// Pre picture <<<1
import plain_bounds;

include plain_prethree;

// This variable is required by asymptote.sty.
pair viewportsize=0;       // Horizontal and vertical viewport limits.

restricted bool Aspect=true;
restricted bool IgnoreAspect=false;

struct coords3 {
 coord[] x,y,z;
 void erase() {
   x.delete();
   y.delete();
   z.delete();
 }
 // Only a shallow copy of the individual elements of x and y
 // is needed since, once entered, they are never modified.
 coords3 copy() {
   coords3 c=new coords3;
   c.x=copy(x);
   c.y=copy(y);
   c.z=copy(z);
   return c;
 }
 void append(coords3 c) {
   x.append(c.x);
   y.append(c.y);
   z.append(c.z);
 }
 void push(triple user, triple truesize) {
   x.push(coord.build(user.x,truesize.x));
   y.push(coord.build(user.y,truesize.y));
   z.push(coord.build(user.z,truesize.z));
 }
 void push(coord cx, coord cy, coord cz) {
   x.push(cx);
   y.push(cy);
   z.push(cz);
 }
 void push(transform3 t, coords3 c1, coords3 c2, coords3 c3) {
   for(int i=0; i < c1.x.length; ++i) {
     coord cx=c1.x[i], cy=c2.y[i], cz=c3.z[i];
     triple tinf=shiftless(t)*(0,0,0);
     triple z=t*(cx.user,cy.user,cz.user);
     triple w=(cx.truesize,cy.truesize,cz.truesize);
     w=length(w)*unit(shiftless(t)*w);
     coord Cx,Cy,Cz;
     Cx.user=z.x;
     Cy.user=z.y;
     Cz.user=z.z;
     Cx.truesize=w.x;
     Cy.truesize=w.y;
     Cz.truesize=w.z;
     push(Cx,Cy,Cz);
   }
 }
}

// scaleT and Legend <<<
using scalefcn=real(real);

struct scaleT {
 scalefcn T,Tinv;
 bool logarithmic;
 bool automin,automax;
 void operator init(scalefcn T, scalefcn Tinv, bool logarithmic=false,
                    bool automin=false, bool automax=false) {
   this.T=T;
   this.Tinv=Tinv;
   this.logarithmic=logarithmic;
   this.automin=automin;
   this.automax=automax;
 }
 scaleT copy() {
   scaleT dest=scaleT(T,Tinv,logarithmic,automin,automax);
   return dest;
 }
};

scaleT operator init()
{
 scaleT S=scaleT(identity,identity);
 return S;
}

using boundRoutine=void();

struct autoscaleT {
 scaleT scale;
 scaleT postscale;
 real tickMin=-infinity, tickMax=infinity;
 boundRoutine[] bound; // Optional routines to recompute the bounding box.
 bool automin=false, automax=false;
 bool automin() {return automin && scale.automin;}
 bool automax() {return automax && scale.automax;}

 real T(real x) {return postscale.T(scale.T(x));}
 scalefcn T() {return scale.logarithmic ? postscale.T : T;}
 real Tinv(real x) {return scale.Tinv(postscale.Tinv(x));}

 autoscaleT copy() {
   autoscaleT dest=new autoscaleT;
   dest.scale=scale.copy();
   dest.postscale=postscale.copy();
   dest.tickMin=tickMin;
   dest.tickMax=tickMax;
   dest.bound=copy(bound);
   dest.automin=(bool) automin;
   dest.automax=(bool) automax;
   return dest;
 }
}

struct ScaleT {
 bool set;
 autoscaleT x;
 autoscaleT y;
 autoscaleT z;

 ScaleT copy() {
   ScaleT dest=new ScaleT;
   dest.set=set;
   dest.x=x.copy();
   dest.y=y.copy();
   dest.z=z.copy();
   return dest;
 }
};

struct Legend {
 string label;
 pen plabel;
 pen p;
 frame mark;
 bool above;
 void operator init(string label, pen plabel=currentpen, pen p=nullpen,
                    frame mark=newframe, bool above=true) {
   this.label=label;
   this.plabel=plabel;
   this.p=(p == nullpen) ? plabel : p;
   this.mark=mark;
   this.above=above;
 }
}

// >>>

// Frame Alignment was here

triple min3(pen p)
{
 return linewidth(p)*(-0.5,-0.5,-0.5);
}

triple max3(pen p)
{
 return linewidth(p)*(0.5,0.5,0.5);
}

// A function that draws an object to frame pic, given that the transform
// from user coordinates to true-size coordinates is t.
using drawer=void(frame f, transform t);

// A generalization of drawer that includes the final frame's bounds.
// TODO: Add documentation as to what T is.
using drawerBound=void(frame f, transform t, transform T, pair lb, pair rt);

struct node {
 drawerBound d;
 string key;
 void operator init(drawerBound d, string key=xasyKEY()) {
   this.d=d;
   this.key=key;
 }
}

