import graph3;
size(400);
currentlight.background=palegreen;
settings.digits=15;

real c=(1+sqrt(5))/2;

triple[] z={(c,1,0),(-c,1,0),(-c,-1,0),(c,-1,0)};
triple[] x={(0,c,1),(0,-c,1),(0,-c,-1),(0,c,-1)};
triple[] y={(1,0,c),(1,0,-c),(-1,0,-c),(-1,0,c)};

triple[][] Q=
  {
   {z[0],y[1],x[3],x[0],y[0],z[3]},
   {z[1],x[0],x[3],y[2],z[2],y[3]},
   {z[2],z[1],y[2],x[2],x[1],y[3]},
   {z[3],z[0],y[0],x[1],x[2],y[1]},
   {x[0],x[3],z[1],y[3],y[0],z[0]},
   {x[1],x[2],z[2],y[3],y[0],z[3]},
   {x[2],x[1],z[3],y[1],y[2],z[2]},
   {x[3],x[0],z[0],y[1],y[2],z[1]},
   {y[0],y[3],x[1],z[3],z[0],x[0]},
   {y[1],y[2],x[2],z[3],z[0],x[3]},
   {y[2],y[1],x[3],z[1],z[2],x[2]},
   {y[3],y[0],x[0],z[1],z[2],x[1]}
  };

int nArc=4;

path3 p=Arc(O,Q[0][0],Q[0][1],nArc);
real R=abs(point(p,reltime(p,1/3)));

triple[][] P;
for(int i=0;i < Q.length;++i){
  P[i]=new triple[] ;
  for(int j=0;j < Q[i].length;++j){
    P[i][j]=Q[i][j]/R;
  }
}

// FIXME: Use a baryicentric coordinate mesh
surface sphericaltriangle(triple center, triple A, triple B, triple C,
                          int nu=3, int nv=nu) {
  path3 tri1=Arc(center,A,B,nArc);
  path3 tri2=Arc(center,A,C,nArc);
  path3 tri3=Arc(center,B,C,nArc);
  triple tri(pair p) {
    path3 cr=Arc(O,relpoint(tri2,p.x),relpoint(tri3,p.x),nArc);
    return relpoint(cr,p.y);
  };

  return surface(tri,(0,0),(1-sqrtEpsilon,1),nu,nv,Spline);
}

for(int i=0;i < P.length;++i){
  triple[] pentagon=sequence(new triple(int k) {
      path3 p=Arc(O,P[i][0],P[i][k+1],nArc);
      return point(p,reltime(p,1/3));
    },5);
  pentagon.cyclic=true;
  draw(sequence(new path3(int k) {
        return Arc(O,pentagon[k],pentagon[k+1],nArc);},5),linewidth(2pt));
  triple M=unit(sum(pentagon)/5);
  for(int i=0;i < 5;++i){
    surface sf=sphericaltriangle(O,pentagon[i],M,pentagon[i+1]);
    draw(sf,black);
  }
}

for(int i=0;i < P.length;++i) {
  for(int j=1;j <= 5;++j) {
    triple K=P[i][0];
    triple A=P[i][j];
    triple B=P[i][(j % 5)+1];
    path3[] p={Arc(O,K,A,nArc),Arc(O,A,B,nArc),Arc(O,B,K,nArc)};
    draw(subpath(p[0],reltime(p[0],1/3),reltime(p[0],2/3)),linewidth(4pt));
    triple[] hexagon={point(p[0],reltime(p[0],1/3)),
                      point(p[0],reltime(p[0],2/3)),
                      point(p[1],reltime(p[1],1/3)),
                      point(p[1],reltime(p[1],2/3)),
                      point(p[2],reltime(p[2],1/3)),
                      point(p[2],reltime(p[2],2/3))};
    hexagon.cyclic=true;
    triple M=unit(sum(hexagon)/6);
    for(int i=0;i < 6;++i) {
      surface sf=sphericaltriangle(O,hexagon[i],M,hexagon[i+1]);
      draw(sf,white);
    }
  }
}
