Add NumVert, NumContour, and Warp

src/cross_section/include/cross_section.h

@@ -64,6 +64,8 @@ class CrossSection {
   // Output
   Polygons ToPolygons() const;
   double Area() const;
+  int NumVert() const;
+  int NumContour() const;
   bool IsEmpty() const;
   Rect Bounds() const;
   ///@}
@@ -76,6 +78,7 @@ class CrossSection {
   CrossSection Scale(const glm::vec2 s) const;
   CrossSection Mirror(const glm::vec2 ax) const;
   CrossSection Transform(const glm::mat3x2& m) const;
+  CrossSection Warp(std::function<void(glm::vec2&)> warpFunc) const;
   CrossSection Simplify(double epsilon = 1e-6) const;
   enum class JoinType { Square, Round, Miter };
   CrossSection Offset(double delta, JoinType jt, double miter_limit = 2.0,

src/cross_section/src/cross_section.cpp

@@ -305,6 +305,24 @@ CrossSection CrossSection::Transform(const glm::mat3x2& m) const {
   return transformed;
 }
 
+CrossSection CrossSection::Warp(
+    std::function<void(glm::vec2&)> warpFunc) const {
+  auto paths = GetPaths();
+  auto warped = C2::PathsD();
+  warped.reserve(paths.size());
+  for (auto path : paths) {
+    auto sz = path.size();
+    auto s = C2::PathD(sz);
+    for (int i = 0; i < sz; ++i) {
+      auto v = v2_of_pd(path[i]);
+      warpFunc(v);
+      s[i] = v2_to_pd(v);
+    }
+    warped.push_back(s);
+  }
+  return CrossSection(C2::Union(warped, C2::FillRule::Positive, precision_));
+}
+
 CrossSection CrossSection::Simplify(double epsilon) const {
   auto ps = SimplifyPaths(GetPaths(), epsilon, false);
   return CrossSection(ps);
@@ -320,10 +338,23 @@ CrossSection CrossSection::Offset(double delta, JoinType jointype,
 }
 
 double CrossSection::Area() const { return C2::Area(GetPaths()); }
+
+int CrossSection::NumVert() const {
+  int n = 0;
+  auto paths = GetPaths();
+  for (auto p : paths) {
+    n += p.size();
+  }
+  return n;
+}
+
+int CrossSection::NumContour() const { return GetPaths().size(); }
+
 Rect CrossSection::Bounds() const {
   auto r = C2::GetBounds(GetPaths());
   return Rect({r.left, r.bottom}, {r.right, r.top});
 }
+
 bool CrossSection::IsEmpty() const { return GetPaths().empty(); }
 
 Polygons CrossSection::ToPolygons() const {

test/cross_section_test.cpp

@@ -97,3 +97,17 @@ TEST(CrossSection, Transform) {
   // same transformations are applied in b_copy (giving same result)
   Identical(ex_b, Manifold::Extrude(b_copy, 1.).GetMesh());
 }
+
+TEST(CrossSection, Warp) {
+  auto sq = CrossSection::Square({10., 10.});
+  auto a = sq.Scale({2, 3}).Translate({4, 5});
+  auto b = sq.Warp([](glm::vec2 &v) {
+    v.x = v.x * 2 + 4;
+    v.y = v.y * 3 + 5;
+  });
+
+  EXPECT_EQ(sq.NumVert(), 4);
+  EXPECT_EQ(sq.NumContour(), 1);
+  Identical(Manifold::Extrude(a, 1.).GetMesh(),
+            Manifold::Extrude(b, 1.).GetMesh());
+}