// PairOrTriple <<<1
// This struct is used to represent a userMin/userMax which serves as both a
// pair and a triple depending on the context.
struct pairOrTriple {
 real x,y,z;
 void init() { x=y=z=0; }
};
void copyPairOrTriple(pairOrTriple dest, pairOrTriple src)
{
 dest.x=src.x;
 dest.y=src.y;
 dest.z=src.z;
}
pair operator cast (pairOrTriple a) {
 return (a.x, a.y);
};
triple operator cast (pairOrTriple a) {
 return (a.x, a.y, a.z);
}
void write(pairOrTriple a) {
 write((triple) a);
}

struct picture { // <<<1
 // Nodes <<<2
 // Three-dimensional version of drawer and drawerBound:
 using drawer3=void(frame f, transform3 t, picture pic, projection P);
 using drawerBound3=void(frame f, transform3 t, transform3 T,
                           picture pic, projection P, triple lb, triple rt);

 struct node3 {
   drawerBound3 d;
   string key;
   void operator init(drawerBound3 d, string key=xasyKEY()) {
     this.d=d;
     this.key=key;
   }
 }

 // The functions to do the deferred drawing.
 node[] nodes;
 node3[] nodes3;

 bool uptodate=true;
 bool queueErase=false;
 bool queueErase3=false;

 struct bounds3 {
   coords3 point,min,max;
   bool exact=true; // An accurate picture bounds is provided by the user.
   void erase() {
     point.erase();
     min.erase();
     max.erase();
   }
   bounds3 copy() {
     bounds3 b=new bounds3;
     b.point=point.copy();
     b.min=min.copy();
     b.max=max.copy();
     b.exact=exact;
     return b;
   }
 }

 bounds bounds;
 bounds3 bounds3;

 // Other Fields <<<2
 // Transform to be applied to this picture.
 transform T;
 transform3 T3;

 // The internal representation of the 3D user bounds.
 private pairOrTriple umin, umax;
 private bool usetx, usety, usetz;

 ScaleT scale; // Needed by graph
 Legend[] legend;

 pair[] clipmax; // Used by beginclip/endclip
 pair[] clipmin;

 // The maximum sizes in the x, y, and z directions; zero means no restriction.
 real xsize=0, ysize=0;

 real xsize3=0, ysize3=0, zsize3=0;

 // Fixed unitsizes in the x y, and z directions; zero means use
 // xsize, ysize, and zsize.
 real xunitsize=0, yunitsize=0, zunitsize=0;

 // If true, the x and y directions must be scaled by the same amount.
 bool keepAspect=true;

 // A fixed scaling transform.
 bool fixed;
 transform fixedscaling;

 // Init and erase <<<2
 void init() {
   umin.init();
   umax.init();
   usetx=usety=usetz=false;
   T3=identity(4);
 }
 init();

 // Erase the current picture, retaining bounds.
 void clear() {
   queueErase=nodes.length > 0;
   if(settings.render != 0)
     queueErase3=nodes3.length > 0;
   nodes.delete();
   nodes3.delete();
   legend.delete();
 }

 // Erase the current picture, retaining any size specification.
 void erase() {
   clear();
   bounds.erase();
   bounds3.erase();
   T=identity();
   scale=new ScaleT;
   init();
 }

 // Empty <<<2
 bool empty2() {
   return nodes.length == 0;
 }

 bool empty3() {
   return nodes3.length == 0;
 }

 bool empty() {
   return empty2() && empty3();
 }

 // User min/max <<<2
 pair userMin2() {return bounds.userMin(); }
 pair userMax2() {return bounds.userMax(); }

 bool userSetx2() { return bounds.userBoundsAreSet(); }
 bool userSety2() { return bounds.userBoundsAreSet(); }

 triple userMin3() { return umin; }
 triple userMax3() { return umax; }

 bool userSetx3() { return usetx; }
 bool userSety3() { return usety; }
 bool userSetz3() { return usetz; }

 private using binop=real(real, real);

 // Helper functions for finding the minimum/maximum of two data, one of
 // which may not be defined.
 private static real merge(real x1, bool set1, real x2, bool set2, binop m)
 {
   return set1 ? (set2 ? m(x1,x2) : x1) : x2;
 }
 private pairOrTriple userExtreme(pair u2(), triple u3(), binop m)
 {
   bool setx2=userSetx2();
   bool sety2=userSety2();
   bool setx3=userSetx3();
   bool sety3=userSety3();

   pair p;
   if (setx2 || sety2)
     p=u2();
   triple t=u3();

   pairOrTriple r;
   r.x=merge(p.x, setx2, t.x, setx3, m);
   r.y=merge(p.y, sety2, t.y, sety3, m);
   r.z=t.z;

   return r;
 }

 // The combination of 2D and 3D data.
 pairOrTriple userMin() {
   return userExtreme(userMin2, userMin3, min);
 }
 pairOrTriple userMax() {
   return userExtreme(userMax2, userMax3, max);
 }

 bool userSetx() { return userSetx2() || userSetx3(); }
 bool userSety() { return userSety2() || userSety3(); }
 bool userSetz()=userSetz3;

