// CORNER TABLE FOR TRIANGLE MESHES by Jarek Rosignac
// Last edited Feb 17, 2008

Mesh M = new Mesh();     // creates a default triangle meshvoid computeValenceAndResetNormals() {      // caches valence of each vertex
 
//========================== class MESH ===============================
class Mesh {

//  ==================================== INIT, CREATE, COPY ====================================
 Mesh() {}
 int maxnv = 30000;                         //  max number of vertices
 int maxnt = maxnv*2;                       // max number of triangles
 void declare() {c=0; sc=0; prevc=0;
   for (int i=0; i<maxnv; i++) {G[i]=new pt(0,0,0); Nv[i]=new vec(0,0,0);};   // init vertices and normals
   for (int i=0; i<maxnt; i++) {Nt[i]=new vec(0,0,0); visible[i]=true;} ;}       // init triangle normals and skeleton lab els
 void init() {c=0; prevc=0; sc=0; nv=0; nt=0; nc=0;  for (int i=0; i<maxnt; i++) visible[i]=true;}
 void makeGrid (int w) { // make a 2D grid of vertices
  for (int i=0; i<w; i++) {for (int j=0; j<w; j++) { G[w*i+j].setTo(height*.8*j/(w-1)+height/10,height*.8*i/(w-1)+height/10,0);}}    
  for (int i=0; i<w-1; i++) {for (int j=0; j<w-1; j++) {                  // define the triangles for the grid
    V[(i*(w-1)+j)*6]=i*w+j;       V[(i*(w-1)+j)*6+2]=(i+1)*w+j;       V[(i*(w-1)+j)*6+1]=(i+1)*w+j+1;
    V[(i*(w-1)+j)*6+3]=i*w+j;     V[(i*(w-1)+j)*6+5]=(i+1)*w+j+1;     V[(i*(w-1)+j)*6+4]=i*w+j+1;}; };
  nv = w*w;
  nt = 2*(w-1)*(w-1); 
  nc=3*nt;  }
 void update() {computeO(); normals(); }
  // ============================================= CORNER OPERATORS =======================================
 int nc = 0;                                // current number of corners (3 per triangle)
 int c = 0;                                 // current corner shown in image and manipulated with keys: n, p, o, l, r
 int sc=0;                                  // saved value of c
 int[] V = new int [3*maxnt];               // V table (triangle/vertex indices)
 int[] O = new int [3*maxnt];               // O table (opposite corner indices)
 int[] Tc = new int[3*maxnt];               // corner type

// operations on a corner
int t (int c) {return int(c/3);};          // triangle of corner    
int n (int c) {return 3*t(c)+(c+1)%3;};   // next corner in the same t(c)    
int p (int c) {return n(n(c));};  // previous corner in the same t(c)  
int v (int c) {return V[c] ;};   // id of the vertex of c             
pt g (int c) {return G[v(c)];};  // shortcut to get the point of the vertex v(c) of corner c
boolean b (int c) {return O[c]==-1;};       // if faces a border (has no opposite)
int o (int c) {if (b(c)) return c; else return O[c];}; // opposite (or self if it has no opposite)
int l (int c) {return o(n(c));}; // left neighbor (or next if n(c) has no opposite)                      
int r (int c) {return o(p(c));}; // right neighbor (or previous if p(c) has no opposite)                    
int s (int c) {return n(l(c));}; // swings around v(c) or around a border loop

// operations on the selected corner c
int t() {return t(c);}
int n() {return n(c);}
int p() {return p(c);}
 int v() {return v(c);}
int o() {return o(c);}
boolean b() {return b(c);}             // border: returns true if corner has no opposite
int l() {return l(c);}
int r() {return r(c);}
int s() {return s(c);}
pt g() {return g(c);}            // shortcut to get the point of the vertex v(c) of corner c

vec Nv (int c) {return(Nv[V[c]]);}; vec Nv() {return Nv(c);}            // shortcut to get the normal of v(c) 
vec Nt (int c) {return(Nt[t(c)]);}; vec Nt() {return Nt(c);}            // shortcut to get the normal of t(c) 
int w (int c) {return(W[c]);};               // temporary indices to mid-edge vertices associated with corners during subdivision
boolean vis(int c) {return visible[t(c)]; };   // true if tiangle of c is visible
  
void previous() {c=p(c);};
void next() {c=n(c); println("...... next");};
void back() {if(!b(c)) {c=o(c);};};
void left() {next(); back();};
void right() {previous(); back();};
void swing() {left(); next(); };

void writeCorner (int c) {println("c="+c+", n="+n(c)+", p="+p(c)+", o="+o(c)+", v="+v(c)+", t="+t(c)+", EB symbol="+triangleSymbol[t(c)]+"."+", nt="+nt+", nv="+nv ); }; 
void writeCorner () {writeCorner (c);}
void writeCorners () {for (int c=0; c<nc; c++) {println("T["+c+"]="+t(c)+", visible="+visible[t(c)]+", v="+v(c)+",  o="+o(c));};}

pt cg(int c) {pt cPt = midPt(g(c),midPt(g(c),triCenter(t(c))));  return(cPt); };   // computes point at corner
pt corner(int c) {return midPt(g(c),triCenter(t(c)));   };   // returns corner point
void showCorner(int c, int r) {pt cPt = midPt(g(c),midPt(g(c),corner(c)));  cPt.show(r); };   // renders corner c as small ball

