polygon offsets: scale arc tolerance width offset distance

Ultimaker · Sep 1, 2022 · 4d81c52 · 4d81c52
1 parent 29ab836
commit 4d81c52
Show file tree

Hide file tree

Showing 2 changed files with 20 additions and 13 deletions.
diff --git a/include/utils/polygon.h b/include/utils/polygon.h
@@ -59,8 +59,6 @@ class ListPolyIt;
 typedef std::list<Point> ListPolygon; //!< A polygon represented by a linked list instead of a vector
 typedef std::vector<ListPolygon> ListPolygons; //!< Polygons represented by a vector of linked lists instead of a vector of vectors
 
-// Allowed deviation for round joint while offsetting (this reduces the number of segment, http://www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Classes/ClipperOffset/Properties/ArcTolerance.htm)
-static constexpr double clipper_arc_tolerance = INT_EPSILON;
 // How far a miter can be offseted before being truncated, relative to the offset size (http://www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Classes/ClipperOffset/Properties/MiterLimit.htm)
 static constexpr double clipper_miter_limit = 1.2;
 static constexpr int clipper_init = 0;
@@ -398,6 +396,11 @@ class ConstPolygonRef
      * \param[in,out] backward_is_too_far Whether trying another step backward is blocked by the shortcut length condition. Updated for the next iteration.
      */
     static void smooth_outward_step(const Point p1, const int64_t shortcut_length2, ListPolyIt& p0_it, ListPolyIt& p2_it, bool& forward_is_blocked, bool& backward_is_blocked, bool& forward_is_too_far, bool& backward_is_too_far);
+
+
+    /// Allowed deviation for round joints while offsetting (this reduces the number of segment
+    /// @see http://www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Classes/ClipperOffset/Properties/ArcTolerance.htm
+    static double calcArcTolerance(int offset);
 };
 
 
@@ -1014,7 +1017,7 @@ class Polygons
     {
         Polygons ret;
         ClipperLib::EndType end_type = (joinType == ClipperLib::jtMiter)? ClipperLib::etOpenSquare : ClipperLib::etOpenRound;
-        ClipperLib::ClipperOffset clipper(clipper_miter_limit, clipper_arc_tolerance);
+        ClipperLib::ClipperOffset clipper(clipper_miter_limit, ConstPolygonRef::calcArcTolerance(distance));
         clipper.AddPaths(paths, joinType, end_type);
         clipper.MiterLimit = clipper_miter_limit;
         clipper.Execute(ret.paths, distance);

diff --git a/src/utils/polygon.cpp b/src/utils/polygon.cpp
@@ -86,7 +86,7 @@ Polygons Polygons::approxConvexHull(int extra_outset)
     for (const ClipperLib::Path& path : paths)
     {
         Polygons offset_result;
-        ClipperLib::ClipperOffset offsetter(clipper_miter_limit, clipper_arc_tolerance);
+        ClipperLib::ClipperOffset offsetter(clipper_miter_limit, ConstPolygonRef::calcArcTolerance(overshoot));
         offsetter.AddPath(path, ClipperLib::jtRound, ClipperLib::etClosedPolygon);
         offsetter.Execute(offset_result.paths, overshoot);
         convex_hull.add(offset_result);
@@ -281,7 +281,7 @@ Polygons Polygons::intersectionPolyLines(const Polygons& polylines, bool restitc
     if (restitch)
     {
         Polygons result_lines, result_polygons;
-        const coord_t snap_distance = clipper_arc_tolerance;
+        const coord_t snap_distance = INT_EPSILON;
         PolylineStitcher<Polygons, Polygon, Point>::stitch(ret, result_lines, result_polygons, max_stitch_distance, snap_distance);
         ret = result_lines;
         // if polylines got stitched into polygons, split them back up into a polyline again, because the result only admits polylines
@@ -339,30 +339,34 @@ coord_t Polygons::polyLineLength() const
 
 Polygons Polygons::offset(int distance, ClipperLib::JoinType join_type, double miter_limit) const
 {
-    if (distance == 0)
+    if (std::abs(distance) < INT_EPSILON / 2)
     {
         return *this;
     }
     Polygons ret;
-    ClipperLib::ClipperOffset clipper(miter_limit, clipper_arc_tolerance);
+    ClipperLib::ClipperOffset clipper(miter_limit, ConstPolygonRef::calcArcTolerance(distance));
     clipper.AddPaths(unionPolygons().paths, join_type, ClipperLib::etClosedPolygon);
-    clipper.MiterLimit = miter_limit;
+    assert(clipper.MiterLimit == miter_limit);
     clipper.Execute(ret.paths, distance);
     return ret;
 }
 
+double ConstPolygonRef::calcArcTolerance(int offset) {
+    constexpr double min_tol = std::max<double>(5_mu, INT_EPSILON);
+    return std::max(min_tol, std::abs(static_cast<double>(offset)) * 1e-2);
+}
+
 Polygons ConstPolygonRef::offset(int distance, ClipperLib::JoinType join_type, double miter_limit) const
 {
-    if (distance == 0)
+    Polygons ret;
+    if (std::abs(distance) < INT_EPSILON / 2)
     {
-        Polygons ret;
         ret.add(*this);
         return ret;
     }
-    Polygons ret;
-    ClipperLib::ClipperOffset clipper(miter_limit, clipper_arc_tolerance);
+    ClipperLib::ClipperOffset clipper(miter_limit, calcArcTolerance(distance));
     clipper.AddPath(*path, join_type, ClipperLib::etClosedPolygon);
-    clipper.MiterLimit = miter_limit;
+    assert(clipper.MiterLimit == miter_limit);
     clipper.Execute(ret.paths, distance);
     return ret;
 }