 // Functions for setting the user bounds.
 void userMinx3(real x) {
   umin.x=x;
   usetx=true;
 }

 void userMiny3(real y) {
   umin.y=y;
   usety=true;
 }

 void userMinz3(real z) {
   umin.z=z;
   usetz=true;
 }

 void userMaxx3(real x) {
   umax.x=x;
   usetx=true;
 }

 void userMaxy3(real y) {
   umax.y=y;
   usety=true;
 }

 void userMaxz3(real z) {
   umax.z=z;
   usetz=true;
 }

 void userMinx2(real x) { bounds.alterUserBound("minx", x); }
 void userMinx(real x) { userMinx2(x); userMinx3(x); }
 void userMiny2(real y) { bounds.alterUserBound("miny", y); }
 void userMiny(real y) { userMiny2(y); userMiny3(y); }
 void userMaxx2(real x) { bounds.alterUserBound("maxx", x); }
 void userMaxx(real x) { userMaxx2(x); userMaxx3(x); }
 void userMaxy2(real y) { bounds.alterUserBound("maxy", y); }
 void userMaxy(real y) { userMaxy2(y); userMaxy3(y); }
 void userMinz(real z)=userMinz3;
 void userMaxz(real z)=userMaxz3;

 void userCorners3(triple c000, triple c001, triple c010, triple c011,
                   triple c100, triple c101, triple c110, triple c111) {
   umin.x=min(c000.x,c001.x,c010.x,c011.x,c100.x,c101.x,c110.x,c111.x);
   umin.y=min(c000.y,c001.y,c010.y,c011.y,c100.y,c101.y,c110.y,c111.y);
   umin.z=min(c000.z,c001.z,c010.z,c011.z,c100.z,c101.z,c110.z,c111.z);
   umax.x=max(c000.x,c001.x,c010.x,c011.x,c100.x,c101.x,c110.x,c111.x);
   umax.y=max(c000.y,c001.y,c010.y,c011.y,c100.y,c101.y,c110.y,c111.y);
   umax.z=max(c000.z,c001.z,c010.z,c011.z,c100.z,c101.z,c110.z,c111.z);
 }

 // Cache the current user-space bounding box x coodinates
 void userBoxX3(real min, real max, binop m=min, binop M=max) {
   if (usetx) {
     umin.x=m(umin.x,min);
     umax.x=M(umax.x,max);
   } else {
     umin.x=min;
     umax.x=max;
     usetx=true;
   }
 }

 // Cache the current user-space bounding box y coodinates
 void userBoxY3(real min, real max, binop m=min, binop M=max) {
   if (usety) {
     umin.y=m(umin.y,min);
     umax.y=M(umax.y,max);
   } else {
     umin.y=min;
     umax.y=max;
     usety=true;
   }
 }

 // Cache the current user-space bounding box z coodinates
 void userBoxZ3(real min, real max, binop m=min, binop M=max) {
   if (usetz) {
     umin.z=m(umin.z,min);
     umax.z=M(umax.z,max);
   } else {
     umin.z=min;
     umax.z=max;
     usetz=true;
   }
 }

 // Cache the current user-space bounding box
 void userBox3(triple min, triple max) {
   userBoxX3(min.x,max.x);
   userBoxY3(min.y,max.y);
   userBoxZ3(min.z,max.z);
 }

 // Add drawer <<<2
 void add(drawerBound d, bool exact=false, bool above=true) {
   uptodate=false;
   if(!exact) bounds.exact=false;
   if(above)
     nodes.push(node(d));
   else
     nodes.insert(0,node(d));
 }

 // Faster implementation of most common case.
 void addExactAbove(drawerBound d) {
   uptodate=false;
   nodes.push(node(d));
 }

 void add(drawer d, bool exact=false, bool above=true) {
   add(new void(frame f, transform t, transform T, pair, pair) {
       d(f,t*T);
     },exact,above);
 }

 void add(drawerBound3 d, bool exact=false, bool above=true) {
   uptodate=false;
   if(!exact) bounds.exact=false;
   if(above)
     nodes3.push(node3(d));
   else
     nodes3.insert(0,node3(d));
 }

 void add(drawer3 d, bool exact=false, bool above=true) {
   add(new void(frame f, transform3 t, transform3 T, picture pic,
                projection P, triple, triple) {
         d(f,t*T,pic,P);
       },exact,above);
 }

 // Clip <<<2
 void clip(pair min, pair max, drawer d, bool exact=false) {
   bounds.clip(min, max);
   this.add(d,exact);
 }

 void clip(pair min, pair max, drawerBound d, bool exact=false) {
   bounds.clip(min, max);
   this.add(d,exact);
 }

 // Add sizing <<<2
 // Add a point to the sizing.
 void addPoint(pair user, pair truesize=0) {
   bounds.addPoint(user,truesize);
   //userBox(user,user);
 }

 // Add a point to the sizing, accounting also for the size of the pen.
 void addPoint(pair user, pair truesize=0, pen p) {
   addPoint(user,truesize+min(p));
   addPoint(user,truesize+max(p));
 }

 void addPoint(triple user, triple truesize=(0,0,0)) {
   bounds3.point.push(user,truesize);
   userBox3(user,user);
 }

 void addPoint(triple user, triple truesize=(0,0,0), pen p) {
   addPoint(user,truesize+min3(p));
   addPoint(user,truesize+max3(p));
 }