// ============================================= O TABLE CONSTRUCTION =========================================
void computeOnaive() {                         // sets the O table from the V table, assumes consistent orientation of triangles
  for (int i=0; i<3*nt; i++) {O[i]=-1;};  // init O table to -1: has no opposite (i.e. is a border corner)
  for (int i=0; i<nc; i++) {  for (int j=i+1; j<nc; j++) {       // for each corner i, for each other corner j
      if( (v(n(i))==v(p(j))) && (v(p(i))==v(n(j))) ) {O[i]=j; O[j]=i;};};};}// make i and j opposite if they match         

void computeO() { 
  int val[] = new int [nv]; for (int v=0; v<nv; v++) val[v]=0;  for (int c=0; c<nc; c++) val[v(c)]++;   //  valences
  int fic[] = new int [nv]; int rfic=0; for (int v=0; v<nv; v++) {fic[v]=rfic; rfic+=val[v];};  // head of list of incident corners
  for (int v=0; v<nv; v++) val[v]=0;   // valences wil be reused to track how many incident corners were encountered for each vertex
  int [] C = new int [nc]; for (int c=0; c<nc; c++) C[fic[v(c)]+val[v(c)]++]=c;  // vor each vertex: the list of val[v] incident corners starts at C[fic[v]]
  for (int c=0; c<nc; c++) O[c]=-1;    // init O table to -1 meaning that a corner has no opposite (i.e. faces a border)
  for (int v=0; v<nv; v++)             // for each vertex...
     for (int a=fic[v]; a<fic[v]+val[v]-1; a++) for (int b=a+1; b<fic[v]+val[v]; b++)  { // for each pair (C[a],C[b[]) of its incident corners
        if (v(n(C[a]))==v(p(C[b]))) {O[p(C[a])]=n(C[b]); O[n(C[b])]=p(C[a]); }; // if C[a] follows C[b] around v, then p(C[a]) and n(C[b]) are opposite
        if (v(n(C[b]))==v(p(C[a]))) {O[p(C[b])]=n(C[a]); O[n(C[a])]=p(C[b]); };        };                }
    
// ============================================= DISPLAY =======================================
pt Cbox = new pt(width/2,height/2,0);                   // mini-max box center
float Rbox=1000;                                        // Radius of enclosing ball
boolean showLabels=false; 
void computeBox() {
  pt Lbox =  G[0].make();  pt Hbox =  G[0].make();
  for (int i=1; i<nv; i++) { 
    Lbox.x=min(Lbox.x,G[i].x); Lbox.y=min(Lbox.y,G[i].y); Lbox.z=min(Lbox.z,G[i].z);
    Hbox.x=max(Hbox.x,G[i].x); Hbox.y=max(Hbox.y,G[i].y); Hbox.z=max(Hbox.z,G[i].z); 
    };
  Cbox.setToPoint(midPt(Lbox,Hbox));  Rbox=Cbox.disTo(Hbox);
  };
void show() {
  int col=60;
  noSmooth(); noStroke();
  if(showDistance) showDistance(); else if(showEB) showEB();  else if(showTriangles) showTriangles();  
  if (showEdges) {stroke(dblue); for(int i=0; i<nc; i++) if(visible[t(i)]) drawEdge(i); };  
  if (showSelectedTriangle) {noStroke(); fill(green); shade(t(c)); noFill(); }; 
  stroke(red); showBorder();
  if (showVertices) {noStroke(); noSmooth();fill(white); for (int v=0; v<nv; v++)  G[v].show(r); noFill();};
  if (showNormals) {stroke(blue); showTriNormals(); stroke(magenta); showVertexNormals(); };                // show triangle normals
  if (showLabels) { fill(black); 
      for (int i=0; i<nv; i++) {G[i].label("v"+str(i),labelD); }; 
      for (int i=0; i<nc; i++) {corner(i).label("c"+str(i),labelD); }; 
      for (int i=0; i<nt; i++) {triCenter(i).label("t"+str(i),labelD); }; noFill();};
  noStroke(); fill(dred); showCorner(prevc,r); fill(dgreen); mark.show(int(1.5*r)); fill(dblue); showCorner(c,int(2*r));  
  }
//  ==========================================================  EDGES ===========================================
boolean showEdges=false;
void findShortestEdge() {c=cornerOfShortestEdge();  } 
int cornerOfShortestEdge() {  // assumes manifold
  float md=d(g(p(0)),g(n(0))); int ma=0;
  for (int a=1; a<nc; a++) if (vis(a)&&(d(g(p(a)),g(n(a)))<md)) {ma=a; md=d(g(p(a)),g(n(a)));}; 
  return ma;
  } 
void drawEdge(int c) {showLine(g(p(c)),g(n(c))); };  // draws edge of t(c) opposite to corner c
void showBorder() {for (int i=0; i<nc; i++) {if (visible[t(i)]&&b(i)) {drawEdge(i);}; }; };         // draws all border edges

//  ==========================================================  TRIANGLES ===========================================
 boolean showTriangles=true;
 boolean showSelectedTriangle=false;
 int nt = 0;                   // current number of triangles
 void addTriangle(int i, int j, int k) {V[nc++]=i; V[nc++]=j; V[nc++]=k; visible[nt++]=true;}
 boolean[] visible = new boolean[maxnt];    // set if triangle visible
 int[] Mt = new int[maxnt];                 // triangle markers for distance and other things   
 boolean [] VisitedT = new boolean [maxnt];  // triangle visited
 pt triCenter(int i) {return(triCenterFromPts( G[V[3*i]], G[V[3*i+1]], G[V[3*i+2]] )); };  pt triCenter() {return triCenter(t());}  // computes center of triangle t(i) 
 void writeTri (int i) {println("T"+i+": V = ("+V[3*i]+":"+v(o(3*i))+","+V[3*i+1]+":"+v(o(3*i+1))+","+V[3*i+2]+":"+v(o(3*i+2))+")"); };
 void hitTriangle() {
  prevc=c;       // save c for geodesic and other applications
  float smallestDepth=10000000;
  boolean hit=false;
  for (int t=0; t<nt; t++) {
    if (rayHitTri(eye,mark,g(3*t),g(3*t+1),g(3*t+2))) {hit=true;
      float depth = rayDistTriPlane(eye,mark,g(3*t),g(3*t+1),g(3*t+2));
      if ((depth>0)&&(depth<smallestDepth)) {smallestDepth=depth;  c=3*t;};
      }; 
    };
  if (hit) {        // sets c to be the closest corner in t(c) to the picked point
    pt X = eye.make(); X.addScaledVec(smallestDepth,eye.vecTo(mark));
    mark.setToPoint(X);
    float distance=X.disTo(g(c));
    int b=c;
    if (X.disTo(g(n(c)))<distance) {b=n(c); distance=X.disTo(g(b)); };
    if (X.disTo(g(p(c)))<distance) {b=p(c);};
    c=b;
    println("c="+c+", pc="+prevc+", t(pc)="+t(prevc));
    };
  }
 void shade(int t) {if(visible[t]) { beginShape(TRIANGLES); g(3*t).vert(); g(3*t+1).vert(); g(3*t+2).vert();  endShape(); };}; // shade tris
 void showTriangles() {fill(cyan); for(int t=0; t<nt; t++)  shade(t); noFill();}; 
//  ==========================================================  VERTICES ===========================================
 boolean showVertices=false;
 int nv = 0;                              // current  number of vertices
 pt[] G = new pt [maxnv];                   // geometry table (vertices)
 int[] Mv = new int[maxnv];                  // vertex markers
 int [] Valence = new int [maxnv];          // vertex valence (count of incident triangles)
 boolean [] Border = new boolean [maxnv];   // vertex is border
 boolean [] VisitedV = new boolean [maxnv];  // vertex visited
 int r=5;                                // radius of spheres for displaying vertices
int addVertex(pt P) { G[nv].setTo(P); nv++; return nv-1;};
int addVertex(float x, float y, float z) { G[nv].x=x; G[nv].y=y; G[nv].z=z; nv++; return nv-1;};
void move(int c) {g(c).addScaledVec(pmouseY-mouseY,Nv(c));}
void move(int c, float d) {g(c).addScaledVec(d,Nv(c));}
void move() {move(c); normals();}
void moveROI() {
     pt Q = new pt(0,0,0);
     for (int i=0; i<nv; i++) Mv[i]=0;  // resets the valences to 0
     computeDistance(5);
     for (int i=0; i<nv; i++) VisitedV[i]=false;  // resets the valences to 0
     computeTriNormals(); computeVertexNormals();
     for (int i=0; i<nc; i++) if(!VisitedV[v(i)]&&(Mv[v(i)]!=0)) move(i,1.*(pmouseY-mouseY+mouseX-pmouseX)*(rings-Mv[v(i)])/rings/10);  // moves ROI
     computeDistance(7);
     Q.setTo(g());
     smoothROI();
     g().setTo(Q);
     }
     
