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={ {(0,0,0),(1,0,0),(1,0,0),(2,0,0)}, {(0,4/3,0),(2/3,4/3,2),(4/3,4/3,2),(2,4/3,0)}, {(0,2/3,0),(2/3,2/3,0),(4/3,2/3,0),(2,2/3,0)}, {(0,2,0),(2/3,2,0),(4/3,2,0),(2,2,0)} }; triple[][] B={ {(0.5,0,-1),(0.5,1,-1),(0.5,2,-1),(0.5,3,-1)}, {(0.5,0,0),(0.5,1,0),(0.5,2,0),(0.5,3,0)}, {(0.5,0,1),(0.5,1,1),(0.5,2,1),(0.5,3,1)}, {(0.5,0,2),(0.5,1,2),(0.5,2,2),(0.5,3,2)} }; split S=split(B,A); defaultrender.merge=true; 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));