 // Add a box to the sizing.
 void addBox(pair userMin, pair userMax, pair trueMin=0, pair trueMax=0) {
   bounds.addBox(userMin, userMax, trueMin, trueMax);
 }

 void addBox(triple userMin, triple userMax, triple trueMin=(0,0,0),
             triple trueMax=(0,0,0)) {
   bounds3.min.push(userMin,trueMin);
   bounds3.max.push(userMax,trueMax);
   userBox3(userMin,userMax);
 }

 // For speed reason, we unravel the addPath routines from bounds.  This
 // avoids an extra function call.
 from bounds unravel addPath;

 // Size commands <<<2
 void size(real x, real y=x, bool keepAspect=this.keepAspect) {
   if(!empty()) uptodate=false;
   xsize=x;
   ysize=y;
   this.keepAspect=keepAspect;
 }

 void size3(real x, real y=x, real z=y, bool keepAspect=this.keepAspect) {
   if(!empty3()) uptodate=false;
   xsize3=x;
   ysize3=y;
   zsize3=z;
   this.keepAspect=keepAspect;
 }

 void unitsize(real x, real y=x, real z=y) {
   uptodate=false;
   xunitsize=x;
   yunitsize=y;
   zunitsize=z;
 }

 // min/max of picture <<<2
 // Calculate the min for the final frame, given the coordinate transform.
 pair min(transform t) {
   return bounds.min(t);
 }

 // Calculate the max for the final frame, given the coordinate transform.
 pair max(transform t) {
   return bounds.max(t);
 }

 // Calculate the min for the final frame, given the coordinate transform.
 triple min(transform3 t) {
   if(bounds3.min.x.length == 0 && bounds3.point.x.length == 0 &&
      bounds3.max.x.length == 0) return (0,0,0);
   triple a=t*(1,1,1)-t*(0,0,0), b=t*(0,0,0);
   scaling xs=scaling.build(a.x,b.x);
   scaling ys=scaling.build(a.y,b.y);
   scaling zs=scaling.build(a.z,b.z);
   return (min(min(min(infinity,xs,bounds3.point.x),xs,bounds3.min.x),
               xs,bounds3.max.x),
           min(min(min(infinity,ys,bounds3.point.y),ys,bounds3.min.y),
               ys,bounds3.max.y),
           min(min(min(infinity,zs,bounds3.point.z),zs,bounds3.min.z),
               zs,bounds3.max.z));
 }

 // Calculate the max for the final frame, given the coordinate transform.
 triple max(transform3 t) {
   if(bounds3.min.x.length == 0 && bounds3.point.x.length == 0 &&
      bounds3.max.x.length == 0) return (0,0,0);
   triple a=t*(1,1,1)-t*(0,0,0), b=t*(0,0,0);
   scaling xs=scaling.build(a.x,b.x);
   scaling ys=scaling.build(a.y,b.y);
   scaling zs=scaling.build(a.z,b.z);
   return (max(max(max(-infinity,xs,bounds3.point.x),xs,bounds3.min.x),
               xs,bounds3.max.x),
           max(max(max(-infinity,ys,bounds3.point.y),ys,bounds3.min.y),
               ys,bounds3.max.y),
           max(max(max(-infinity,zs,bounds3.point.z),zs,bounds3.min.z),
               zs,bounds3.max.z));
 }

 void append(coords3 point, coords3 min, coords3 max, transform3 t,
             bounds3 bounds)
 {
   // Add the coord info to this picture.
   if(t == identity4) {
     point.append(bounds.point);
     min.append(bounds.min);
     max.append(bounds.max);
   } else {
     point.push(t,bounds.point,bounds.point,bounds.point);
     // Add in all 8 corner points, to properly size cuboid pictures.
     point.push(t,bounds.min,bounds.min,bounds.min);
     point.push(t,bounds.min,bounds.min,bounds.max);
     point.push(t,bounds.min,bounds.max,bounds.min);
     point.push(t,bounds.min,bounds.max,bounds.max);
     point.push(t,bounds.max,bounds.min,bounds.min);
     point.push(t,bounds.max,bounds.min,bounds.max);
     point.push(t,bounds.max,bounds.max,bounds.min);
     point.push(t,bounds.max,bounds.max,bounds.max);
   }
 }

 // Scaling and Fit <<<2
 // Returns the transform for turning user-space pairs into true-space pairs.
 transform scaling(real xsize, real ysize, bool keepAspect=true,
                   bool warn=true) {
   bounds b=(T == identity()) ? this.bounds : T * this.bounds;

   return b.scaling(xsize, ysize, xunitsize, yunitsize, keepAspect, warn);
 }

 transform scaling(bool warn=true) {
   return scaling(xsize,ysize,keepAspect,warn);
 }