//  ==========================================================  NORMALS ===========================================
boolean showNormals=false;
vec[] Nv = new vec [maxnv];                 // vertex normals or laplace vectors
vec[] Nt = new vec [maxnt];                // triangles normals
void normals() {computeValenceAndResetNormals(); computeTriNormals(); computeVertexNormals(); }
void computeValenceAndResetNormals() {      // caches valence of each vertex
  for (int i=0; i<nv; i++) {Nv[i].setTo(0,0,0); Valence[i]=0;};  // resets the valences to 0
  for (int i=0; i<nc; i++) {Valence[v(i)]++; };
  }
vec triNormal(int t) { return C(V(g(3*t),g(3*t+1)),V(g(3*t),g(3*t+2))); };  
vec triNormal() {return triNormal(t());} // computes triangle t(i) normal * area / 2
void computeTriNormals() {for (int i=0; i<nt; i++) {Nt[i].setToVec(triNormal(i)); }; };             // caches normals of all tirangles
void computeVertexNormals() {  // computes the vertex normals as sums of the normal vectors of incident tirangles scaled by area/2
  for (int i=0; i<nv; i++) {Nv[i].setTo(0,0,0);};  // resets the valences to 0
  for (int i=0; i<nc; i++) {Nv[v(i)].add(Nt[t(i)]);};
  for (int i=0; i<nv; i++) {Nv[i].makeUnit();};            };
void showCornerNormal(int c) {S(20*r,Nt[t(c)]).show(M(g(c),g(c),triCenter(t(c))));};   // renders corner normal
void showVertexNormals() {for (int i=0; i<nv; i++) S(10*r,Nv[i]).show(G[i]);  };
void showTriNormals() {for (int i=0; i<nt; i++) S(10*r,U(Nt[i])).show(triCenter(i));  };

// ============================================================= SMOOTHING ============================================================
void computeLaplaceVectors() {  // computes the vertex normals as sums of the normal vectors of incident tirangles scaled by area/2
  computeValenceAndResetNormals();
  for (int i=0; i<3*nt; i++) {Nv[v(p(i))].add(g(p(i)).vecTo(g(n(i))));};
  for (int i=0; i<nv; i++) {Nv[i].div(Valence[i]);};                         };
void tuck(float s) {for (int i=0; i<nv; i++) {G[i].addScaledVec(s,Nv[i]);}; };  // displaces each vertex by a fraction s of its normal
void smoothen() {normals(); computeLaplaceVectors(); tuck(0.6); computeLaplaceVectors(); tuck(-0.6);};
void tuckROI(float s) {for (int i=0; i<nv; i++) if (Mv[i]!=0) G[i].addScaledVec(s,Nv[i]); };  // displaces each vertex by a fraction s of its normal
void smoothROI() {computeLaplaceVectors(); tuckROI(0.5); computeLaplaceVectors(); tuckROI(-0.5);};
// ============================================================= SUBDIVISION ============================================================
int[] W = new int [3*maxnt];               // mid-edge vertex indices for subdivision (associated with corner opposite to edge)
void splitEdges() {            // creates a new vertex for each edge and stores its ID in the W of the corner (and of its opposite if any)
  for (int i=0; i<3*nt; i++) {  // for each corner i
    if(b(i)) {G[nv]=midPt(g(n(i)),g(p(i))); W[i]=nv++;}
    else {if(i<o(i)) {G[nv]=midPt(g(n(i)),g(p(i))); W[o(i)]=nv; W[i]=nv++; }; }; }; } // if this corner is the first to see the edge
  
void bulge() {              // tweaks the new mid-edge vertices according to the Butterfly mask
  for (int i=0; i<3*nt; i++) {
    if((!b(i))&&(i<o(i))) {    // no tweak for mid-vertices of border edges
     if (!b(p(i))&&!b(n(i))&&!b(p(o(i)))&&!b(n(o(i))))
      {G[W[i]].addScaledVec(0.25,midPt(midPt(g(l(i)),g(r(i))),midPt(g(l(o(i))),g(r(o(i))))).vecTo(midPt(g(i),g(o(i))))); }; }; }; };
  
void splitTriangles() {    // splits each tirangle into 4
  for (int i=0; i<3*nt; i=i+3) {
    V[3*nt+i]=v(i); V[n(3*nt+i)]=w(p(i)); V[p(3*nt+i)]=w(n(i));
    V[6*nt+i]=v(n(i)); V[n(6*nt+i)]=w(i); V[p(6*nt+i)]=w(p(i));
    V[9*nt+i]=v(p(i)); V[n(9*nt+i)]=w(n(i)); V[p(9*nt+i)]=w(i);
    V[i]=w(i); V[n(i)]=w(n(i)); V[p(i)]=w(p(i));
    };
  nt=4*nt; nc=3*nt;  };
  
