunk_by.hpp>
 #include <range/v3/view/concat.hpp>
 #include <spdlog/spdlog.h>
 
@@ -3082,21 +3083,86 @@ bool FffGcodeWriter::processInsets(
             gcode_layer.setBridgeWallMask(Shape());
         }
 
-        const auto get_overhang_region = [&](const AngleDegrees overhang_angle) -> Shape
+        const Shape fully_supported_region = outlines_below.offset(-half_outer_wall_width);
+        const Shape part_print_region = part.outline.offset(-half_outer_wall_width);
+
+        const auto get_supported_region = [&fully_supported_region, &layer_height](const AngleDegrees& overhang_angle) -> Shape
         {
-            if (overhang_angle >= 90)
-            {
-                return Shape(); // keep empty to disable overhang detection
-            }
             // the overhang mask is set to the area of the current part's outline minus the region that is considered to be supported
             // the supported region is made up of those areas that really are supported by either model or support on the layer below
             // expanded to take into account the overhang angle, the greater the overhang angle, the larger the supported area is
             // considered to be
-            const coord_t overhang_width = layer_height * std::tan(overhang_angle / (180 / std::numbers::pi));
-            return part.outline.offset(-half_outer_wall_width).difference(outlines_below.offset(10 + overhang_width - half_outer_wall_width)).offset(10);
+            if (overhang_angle < 90.0)
+            {
+                const coord_t overhang_width = layer_height * std::tan(AngleRadians(overhang_angle));
+                return fully_supported_region.offset(overhang_width + 10);
+            }
+
+            return Shape();
         };
-        gcode_layer.setOverhangMask(get_overhang_region(mesh.settings.get<AngleDegrees>("wall_overhang_angle")));
-        gcode_layer.setSeamOverhangMask(get_overhang_region(mesh.settings.get<AngleDegrees>("seam_overhang_angle")));
+
+        // Build supported regions for all the overhang speeds. For a visual explanation of the result, see doc/gradual_overhang_speed.svg
+        std::vector<LayerPlan::OverhangMask> overhang_masks;
+        const auto overhang_speed_factors = mesh.settings.get<std::vector<Ratio>>("wall_overhang_speed_factors");
+        const size_t overhang_angles_count = overhang_speed_factors.size();
+        const auto wall_overhang_angle = mesh.settings.get<AngleDegrees>("wall_overhang_angle");
+        if (overhang_angles_count > 0 && wall_overhang_angle < 90.0)
+        {
+            struct SpeedRegion
+            {
+                AngleDegrees overhang_angle;
+                Ratio speed_factor;
+            };
+
+            // Create raw speed regions
+            const AngleDegrees overhang_step = (90.0 - wall_overhang_angle) / static_cast<double>(overhang_angles_count);
+            std::vector<SpeedRegion> speed_regions;
+            speed_regions.reserve(overhang_angles_count + 1);
+
+            speed_regions.push_back(SpeedRegion{ wall_overhang_angle, 1.0_r }); // Initial internal region, always 100% speed factor
+
+            for (size_t angle_index = 1; angle_index < overhang_angles_count; ++angle_index)
+            {
+                const AngleDegrees actual_wall_overhang_angle = wall_overhang_angle + static_cast<double>(angle_index) * overhang_step;
+                const Ratio speed_factor = overhang_speed_factors[angle_index - 1];
+
+                speed_regions.push_back(SpeedRegion{ actual_wall_overhang_angle, speed_factor });
+            }
+
+            speed_regions.push_back(SpeedRegion{ 90.0, overhang_speed_factors.back() }); // Final "everything else" speed region
+
+            // Now merge regions that have similar speed factors (saves calculations and avoid generating micro-segments)
+            auto merged_regions = speed_regions
+                                | ranges::views::chunk_by(
+                                      [](const auto& region_a, const auto& region_b)
+                                      {
+                                          return region_a.speed_factor == region_b.speed_factor;
+                                      });
+
+            // If finally necessary, add actual calculated speed regions
+            if (ranges::distance(merged_regions) > 1)
+            {
+                for (const auto& regions : merged_regions)
+                {
+                    const SpeedRegion& last_region = *ranges::prev(regions.end());
+                    overhang_masks.push_back(LayerPlan::OverhangMask{ get_supported_region(last_region.overhang_angle), last_region.speed_factor });
+                }
+            }
+        }
+        gcode_layer.setOverhangMasks(overhang_masks);
+
+        // the seam overhang mask is set to the area of the current part's outline minus the region that is considered to be supported,
+        // which will then be empty if everything is considered supported i.r.t. the angle
+        const AngleDegrees seam_overhang_angle = mesh.settings.get<AngleDegrees>("seam_overhang_angle");
+        if (seam_overhang_angle < 90.0)
+        {
+            const Shape supported_region_seam = get_supported_region(seam_overhang_angle);
+            gcode_layer.setSeamOverhangMask(part_print_region.difference(supported_region_seam).offset(10));
+        }
+        else
+        {
+            gcode_layer.setSeamOverhangMask(Shape());
+        }
 
         const auto roofing_mask_fn = [&]() -> Shape
         {
@@ -3127,7 +3193,7 @@ bool FffGcodeWriter::processInsets(
         // clear to disable use of bridging settings
         gcode_layer.setBridgeWallMask(Shape());
         // clear to disable overhang detection
-        gcode_layer.setOverhangMask(Shape());
+        gcode_layer.setOverhangMasks({});
         // clear to disable overhang detection
         gcode_layer.setSeamOverhangMask(Shape());
         // clear to disable use of roofing settings