 // Returns the transform for turning user-space pairs into true-space triples.
 transform3 scaling(real xsize, real ysize, real zsize, bool keepAspect=true,
                    bool warn=true) {
   if(xsize == 0 && xunitsize == 0 && ysize == 0 && yunitsize == 0
      && zsize == 0 && zunitsize == 0)
     return identity(4);

   coords3 Coords;

   append(Coords,Coords,Coords,T3,bounds3);

   real sx;
   if(xunitsize == 0) {
     if(xsize != 0) sx=calculateScaling("x",Coords.x,xsize,warn);
   } else sx=xunitsize;

   real sy;
   if(yunitsize == 0) {
     if(ysize != 0) sy=calculateScaling("y",Coords.y,ysize,warn);
   } else sy=yunitsize;

   real sz;
   if(zunitsize == 0) {
     if(zsize != 0) sz=calculateScaling("z",Coords.z,zsize,warn);
   } else sz=zunitsize;

   if(sx == 0) {
     sx=max(sy,sz);
     if(sx == 0)
       return identity(4);
   }
   if(sy == 0) sy=max(sz,sx);
   if(sz == 0) sz=max(sx,sy);

   if(keepAspect && (xunitsize == 0 || yunitsize == 0 || zunitsize == 0))
     return scale3(min(sx,sy,sz));
   else
     return scale(sx,sy,sz);
 }

 transform3 scaling3(bool warn=true) {
   return scaling(xsize3,ysize3,zsize3,keepAspect,warn);
 }

 frame fit(transform t, transform T0=T, pair m, pair M) {
   frame f;
   for(node n : nodes) {
     xasyKEY(n.key);
     n.d(f,t,T0,m,M);
   }
   return f;
 }

 frame fit3(transform3 t, transform3 T0=T3, picture pic, projection P,
            triple m, triple M) {
   frame f;
   for(node3 n : nodes3) {
     xasyKEY(settings.xasy ? nodes3[0].key : n.key);
     n.d(f,t,T0,pic,P,m,M);
   }
   return f;
 }

 // Returns a rigid version of the picture using t to transform user coords
 // into truesize coords.
 frame fit(transform t) {
   return fit(t,min(t),max(t));
 }

 frame fit3(transform3 t, picture pic, projection P) {
   return fit3(t,pic,P,min(t),max(t));
 }

 // Add drawer wrappers <<<2
 void add(void d(picture, transform), bool exact=false) {
   add(new void(frame f, transform t) {
       picture opic=new picture;
       d(opic,t);
       add(f,opic.fit(identity));
     },exact);
 }

 void add(void d(picture, transform3), bool exact=false, bool above=true) {
   add(new void(frame f, transform3 t, picture pic2, projection P) {
       picture opic=new picture;
       d(opic,t);
       add(f,opic.fit3(identity4,pic2,P));
     },exact,above);
 }

 void add(void d(picture, transform3, transform3, projection, triple, triple),
          bool exact=false, bool above=true) {
   add(new void(frame f, transform3 t, transform3 T, picture pic2,
                projection P, triple lb, triple rt) {
         picture opic=new picture;
         d(opic,t,T,P,lb,rt);
         add(f,opic.fit3(identity4,pic2,P));
       },exact,above);
 }

 // More scaling <<<2
 frame scaled() {
   frame f=fit(fixedscaling);
   pair d=size(f);
   static real epsilon=100*realEpsilon;
   if(d.x > xsize*(1+epsilon))
     warning("xlimit","frame exceeds xlimit: "+(string) d.x+" > "+
             (string) xsize);
   if(d.y > ysize*(1+epsilon))
     warning("ylimit","frame exceeds ylimit: "+(string) d.y+" > "+
             (string) ysize);
   return f;
 }

 // Calculate additional scaling required if only an approximate picture
 // size estimate is available.
 transform scale(frame f, real xsize=this.xsize, real ysize=this.ysize,
                 bool keepaspect=this.keepAspect) {
   if(bounds.exact) return identity();
   pair m=min(f);
   pair M=max(f);
   real width=M.x-m.x;
   real height=M.y-m.y;
   real xgrow=xsize == 0 || width == 0 ? 1 : xsize/width;
   real ygrow=ysize == 0 || height == 0 ? 1 : ysize/height;
   if(keepAspect) {
     real[] grow;
     if(xsize > 0) grow.push(xgrow);
     if(ysize > 0) grow.push(ygrow);
     return scale(grow.length == 0 ? 1 : min(grow));
   } else return scale(xgrow,ygrow);

 }

 // Calculate additional scaling required if only an approximate picture
 // size estimate is available.
 transform3 scale3(frame f, real xsize3=this.xsize3,
                   real ysize3=this.ysize3, real zsize3=this.zsize3,
                   bool keepaspect=this.keepAspect) {
   if(bounds3.exact) return identity(4);
   triple m=min3(f);
   triple M=max3(f);
   real width=M.x-m.x;
   real height=M.y-m.y;
   real depth=M.z-m.z;
   real xgrow=xsize3 == 0 || width == 0 ? 1 : xsize3/width;
   real ygrow=ysize3 == 0 || height == 0 ? 1 : ysize3/height;
   real zgrow=zsize3 == 0 || depth == 0 ? 1 : zsize3/depth;
   if(keepAspect) {
     real[] grow;
     if(xsize3 > 0) grow.push(xgrow);
     if(ysize3 > 0) grow.push(ygrow);
     if(zsize3 > 0) grow.push(zgrow);
     return scale3(grow.length == 0 ? 1 : min(grow));
   } else return scale(xgrow,ygrow,zgrow);
 }