void refine() {update(); splitEdges(); bulge(); splitTriangles(); update();}
  
//  ========================================================== FILL HOLES ===========================================
void fanHoles() {for (int cc=0; cc<nc; cc++) if (visible[t(cc)]&&b(cc)) fanThisHole(cc); normals();  }
void fanThisHole() {fanThisHole(c);}
void fanThisHole(int cc) {   // fill shole with triangle fan (around average of parallelogram predictors). Must then call computeO to restore O table
 if(!b(cc)) return ; // stop if cc is not facing a border
 G[nv].setTo(0,0,0);   // tip vertex of fan
 int o=0;              // tip corner of new fan triangle
 int n=0;              // triangle count in fan
 int a=n(cc);          // corner running along the border
 while (n(a)!=cc) {    // walk around the border loop 
   if(b(p(a))) {       // when a is at the left-end of a border edge
      G[nv].addPt( M(M(g(a),g(n(a))),S(g(a),V(g(p(a)),g(n(a))))) ); // add parallelogram prediction and mid-edge point
      o=3*nt; V[o]=nv; V[n(o)]=v(n(a)); V[p(o)]=v(a); visible[nt]=true; nt++; // add triangle to V table, make it visible
      O[o]=p(a); O[p(a)]=o;        // link opposites for tip corner
      O[n(o)]=-1; O[p(o)]=-1;
      n++;}; // increase triangle-count in fan
    a=s(a);} // next corner along border
 G[nv].mul(1./n); // divide fan tip to make it the average of all predictions
 a=o(cc);       // reset a to walk around the fan again and set up O
 int l=n(a);   // keep track of previous
 int i=0; 
 while(i<n) {a=s(a); if(v(a)==nv) { i++; O[p(a)]=l; O[l]=p(a); l=n(a);}; };  // set O around the fan
 nv++;  nc=3*nt;  // update vertex count and corner count
 };

// =========================================== GEODESIC MEASURES, DISTANCES =============================
 boolean  showPath=false, showDistance=false;  
 boolean[] P = new boolean [3*maxnt];       // marker of corners in a path to parent triangle
 int[] Distance = new int[maxnt];           // triangle markers for distance fields 
 int[] SMt = new int[maxnt];                // sum of triangle markers for isolation
 int prevc = 0;                             // previously selected corner
 int rings=2;                           // number of rings for colorcoding

void computeDistance(int maxr) {
  int tc=0;
  int r=1;
  for(int i=0; i<nt; i++) {Mt[i]=0;};  Mt[t(c)]=1; tc++;
  for(int i=0; i<nv; i++) {Mv[i]=0;};
  while ((tc<nt)&&(r<=maxr)) {
      for(int i=0; i<nc; i++) {if ((Mv[v(i)]==0)&&(Mt[t(i)]==r)) {Mv[v(i)]=r;};};
     for(int i=0; i<nc; i++) {if ((Mt[t(i)]==0)&&(Mv[v(i)]==r)) {Mt[t(i)]=r+1; tc++;};};
     r++;
     };
  rings=r;
  }
  
void computeIsolation() {
  println("Starting isolation computation for "+nt+" triangles");
  for(int i=0; i<nt; i++) {SMt[i]=0;}; 
  for(c=0; c<nc; c+=3) {println("  triangle "+t(c)+"/"+nt); computeDistance(1000); for(int j=0; j<nt; j++) {SMt[j]+=Mt[j];}; };
  int L=SMt[0], H=SMt[0];  for(int i=0; i<nt; i++) { H=max(H,SMt[i]); L=min(L,SMt[i]);}; if (H==L) {H++;};
  c=0; for(int i=0; i<nt; i++) {Mt[i]=(SMt[i]-L)*255/(H-L); if(Mt[i]>Mt[t(c)]) {c=3*i;};}; rings=255;
  for(int i=0; i<nv; i++) {Mv[i]=0;};  for(int i=0; i<nc; i++) {Mv[v(i)]=max(Mv[v(i)],Mt[t(i)]);};
  println("finished isolation");
  }
  
void computePath() {                 // graph based shortest path between t(c0 and t(prevc), prevc is the previously picekd corner
  for(int i=0; i<nt; i++) {Mt[i]=0;}; Mt[t(prevc)]=1; // Mt[0]=1;
  for(int i=0; i<nc; i++) {P[i]=false;};
  int r=1;
  boolean searching=true;
  while (searching) {
     for(int i=0; i<nc; i++) {
       if (searching&&(Mt[t(i)]==0)&&(o(i)!=-1)) {
         if(Mt[t(o(i))]==r) {
           Mt[t(i)]=r+1; 
           P[i]=true; 
           if(t(i)==t(c)){searching=false;};
           };
         };
       };
     r++;
     };
  for(int i=0; i<nt; i++) {Mt[i]=0;};  // graph distance between triangle and t(c)
  rings=1;      // track ring number
  int b=c;
  int k=0;
   while (t(b)!=t(prevc)) {rings++;  
   if (P[b]) {b=o(b); print(".o");} else {if (P[p(b)]) {b=r(b);print(".r");} else {b=l(b);print(".l");};}; Mt[t(b)]=rings; };
  }
 void  showDistance() { for(int t=0; t<nt; t++) {if(Mt[t]==0) fill(cyan); else fill(ramp(Mt[t],rings)); shade(t);}; } 

//  ==========================================================  DELETE ===========================================
void hideROI() { for(int i=0; i<nt; i++) if(Mt[i]>0) visible[i]=false; }

