Improve performance by migrating to Clipper2 2.0.1 (#15969)

Co-authored-by: Rodrigo Faselli <162915171+RF47@users.noreply.github.com>

src/libslic3r/ClipperZUtils.cpp

@@ -0,0 +1,77 @@
+#include "ClipperZUtils.hpp"
+
+#include <clipper2/clipper2_z.hpp>
+
+namespace Slic3r {
+namespace ClipperZUtils {
+
+namespace C2 = Clipper2Lib_Z;
+
+static C2::Paths64 to_paths64(const ZPaths &paths)
+{
+    C2::Paths64 out;
+    out.reserve(paths.size());
+    for (const ZPath &path : paths) {
+        C2::Path64 &dst = out.emplace_back();
+        dst.reserve(path.size());
+        for (const ZPoint &pt : path)
+            dst.emplace_back(pt.x(), pt.y(), pt.z());
+    }
+    return out;
+}
+
+static void append_zpaths(const C2::Paths64 &paths, ZPaths &out)
+{
+    out.reserve(out.size() + paths.size());
+    for (const C2::Path64 &path : paths) {
+        ZPath &dst = out.emplace_back();
+        dst.reserve(path.size());
+        for (const C2::Point64 &pt : path)
+            dst.emplace_back(pt.x, pt.y, pt.z);
+    }
+}
+
+double area(const ZPath &path)
+{
+    const size_t size = path.size();
+    if (size < 3)
+        return 0.;
+    double a = 0.;
+    for (size_t i = 0, j = size - 1; i < size; j = i ++)
+        a += (double(path[j].x()) + path[i].x()) * (double(path[j].y()) - path[i].y());
+    return -a * 0.5;
+}
+
+ZPaths clip_zpaths(ClipType clip_type, const ZPaths &subject, bool subject_open, const ZPaths &clip, const ZFillCallback &zfill, bool preserve_collinear)
+{
+    C2::Clipper64 clipper;
+    clipper.PreserveCollinear(preserve_collinear);
+    if (zfill)
+        clipper.SetZCallback([&zfill](const C2::Point64 &e1bot, const C2::Point64 &e1top, const C2::Point64 &e2bot, const C2::Point64 &e2top, C2::Point64 &pt) {
+            // Clipper2 already copied Z from a coincident input vertex.
+            auto coincident = [&pt](const C2::Point64 &p) { return p.x == pt.x && p.y == pt.y; };
+            if (coincident(e1bot) || coincident(e1top) || coincident(e2bot) || coincident(e2top))
+                return;
+            ZPoint zpt(pt.x, pt.y, pt.z);
+            zfill(ZPoint(e1bot.x, e1bot.y, e1bot.z), ZPoint(e1top.x, e1top.y, e1top.z),
+                  ZPoint(e2bot.x, e2bot.y, e2bot.z), ZPoint(e2top.x, e2top.y, e2top.z), zpt);
+            pt.z = zpt.z();
+        });
+    if (subject_open)
+        clipper.AddOpenSubject(to_paths64(subject));
+    else
+        clipper.AddSubject(to_paths64(subject));
+    clipper.AddClip(to_paths64(clip));
+    const C2::ClipType type = clip_type == ctIntersection ? C2::ClipType::Intersection :
+                              clip_type == ctUnion        ? C2::ClipType::Union :
+                              clip_type == ctDifference   ? C2::ClipType::Difference : C2::ClipType::Xor;
+    C2::Paths64 closed, open;
+    clipper.Execute(type, C2::FillRule::NonZero, closed, open);
+    ZPaths out;
+    append_zpaths(closed, out);
+    append_zpaths(open, out);
+    return out;
+}
+
+} // namespace ClipperZUtils
+} // namespace Slic3r