 // calculateTransform with scaling <<<2
 // Return the transform that would be used to fit the picture to a frame
 transform calculateTransform(real xsize, real ysize, bool keepAspect=true,
                              bool warn=true) {
   transform t=scaling(xsize,ysize,keepAspect,warn);
   return scale(fit(t),xsize,ysize,keepAspect)*t;
 }

 transform calculateTransform(bool warn=true) {
   if(fixed) return fixedscaling;
   return calculateTransform(xsize,ysize,keepAspect,warn);
 }

 transform3 calculateTransform3(real xsize=xsize3, real ysize=ysize3,
                                real zsize=zsize3,
                                bool keepAspect=true, bool warn=true,
                                projection P=currentprojection) {
   transform3 t=scaling(xsize,ysize,zsize,keepAspect,warn);
   return scale3(fit3(t,null,P),keepAspect)*t;
 }

 // min/max with xsize and ysize <<<2
 // NOTE: These are probably very slow as implemented.
 pair min(real xsize=this.xsize, real ysize=this.ysize,
          bool keepAspect=this.keepAspect, bool warn=true) {
   return min(calculateTransform(xsize,ysize,keepAspect,warn));
 }

 pair max(real xsize=this.xsize, real ysize=this.ysize,
          bool keepAspect=this.keepAspect, bool warn=true) {
   return max(calculateTransform(xsize,ysize,keepAspect,warn));
 }

 triple min3(real xsize=this.xsize3, real ysize=this.ysize3,
             real zsize=this.zsize3, bool keepAspect=this.keepAspect,
             bool warn=true, projection P) {
   return min(calculateTransform3(xsize,ysize,zsize,keepAspect,warn,P));
 }

 triple max3(real xsize=this.xsize3, real ysize=this.ysize3,
             real zsize=this.zsize3, bool keepAspect=this.keepAspect,
             bool warn=true, projection P) {
   return max(calculateTransform3(xsize,ysize,zsize,keepAspect,warn,P));
 }

 // More Fitting <<<2
 // Returns the 2D picture fit to the requested size.
 frame fit2(real xsize=this.xsize, real ysize=this.ysize,
            bool keepAspect=this.keepAspect) {
   if(fixed) return scaled();
   if(empty2())
     return newframe;

   transform t=scaling(xsize,ysize,keepAspect);
   frame f=fit(t);
   transform s=scale(f,xsize,ysize,keepAspect);
   if(s == identity()) return f;
   return fit(s*t);
 }

 static frame fitter(string,picture,string,real,real,bool,bool,string,string,
                     light,projection);
 frame fit(string prefix="", string format="",
           real xsize=this.xsize, real ysize=this.ysize,
           bool keepAspect=this.keepAspect, bool view=false,
           string options="", string script="", light light=currentlight,
           projection P=currentprojection) {
   return fitter == null ? fit2(xsize,ysize,keepAspect) :
     fitter(prefix,this,format,xsize,ysize,keepAspect,view,options,script,
            light,P);
 }

 // Fit a 3D picture.
 frame fit3(projection P=currentprojection) {
   if(settings.render == 0) return fit(P);
   if(fixed) return scaled();
   if(empty3()) return newframe;
   transform3 t=scaling(xsize3,ysize3,zsize3,keepAspect);
   frame f=fit3(t,null,P);
   transform3 s=scale3(f,xsize3,ysize3,zsize3,keepAspect);
   if(s == identity4) return f;
   return fit3(s*t,null,P);
 }

 // In case only an approximate picture size estimate is available, return the
 // fitted frame slightly scaled (including labels and true size distances)
 // so that it precisely meets the given size specification.
 frame scale(real xsize=this.xsize, real ysize=this.ysize,
             bool keepAspect=this.keepAspect) {
   frame f=fit(xsize,ysize,keepAspect);
   transform s=scale(f,xsize,ysize,keepAspect);
   if(s == identity()) return f;
   return s*f;
 }

 // Copying <<<2

 // Copies enough information to yield the same userMin/userMax.
 void userCopy2(picture pic) {
   userMinx2(pic.userMin2().x);
   userMiny2(pic.userMin2().y);
   userMaxx2(pic.userMax2().x);
   userMaxy2(pic.userMax2().y);
 }

 void userCopy3(picture pic) {
   copyPairOrTriple(umin, pic.umin);
   copyPairOrTriple(umax, pic.umax);
   usetx=pic.usetx;
   usety=pic.usety;
   usetz=pic.usetz;
 }

 void userCopy(picture pic) {
   userCopy2(pic);
   userCopy3(pic);
 }

 // Copies the drawing information, but not the sizing information into a new
 // picture. Fitting this picture will not scale as the original picture would.
 picture drawcopy() {
   picture dest=new picture;
   dest.nodes=copy(nodes);
   dest.nodes3=copy(nodes3);
   dest.T=T;
   dest.T3=T3;