//  ==========================================================  GARBAGE COLLECTION ===========================================
void clean() {excludeInvisibleTriangles();  compactVO(); compactV(); M.normals();}  // removes deleted triangles and unused vertices
void excludeInvisibleTriangles () {for (int b=0; b<nc; b++) {if (!visible[t(o(b))]) {O[b]=-1;};};}
void compactVO() {  
  int[] U = new int [nc];
  int lc=-1; for (int c=0; c<nc; c++) {if (visible[t(c)]) {U[c]=++lc; }; };
  for (int c=0; c<nc; c++) {if (!b(c)) {O[c]=U[o(c)];} else {O[c]=-1;}; };
  int lt=0;
  for (int t=0; t<nt; t++) {
    if (visible[t]) {
      V[3*lt]=V[3*t]; V[3*lt+1]=V[3*t+1]; V[3*lt+2]=V[3*t+2]; 
      O[3*lt]=O[3*t]; O[3*lt+1]=O[3*t+1]; O[3*lt+2]=O[3*t+2]; 
      visible[lt]=true; 
      lt++;
      };
    };
  nt=lt; nc=3*nt;    
  println("      ...  NOW: nv="+nv +", nt="+nt +", nc="+nc );
  }

void compactV() {  
  println("COMPACT VERTICES: nv="+nv +", nt="+nt +", nc="+nc );
  int[] U = new int [nv];
  boolean[] deleted = new boolean [nv];
  for (int v=0; v<nv; v++) {deleted[v]=true;};
  for (int c=0; c<nc; c++) {deleted[v(c)]=false;};
  int lv=-1; for (int v=0; v<nv; v++) {if (!deleted[v]) {U[v]=++lv; }; };
  for (int c=0; c<nc; c++) {V[c]=U[v(c)]; };
  lv=0;
  for (int v=0; v<nv; v++) {
    if (!deleted[v]) {G[lv].setToPoint(G[v]);  deleted[lv]=false; 
      lv++;
      };
    };
 nv=lv;
 println("      ...  NOW: nv="+nv +", nt="+nt +", nc="+nc );
  }

// ============================================================= ARCHIVAL ============================================================
boolean flipOrientation=false;            // if set, save will flip all triangles

void saveMesh() {
  String [] inppts = new String [nv+1+nt+1];
  int s=0;
  inppts[s++]=str(nv);
  for (int i=0; i<nv; i++) {inppts[s++]=str(G[i].x)+","+str(G[i].y)+","+str(G[i].z);};
  inppts[s++]=str(nt);
  if (flipOrientation) {for (int i=0; i<nt; i++) {inppts[s++]=str(V[3*i])+","+str(V[3*i+2])+","+str(V[3*i+1]);};}
    else {for (int i=0; i<nt; i++) {inppts[s++]=str(V[3*i])+","+str(V[3*i+1])+","+str(V[3*i+2]);};};
  saveStrings("mesh.vts",inppts);  println("saved on file");
  };

void loadMesh() {
  println("loading fn["+fni+"]: "+fn[fni]); 
  String [] ss = loadStrings(fn[fni]);
  String subpts;
  int s=0;   int comma1, comma2;   float x, y, z;   int a, b, c;
  nv = int(ss[s++]);
    print("nv="+nv);
    for(int k=0; k<nv; k++) {int i=k+s; 
      comma1=ss[i].indexOf(',');   
      x=float(ss[i].substring(0, comma1));
      String rest = ss[i].substring(comma1+1, ss[i].length());
      comma2=rest.indexOf(',');    y=float(rest.substring(0, comma2)); z=float(rest.substring(comma2+1, rest.length()));
      G[k].setTo(x,y,z);
    };
  s=nv+1;
  nt = int(ss[s]); nc=3*nt;
  println(", nt="+nt);
  s++;
  for(int k=0; k<nt; k++) {int i=k+s;
      comma1=ss[i].indexOf(',');   a=int(ss[i].substring(0, comma1));  
      String rest = ss[i].substring(comma1+1, ss[i].length()); comma2=rest.indexOf(',');  
      b=int(rest.substring(0, comma2)); c=int(rest.substring(comma2+1, rest.length()));
      V[3*k]=a;  V[3*k+1]=b;  V[3*k+2]=c;
    }
  }; 

//  ==========================================================  FLIP ===========================================
void flipWhenLonger() {for (int c=0; c<nc; c++) if (d(g(n(c)),g(p(c)))>d(g(c),g(o(c)))) flip(c); } 
void flip() {flip(c);}
void flip(int c) {      // flip edge opposite to corner c, FIX border cases
  if (b(c)) return;
    V[n(o(c))]=v(c); V[n(c)]=v(o(c));
    int co=o(c); O[co]=r(c); if(!b(p(c))) O[r(c)]=co; if(!b(p(co))) O[c]=r(co); if(!b(p(co))) O[r(co)]=c; O[p(c)]=p(co); O[p(co)]=p(c);  }
 
//  ==========================================================  SIMPLIFICATION  ===========================================
void collapse() {collapse(c);}
void collapse(int c) {if (b(c)) return;      // collapse edge opposite to corner c, does not check anything !!! assumes manifold
   int b=n(c), oc=o(c), vpc=v(p(c));
   visible[t(c)]=false; visible[t(oc)]=false;
   for (int a=b; a!=p(oc); a=n(l(a))) V[a]=vpc;
   O[l(c)]=r(c); O[r(c)]=l(c); O[l(oc)]=r(oc); O[r(oc)]=l(oc);  }

// ============================================================= COMPRESSION ============================================================
 boolean showEB=false, showEBrec=false;
 char[] triangleSymbol = new char[maxnt];
 char[] CLERS = new char[maxnt];
 int symbols=0;
 int stack[] = new int[10000];
 int stackHeight=1;
 int Ccount=0, Lcount=0, Ecount=0, Rcount=0, Scount=0;
 boolean EBisDone;
 int firstCorner=0; 
 int step=1;                              // to do something step by step

 void showEB() {
      for(int t=0; t<nt; t++) {fill(cyan);
         if (triangleSymbol[t]=='w') {fill(white);};
         if (triangleSymbol[t]=='B') {fill(black);};
         if (triangleSymbol[t]=='C') {fill(yellow);};
         if (triangleSymbol[t]=='L') {fill(blue);};
         if (triangleSymbol[t]=='E') {fill(magenta);};
         if (triangleSymbol[t]=='R') {fill(orange);};
         if (triangleSymbol[t]=='S') {fill(red);};
         shade(t); 
         }
      }  
 
