1 files changed, 64 insertions, 5 deletions
diff --git a/Build/source/utils/asymptote/examples/splitpatch.asy b/Build/source/utils/asymptote/examples/splitpatch.asy
index f1f5b6b98ba..2e9fae66431 100644
--- a/Build/source/utils/asymptote/examples/splitpatch.asy
+++ b/Build/source/utils/asymptote/examples/splitpatch.asy
@@ -2,6 +2,64 @@ import three;
 
 size(300);
 
+// A structure to subdivide two intersecting patches about their intersection.
+struct split
+{
+  surface[] S=sequence(new surface(int i) {return new surface;},1);
+  surface[] T=sequence(new surface(int i) {return new surface;},1);
+
+  struct tree {
+    tree[] tree=new tree[2];
+  }
+  // Default subdivision depth.
+  int n=20;
+
+  // Subdivide p and q to depth n if they overlap.
+  void write(tree pt, tree qt, triple[][] p, triple[][] q, int depth=n) {
+    --depth;
+    triple[][][] Split(triple[][] P)=depth % 2 == 0 ? hsplit : vsplit;
+    triple[][][] P=Split(p);
+    triple[][][] Q=Split(q);
+
+    for(int i=0; i < 2; ++i) {
+      triple[][] Pi=P[i];
+      for(int j=0; j < 2; ++j) {
+        triple[][] Qj=Q[j];
+        if(overlap(Pi,Qj)) {
+          if(!pt.tree.initialized(i))
+            pt.tree[i]=new tree;
+          if(!qt.tree.initialized(j))
+            qt.tree[j]=new tree;
+          if(depth > 0)
+            write(pt.tree[i],qt.tree[j],Pi,Qj,depth);
+        }
+      }    
+    }
+  }
+  
+  // Output the subpatches of p from subdivision.
+  void read(surface[] S, tree t, triple[][] p, int depth=n) {
+    --depth;
+    triple[][][] Split(triple[][] P)=depth % 2 == 0 ? hsplit : vsplit;
+    triple[][][] P=Split(p);
+
+    for(int i=0; i < 2; ++i) {
+      if(t.tree.initialized(i)) 
+        read(S,t.tree[i],P[i],depth);
+      else {
+        S[0].push(patch(P[i]));
+      }
+    }
+  }
+
+  void operator init(triple[][] p, triple[][] q, int depth=n) {
+    tree ptrunk,qtrunk;
+    write(ptrunk,qtrunk,p,q,depth);
+    read(T,ptrunk,p,depth);
+    read(S,qtrunk,q,depth);
+  }
+}
+
 currentprojection=orthographic(0,0,1);
 
 triple[][] A={
@@ -18,11 +76,12 @@ triple[][] B={
   {(0.5,0,2),(0.5,1,2),(0.5,2,2),(0.5,3,2)}
 };
 
-split S=split(A,B,10);
-//write(S.T.length);
+split S=split(B,A);
 
 defaultrender.merge=true;
 
-for(int i=0; i < S.T.length; ++i)
-  draw(surface(patch(S.T[i])),Pen(i));
-draw(surface(patch(B)),blue);
+for(int i=0; i < S.S[0].s.length; ++i)
+  draw(surface(S.S[0].s[i]),Pen(i));
+
+for(int i=0; i < S.T[0].s.length; ++i)
+  draw(surface(S.T[0].s[i]),Pen(i));