   // TODO: User bounds are sizing info, which probably shouldn't be part of
   // a draw copy.  Should we move this down to copy()?
   dest.userCopy3(this);

   dest.scale=scale.copy();
   dest.legend=copy(legend);

   return dest;
 }

 // A deep copy of this picture.  Modifying the copied picture will not affect
 // the original.
 picture copy() {
   picture dest=drawcopy();

   dest.uptodate=uptodate;
   dest.bounds=bounds.copy();
   dest.bounds3=bounds3.copy();

   dest.xsize=xsize; dest.ysize=ysize;
   dest.xsize3=xsize; dest.ysize3=ysize3; dest.zsize3=zsize3;
   dest.keepAspect=keepAspect;
   dest.xunitsize=xunitsize; dest.yunitsize=yunitsize;
   dest.zunitsize=zunitsize;
   dest.fixed=fixed; dest.fixedscaling=fixedscaling;

   return dest;
 }

 // Helper function for defining transformed pictures.  Do not call it
 // directly.
 picture transformed(transform t) {
   picture dest=drawcopy();

   // Replace nodes with a single drawer that realizes the transform.
   node[] oldnodes=dest.nodes;
   void drawAll(frame f, transform tt, transform T, pair lb, pair rt) {
     transform Tt=T*t;
     for (node n : oldnodes) {
       xasyKEY(n.key);
       n.d(f,tt,Tt,lb,rt);
     }
   }
   dest.nodes=new node[] {node(drawAll)};

   dest.uptodate=uptodate;
   dest.bounds=bounds.transformed(t);
   dest.bounds3=bounds3.copy();

   dest.bounds.exact=false;

   dest.xsize=xsize; dest.ysize=ysize;
   dest.xsize3=xsize; dest.ysize3=ysize3; dest.zsize3=zsize3;
   dest.keepAspect=keepAspect;
   dest.xunitsize=xunitsize; dest.yunitsize=yunitsize;
   dest.zunitsize=zunitsize;
   dest.fixed=fixed; dest.fixedscaling=fixedscaling;

   return dest;
 }

 // Add Picture <<<2
 // Add a picture to this picture, such that the user coordinates will be
 // scaled identically when fitted
 void add(picture src, bool group=true, filltype filltype=NoFill,
          bool above=true) {
   // Copy the picture.  Only the drawing function closures are needed, so we
   // only copy them.  This needs to be a deep copy, as src could later have
   // objects added to it that should not be included in this picture.

   if(src == this) abort("cannot add picture to itself");

   uptodate=false;

   picture srcCopy=src.drawcopy();
   // Draw by drawing the copied picture.
   if(srcCopy.nodes.length > 0) {
     nodes.push(node(new void(frame f, transform t, transform T,
                              pair m, pair M) {
         add(f,srcCopy.fit(t,T*srcCopy.T,m,M),group,filltype,above);
         }));
   }

   if(srcCopy.nodes3.length > 0) {
     nodes3.push(node3(new void(frame f, transform3 t, transform3 T3,
                                picture pic, projection P, triple m, triple M)
                       {
                   add(f,srcCopy.fit3(t,T3*srcCopy.T3,pic,P,m,M),group,above);
                       }));
   }

   legend.append(src.legend);

   if(src.usetx) userBoxX3(src.umin.x,src.umax.x);
   if(src.usety) userBoxY3(src.umin.y,src.umax.y);
   if(src.usetz) userBoxZ3(src.umin.z,src.umax.z);

   bounds.append(srcCopy.T, src.bounds);
   //append(bounds.point,bounds.min,bounds.max,srcCopy.T,src.bounds);
   append(bounds3.point,bounds3.min,bounds3.max,srcCopy.T3,src.bounds3);

   //if(!src.bounds.exact) bounds.exact=false;
   if(!src.bounds3.exact) bounds3.exact=false;
 }
}

// Post Struct <<<1
picture operator * (transform t, picture orig)
{
 return orig.transformed(t);
}

picture operator * (transform3 t, picture orig)
{
 picture pic=orig.copy();
 pic.T3=t*pic.T3;
 triple umin=pic.userMin3(), umax=pic.userMax3();
 pic.userCorners3(t*umin,
                  t*(umin.x,umin.y,umax.z),
                  t*(umin.x,umax.y,umin.z),
                  t*(umin.x,umax.y,umax.z),
                  t*(umax.x,umin.y,umin.z),
                  t*(umax.x,umin.y,umax.z),
                  t*(umax.x,umax.y,umin.z),
                  t*umax);
 pic.bounds3.exact=false;
 return pic;
}

picture currentpicture;

void size(picture pic=currentpicture, real x, real y=x,
         bool keepAspect=pic.keepAspect)
{
 pic.size(x,y,keepAspect);
}

void size(picture pic=currentpicture, transform t)
{
 if(pic.empty3()) {
   pair z=size(pic.fit(t));
   pic.size(z.x,z.y);
 }
}

void size3(picture pic=currentpicture, real x, real y=x, real z=y,
          bool keepAspect=pic.keepAspect)
{
 pic.size3(x,y,z,keepAspect);
}

void unitsize(picture pic=currentpicture, real x, real y=x, real z=y)
{
 pic.unitsize(x,y,z);
}