void EBcompress(int c) {
 Ccount=0; Lcount=0; Ecount=0; Rcount=0; Scount=0; 
 resetStack(); 
 for (int v=0; v<nv; v++) {VisitedV[v]=false;};
 for (int t=0; t<nt; t++) {VisitedT[t]=false;};
 VisitedT[t(c)]=true; triangleSymbol[t(c)]='B'; VisitedV[v(c)]=true; VisitedV[v(n(c))]=true; VisitedV[v(p(c))]=true; c=r(c);
 symbols=0; 
 boolean EBisDone=false;
 while (!EBisDone) {
  VisitedT[t(c)]=true; 
  if (!VisitedV[v(c)]) {triangleSymbol[t(c)]='C'; Ccount++; CLERS[symbols++]=triangleSymbol[t(c)]; VisitedV[v(c)]=true; c=r(c); }
  else {
    if (VisitedT[t(r(c))]) {
        if (VisitedT[t(l(c))]) {triangleSymbol[t(c)]='E'; Ecount++; CLERS[symbols++]=triangleSymbol[t(c)]; c=stack[--stackHeight]; if (stackHeight==0) {EBisDone=true;};}
        else {triangleSymbol[t(c)]='R'; Rcount++; CLERS[symbols++]=triangleSymbol[t(c)]; c=l(c);};
       }
    else {
        if (VisitedT[t(l(c))]) {triangleSymbol[t(c)]='L'; Lcount++; CLERS[symbols++]=triangleSymbol[t(c)]; c=r(c);}
        else {triangleSymbol[t(c)]='S'; triangleSymbol[t(l(c))]='w'; Scount++; CLERS[symbols++]=triangleSymbol[t(c)]; stack[stackHeight++]=l(c); c=r(c);};
      };
    };
  }; 
  int total=Ccount+Lcount+Ecount+Rcount+Scount;
  println(nt+" triangles, "+total+" symbols: C="+Ccount+", L="+Lcount+", E="+Ecount+", R="+Rcount+", S="+Scount);
 }

int pop() {if (stackHeight==0){ println("Stack is empty"); stackHeight=1;}; return(stack[--stackHeight]);}
void push(int c) {stack[stackHeight++]=c; }
void resetStack() {stackHeight=1;};

void EBinit() {
   for (int v=0; v<nv; v++) {VisitedV[v]=false;};
   for (int t=0; t<nt; t++) {VisitedT[t]=false;};
   VisitedT[t(c)]=true; triangleSymbol[t(c)]='B'; VisitedV[v(c)]=true; VisitedV[v(n(c))]=true; VisitedV[v(p(c))]=true; c=r(c);
   symbols=0; EBisDone=false;
   }
   
void EBmove() {
 if (!EBisDone) {
  VisitedT[t(c)]=true; 
  if (!VisitedV[v(c)]) {triangleSymbol[t(c)]='C'; Ccount++; CLERS[symbols++]=triangleSymbol[t(c)]; VisitedV[v(c)]=true; c=r(c); }
  else {
    if (VisitedT[t(r(c))]) {
        if (VisitedT[t(l(c))]) {triangleSymbol[t(c)]='E'; Ecount++; CLERS[symbols++]=triangleSymbol[t(c)]; c=stack[--stackHeight]; if (stackHeight==0) {EBisDone=true;};}
        else {triangleSymbol[t(c)]='R'; Rcount++; CLERS[symbols++]=triangleSymbol[t(c)]; c=l(c);};
       }
    else {
        if (VisitedT[t(l(c))]) {triangleSymbol[t(c)]='L'; Lcount++; CLERS[symbols++]=triangleSymbol[t(c)]; c=r(c);}
        else {triangleSymbol[t(c)]='S'; triangleSymbol[t(l(c))]='w'; Scount++; CLERS[symbols++]=triangleSymbol[t(c)]; stack[stackHeight++]=l(c); c=r(c);};
      };
    };
   print(symbols+":"+CLERS[symbols-1]+" ");
  } else {print(".");};
 }
 
void EBjump() {
  int t=t(c);
  if (triangleSymbol[t]=='B') {c=r(c);};
  if (triangleSymbol[t]=='C') {c=r(c);};
  if (triangleSymbol[t]=='L') {c=r(c);};
  if (triangleSymbol[t]=='E') {c=pop();};
  if (triangleSymbol[t]=='R') {c=l(c);};
  if (triangleSymbol[t]=='S') {push(l(c)); c=r(c);};
  }

void EBshow(int c, pt nV, pt pV) {
  fill(yellow);
  int t=t(c);
  pt tV = g(c).make();
  if (triangleSymbol[t]=='B') {fill(200,200,200);tV.moveTowards(0.07,nV);};
  if (triangleSymbol[t]=='C') {fill(90,250,200); tV.moveTowards(0.07,nV);};
  if (triangleSymbol[t]=='L') {fill(20,250,250);};
  if (triangleSymbol[t]=='E') {fill(155,250,150); tV.moveTowards(0.05,pV); tV.moveTowards(0.05,nV);};
  if (triangleSymbol[t]=='R') {fill(127,250,200);};
  if (triangleSymbol[t]=='S') {fill(255,250,150); tV.moveTowards(0.05,pV); tV.moveTowards(0.05,nV);};
  beginShape(TRIANGLES);  nV.vert();   pV.vert();  tV.vert(); endShape(); 
  if (triangleSymbol[t]=='B') {EBshow(r(c),nV,tV);};
  if (triangleSymbol[t]=='C') {EBshow(r(c),nV,tV);};
  if (triangleSymbol[t]=='L') { EBshow(r(c),nV,tV);};
  if (triangleSymbol[t]=='E') { };
  if (triangleSymbol[t]=='R') { EBshow(l(c),tV,pV);};
  if (triangleSymbol[t]=='S') { EBshow(r(c),nV,tV); EBshow(l(c),tV,pV);};
  };

void EBprint(int c) {
   int t=t(c);
   print(triangleSymbol[t]); CLERS[symbols++]=triangleSymbol[t(c)]; 
  if (triangleSymbol[t]=='B') {EBprint(r(c));};
  if (triangleSymbol[t]=='C') {EBprint(r(c));};
  if (triangleSymbol[t]=='L') {EBprint(r(c));};
  if (triangleSymbol[t]=='E') { };
  if (triangleSymbol[t]=='R') {EBprint(l(c));};
  if (triangleSymbol[t]=='S') {EBprint(r(c)); EBprint(l(c));};
  };

