From 716bdb9e3e9609075533906f07d2fbf6a489e86b Mon Sep 17 00:00:00 2001
From: Jacob Spainhour <Jacob.Spainhour@colorado.edu>
Date: Fri, 5 Aug 2022 16:55:08 -0700
Subject: [PATCH] Add split to convex function

---
 src/axom/primal/operators/split.hpp | 52 +++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/src/axom/primal/operators/split.hpp b/src/axom/primal/operators/split.hpp
index 044edcdf58..eb5b5b9be3 100644
--- a/src/axom/primal/operators/split.hpp
+++ b/src/axom/primal/operators/split.hpp
@@ -17,6 +17,11 @@
 #include "axom/primal/geometry/Octahedron.hpp"
 #include "axom/primal/geometry/Tetrahedron.hpp"
 
+#include "axom/primal/geometry/BezierCurve.hpp"
+#include "axom/primal/geometry/Polygon.hpp"
+#include "axom/primal/geometry/CurvedPolygon.hpp"
+#include "axom/primal/operators/is_convex.hpp"
+
 #include "axom/slic.hpp"
 
 // perhaps #include split_impl.hpp here
@@ -78,6 +83,53 @@ void split(const Octahedron<Tp, NDIMS>& oct,
   out.push_back(Tet(oct[Q], oct[S], oct[U], C));
 };
 
+/*!
+ * \brief Splits a BezierCurve object into convex Bezier Curves
+ *
+ * \param [in] c BezierCurve to split
+ * \param [out] out The \a axom::Array of BezierCurve objects; a set of convex
+ *              components of c are appended to out.
+ *
+ * \pre NDIMS == 2
+ *
+ * Uses a bisection method, splitting the curve recursively until each section
+ * is convex.
+ * 
+ */
+template <typename Tp, int NDIMS = 2>
+void split_to_convex(const BezierCurve<Tp, NDIMS>& c,
+                     axom::Array<BezierCurve<Tp, NDIMS>>& out)
+{
+  // Implemented for two dimensions
+  SLIC_ASSERT(NDIMS == 2);
+
+  using Poly = Polygon<Tp, NDIMS>;
+  using Bez = BezierCurve<Tp, NDIMS>;
+
+  if(is_convex(Poly(c.getControlPoints())))
+    out.push_back(Bez(c));
+  else
+  {
+    Bez c1, c2;
+    c.split(0.5, c1, c2);
+    split_to_convex(c1, out);
+    split_to_convex(c2, out);
+  }
+}
+
+template <typename Tp, int NDIMS = 2>
+void split_to_convex(const CurvedPolygon<Tp, NDIMS>& cpoly,
+                     axom::Array<BezierCurve<Tp, NDIMS>>& out)
+{
+  // Implemented for two dimensions
+  SLIC_ASSERT(NDIMS == 2);
+
+  using Poly = Polygon<Tp, NDIMS>;
+  using Bez = BezierCurve<Tp, NDIMS>;
+
+  for(int i = 0; i < cpoly.numEdges(); i++) split_to_convex(cpoly[i], out);
+}
+
 }  // namespace primal
 }  // namespace axom