void EBprintS(int pc) {
 int c=pc; 
 symbols=0;
 resetStack();
 boolean EBisDone=false;
 while (!EBisDone) {
   int t=t(c);
//   print(triangleSymbol[t]); 
   CLERS[symbols++]=triangleSymbol[t(c)]; 
  if (triangleSymbol[t]=='B') {c=r(c);};
  if (triangleSymbol[t]=='C') {c=r(c);};
  if (triangleSymbol[t]=='L') {c=r(c);};
  if (triangleSymbol[t]=='E') {c=pop(); if (stackHeight==0) {EBisDone=true;}};
  if (triangleSymbol[t]=='R') {c=l(c);};
  if (triangleSymbol[t]=='S') {push(r(c)); c=l(c);};
   };
 };

int leadingCS() { int r = 1; while (CLERS[r]=='C') {r++;};  return(r);};

void EBstats(int lCs) {
 int cc=0, cl=0, ce=0, cr=0, cs=0, ct=0; 
 int lc=0, ll=0, le=0, lr=0, ls=0, lt=0; 
 int ec=0, el=0, ee=0, er=0, es=0, et=0; 
 int rc=0, rl=0, re=0, rr=0, rs=0, rt=0; 
 int sc=0, sl=0, se=0, sr=0, ss=0, st=0; 
 char last='C';
  println("    The "+lCs+" leading Cs are not counted and replaced by an overhead of "+int(log2(lCs))+" bits");
 for (int i=lCs; i<symbols; i++) {
   char s=CLERS[i];    print(s);
   if (last=='C') {if(s=='C') {cc++;}; if(s=='L') {cl++;}; if(s=='E') {ce++;}; if(s=='R') {cr++;}; if(s=='S') {cs++;}; };
   if (last=='L') {if(s=='C') {lc++;}; if(s=='L') {ll++;}; if(s=='E') {le++;}; if(s=='R') {lr++;}; if(s=='S') {ls++;}; };
   if (last=='E') {if(s=='C') {ec++;}; if(s=='L') {el++;}; if(s=='E') {ee++;}; if(s=='R') {er++;}; if(s=='S') {es++;}; };
   if (last=='R') {if(s=='C') {rc++;}; if(s=='L') {rl++;}; if(s=='E') {re++;}; if(s=='R') {rr++;}; if(s=='S') {rs++;}; };
   if (last=='S') {if(s=='C') {sc++;}; if(s=='L') {sl++;}; if(s=='E') {se++;}; if(s=='R') {sr++;}; if(s=='S') {ss++;}; };
   last=s;
   };
  println();
  print("symbols reduced from "+symbols);  int rsymbols=symbols-lCs;  println(" to "+rsymbols);
  ct=cc+lc+ec+rc+sc;
  lt=cl+ll+el+rl+sl;
  et=ce+le+ee+re+se;
  rt=cr+lr+er+rr+sr;
  st=cs+ls+es+rs+ss;
  
  float Cf=float(ct)/rsymbols, Lf=float(lt)/rsymbols, Ef=float(et)/rsymbols, Rf=float(rt)/rsymbols, Sf=float(st)/rsymbols;
  float entropy = -( log2(Cf)*Cf + log2(Lf)*Lf + log2(Ef)*Ef + log2(Rf)*Rf + log2(Sf)*Sf ); 
   println("100*Frequencies: C="+nf(Cf*100,2,2)+", L="+nf(Lf*100,2,2)+", E="+nf(Ef*100,2,2)+", R="+nf(Rf*100,2,2)+", S="+nf(Sf*100,2,2));
   println("***   Entropy (over remaining symbols ) = "+nf(entropy,1,2));
  println();
  println("COUNTS for "+rsymbols+" CLERS symbols:");
  println("        COUNTS cc="+nf(cc,4)+",  lc="+nf(lc,4)+",  ec="+nf(ec,4)+",  rc="+nf(rc,4)+",  sc="+nf(sc,4)+" .c="+nf(ct,4)); 
  println("        COUNTS cl="+nf(cl,4)+",  ll="+nf(ll,4)+",  el="+nf(el,4)+",  rl="+nf(rl,4)+",  sl="+nf(sl,4)+" .l="+nf(lt,4)); 
  println("        COUNTS ce="+nf(ce,4)+",  le="+nf(le,4)+",  ee="+nf(ee,4)+",  re="+nf(re,4)+",  se="+nf(se,4)+" .e="+nf(et,4)); 
  println("        COUNTS cr="+nf(cr,4)+",  lr="+nf(lr,4)+",  er="+nf(er,4)+",  rr="+nf(rr,4)+",  sr="+nf(sr,4) +" .r="+nf(rt,4)); 
  println("        COUNTS cs="+nf(cs,4)+",  ls="+nf(ls,4)+",  es="+nf(es,4)+",  rs="+nf(rs,4)+",  ss="+nf(ss,4) +" .s="+nf(st,4)); 
  float cost = entropy*rsymbols;   float costWlcs = cost+int(log2(lCs));
  float e = cost/(symbols);   float eWlcs = costWlcs/(symbols); 
  println("***  Amortized over all symbols :");
  println("*** No-context:                 Entropy = "+nf(e,1,2)+" bpt. Total cost = "+nf(cost,6,2)+" bits");
  println("*** counting RLE of leading Cs: Entropy = "+nf(eWlcs,1,2)+" bpt. Total cost = "+nf(costWlcs,6,2)+" bits");

  println("Pairs frequencies:");
  println("        COUNTS cc="+nf(float(cc)/rsymbols,1,4)+",  lc="+nf(float(lc)/rsymbols,1,4)+",  ec="+nf(float(ec)/rsymbols,1,4)+",  rc="+nf(float(rc)/rsymbols,1,4)+",  sc="+nf(float(sc)/rsymbols,1,4)+" .c="+nf(float(ct)/rsymbols,1,4)); 
  println("        COUNTS cl="+nf(float(cl)/rsymbols,1,4)+",  ll="+nf(float(ll)/rsymbols,1,4)+",  el="+nf(float(el)/rsymbols,1,4)+",  rl="+nf(float(rl)/rsymbols,1,4)+",  sl="+nf(float(sl)/rsymbols,1,4)+" .l="+nf(float(lt)/rsymbols,1,4)); 
  println("        COUNTS ce="+nf(float(ce)/rsymbols,1,4)+",  le="+nf(float(le)/rsymbols,1,4)+",  ee="+nf(float(ee)/rsymbols,1,4)+",  re="+nf(float(re)/rsymbols,1,4)+",  se="+nf(float(se)/rsymbols,1,4)+" .e="+nf(float(et)/rsymbols,1,4)); 
  println("        COUNTS cr="+nf(float(cr)/rsymbols,1,4)+",  lr="+nf(float(lr)/rsymbols,1,4)+",  er="+nf(float(er)/rsymbols,1,4)+",  rr="+nf(float(rr)/rsymbols,1,4)+",  sr="+nf(float(sr)/rsymbols,1,4) +" .r="+nf(float(rt)/rsymbols,1,4)); 
  println("        COUNTS cs="+nf(float(cs)/rsymbols,1,4)+",  ls="+nf(float(ls)/rsymbols,1,4)+",  es="+nf(float(es)/rsymbols,1,4)+",  rs="+nf(float(rs)/rsymbols,1,4)+",  ss="+nf(float(ss)/rsymbols,1,4) +" .s="+nf(float(st)/rsymbols,1,4)); 


  ct=cc+cl+ce+cr+cs;
  lt=lc+ll+le+lr+ls;
  et=ec+el+ee+er+es;
  rt=rc+rl+re+rr+rs;
  st=sc+sl+se+sr+ss;

  println();
  float ccf=0, clf=0, cef=0, crf=0, csf=0;
  float lcf=0, llf=0, lef=0, lrf=0, lsf=0;
  float ecf=0, elf=0, eef=0, erf=0, esf=0;
  float rcf=0, rlf=0, ref=0, rrf=0, rsf=0;
  float scf=0, slf=0, sef=0, srf=0, ssf=0;
  
  if (ct!=0) {  ccf=float(cc)/ct; clf=float(cl)/ct; cef=float(ce)/ct; crf=float(cr)/ct; csf=float(cs)/ct; };
  if (lt!=0) {  lcf=float(lc)/lt; llf=float(ll)/lt; lef=float(le)/lt; lrf=float(lr)/lt; lsf=float(ls)/lt; };
  if (et!=0) {  ecf=float(ec)/et; elf=float(el)/et; eef=float(ee)/et; erf=float(er)/et; esf=float(es)/et; };
  if (rt!=0) {  rcf=float(rc)/rt; rlf=float(rl)/rt; ref=float(re)/rt; rrf=float(rr)/rt; rsf=float(rs)/rt; };
  if (st!=0) {  scf=float(sc)/st; slf=float(sl)/st; sef=float(se)/st; srf=float(sr)/st; ssf=float(ss)/st; };
  
  println("  Context frequencies");
  println("        % cc="+nf(ccf,0,2)+",  lc="+nf(lcf,0,2)+",  ec="+nf(ecf,0,2)+",  rc="+nf(rcf,0,2)+",  sc="+nf(scf,0,2)); 
  println("        % cl="+nf(clf,0,2)+",  ll="+nf(llf,0,2)+",  el="+nf(elf,0,2)+",  rl="+nf(rlf,0,2)+",  sl="+nf(slf,0,2)); 
  println("        % ce="+nf(cef,0,2)+",  le="+nf(lef,0,2)+",  ee="+nf(eef,0,2)+",  re="+nf(ref,0,2)+",  se="+nf(sef,0,2)); 
  println("        % cr="+nf(crf,0,2)+",  lr="+nf(lrf,0,2)+",  er="+nf(erf,0,2)+",  rr="+nf(rrf,0,2)+",  sr="+nf(srf,0,2)); 
  println("        % cs="+nf(csf,0,2)+",  ls="+nf(lsf,0,2)+",  es="+nf(esf,0,2)+",  rs="+nf(rsf,0,2)+",  ss="+nf(ssf,0,2)); 
  println();
   
  float cE = -( log2(ccf)*ccf + log2(clf)*clf + log2(cef)*cef + log2(crf)*crf + log2(csf)*csf ) ; 
  float lE = -( log2(lcf)*lcf + log2(llf)*llf + log2(lef)*lef + log2(lrf)*lrf + log2(lsf)*lsf ) ; 
  float eE = -( log2(ecf)*ecf + log2(elf)*elf + log2(eef)*eef + log2(erf)*erf + log2(esf)*esf ) ; 
  float rE = -( log2(rcf)*rcf + log2(rlf)*rlf + log2(ref)*ref + log2(rrf)*rrf + log2(rsf)*rsf ) ; 
  float sE = -( log2(scf)*scf + log2(slf)*slf + log2(sef)*sef + log2(srf)*srf + log2(ssf)*ssf ) ; 
  
  println("    Stream entropies: after C="+nf(cE,1,2)+", after L="+nf(lE,1,2)+", after E="+nf(eE,1,2)+", after R="+nf(rE,1,2)+", after S="+nf(sE,1,2));
  println("    Frequencies:            C="+nf(Cf,1,2)+",       L="+nf(Lf,1,2)+",       E="+nf(Ef,1,2)+",       R="+nf(Rf,1,2)+",       S="+nf(Sf,1,2));
  float Centropy=cE*Cf+lE*Lf+eE*Ef+rE*Rf+sE*Sf;
  cost = Centropy*rsymbols;    costWlcs = cost+int(log2(lCs));
  e = cost/symbols;    eWlcs = costWlcs/symbols; 
  println("***   Entropy (over remaining symbols ) = "+nf(Centropy,1,2));
  println("***  Amortized over all symbols :");
  println("*** Average context Entropy = "+nf(Centropy,1,2)+" bpt. Total cost = "+nf(Centropy*symbols,6,2)+" bits");
  println("*** Ccontext:                   Entropy = "+nf(e,1,2)+" bpt. Total cost = "+nf(cost,6,2)+" bits");
  println("*** counting RLE of leading Cs: Entropy = "+nf(eWlcs,1,2)+" bpt. Total cost = "+nf(costWlcs,6,2)+" bits");
  println("+++++++++++++++++++++++++++++++++++++++++++++");
  }

  } // ==== END OF MESH CLASS
  
float log2(float x) {float r=0; if (x>0.00001) { r=log(x) / log(2);} ; return(r);}
vec labelD=new vec(-4,+4, 12);           // offset vector for drawing labels
int maxr=1;