void size(picture pic=currentpicture, real xsize, real ysize,
         pair min, pair max)
{
 pair size=max-min;
 pic.unitsize(size.x != 0 ? xsize/size.x : 0,
              size.y != 0 ? ysize/size.y : 0);
}

void size(picture dest, picture src)
{
 dest.size(src.xsize,src.ysize,src.keepAspect);
 dest.size3(src.xsize3,src.ysize3,src.zsize3,src.keepAspect);
 dest.unitsize(src.xunitsize,src.yunitsize,src.zunitsize);
}

pair min(picture pic, bool user=false)
{
 transform t=pic.calculateTransform();
 pair z=pic.min(t);
 return user ? inverse(t)*z : z;
}

pair max(picture pic, bool user=false)
{
 transform t=pic.calculateTransform();
 pair z=pic.max(t);
 return user ? inverse(t)*z : z;
}

pair size(picture pic, bool user=false)
{
 transform t=pic.calculateTransform();
 pair M=pic.max(t);
 pair m=pic.min(t);
 if(!user) return M-m;
 t=inverse(t);
 return t*M-t*m;
}

// Return a projection adjusted to view center of pic from specified direction.
projection centered(projection P, picture pic=currentpicture) {
 projection P=P.copy();
 if(P.autoadjust && P.center) {
   triple min=pic.userMin3();
   triple max=pic.userMax3();
   if(min != max) {
     triple target=0.5*(max+min);
     if(pic.keepAspect)
       P.camera=target+P.vector();
     else
       P.camera=target+realmult(unit(P.vector()),max-min);
     P.target=target;
     P.normal=P.vector();
     P.calculate();
   }
 }
 return P;
}

// Frame Alignment <<<
pair rectify(pair dir)
{
 real scale=max(abs(dir.x),abs(dir.y));
 if(scale != 0) dir *= 0.5/scale;
 dir += (0.5,0.5);
 return dir;
}

pair point(frame f, pair dir)
{
 pair m=min(f);
 pair M=max(f);
 return m+realmult(rectify(dir),M-m);
}

path[] align(path[] g, transform t=identity(), pair position,
            pair align, pen p=currentpen)
{
 if(g.length == 0) return g;
 pair m=min(g);
 pair M=max(g);
 pair dir=rectify(inverse(t)*-align);
 if(basealign(p) == 1)
   dir -= (0,m.y/(M.y-m.y));
 pair a=m+realmult(dir,M-m);
 return shift(position+align*labelmargin(p))*t*shift(-a)*g;
}

// Returns a transform for aligning frame f in the direction align
transform shift(frame f, pair align)
{
 return shift(align-point(f,-align));
}

// Returns a copy of frame f aligned in the direction align
frame align(frame f, pair align)
{
 return shift(f,align)*f;
}
// >>>

pair point(picture pic=currentpicture, pair dir, bool user=true)
{
 pair umin=pic.userMin2();
 pair umax=pic.userMax2();

 pair z=umin+realmult(rectify(dir),umax-umin);
 return user ? z : pic.calculateTransform()*z;
}

pair truepoint(picture pic=currentpicture, pair dir, bool user=true)
{
 transform t=pic.calculateTransform();
 pair m=pic.min(t);
 pair M=pic.max(t);
 pair z=m+realmult(rectify(dir),M-m);
 return user ? inverse(t)*z : z;
}

// Transform coordinate in [0,1]x[0,1] to current user coordinates.
pair relative(picture pic=currentpicture, pair z)
{
 return pic.userMin2()+realmult(z,pic.userMax2()-pic.userMin2());
}

void add(picture pic=currentpicture, drawer d, bool exact=false)
{
 pic.add(d,exact);
}

using drawer3=void(frame f, transform3 t, picture pic, projection P);
void add(picture pic=currentpicture, drawer3 d, bool exact=false)
{
 pic.add(d,exact);
}

void add(picture pic=currentpicture, void d(picture,transform),
        bool exact=false)
{
 pic.add(d,exact);
}

void add(picture pic=currentpicture, void d(picture,transform3),
        bool exact=false)
{
 pic.add(d,exact);
}

void begingroup(picture pic=currentpicture)
{
 pic.add(new void(frame f, transform) {
     begingroup(f);
   },true);
}

void endgroup(picture pic=currentpicture)
{
 pic.add(new void(frame f, transform) {
     endgroup(f);
   },true);
}

void Draw(picture pic=currentpicture, path g, pen p=currentpen)
{
 pic.add(new void(frame f, transform t) {
     draw(f,t*g,p);
   },true);
 pic.addPath(g,p);
}

// Default arguments have been removed to increase speed.
void _draw(picture pic, path g, pen p, margin margin)
{
 if (size(nib(p)) == 0 && margin==NoMargin) {
   // Inline the drawerBound wrapper for speed.
   pic.addExactAbove(new void(frame f, transform t, transform T, pair, pair) {
       _draw(f,t*T*g,p);
     });
 } else {
   pic.add(new void(frame f, transform t) {
       draw(f,margin(t*g,p).g,p);
     },true);
 }
 pic.addPath(g,p);
}

void Draw(picture pic=currentpicture, explicit path[] g, pen p=currentpen)
{
 // Could optimize this by adding one drawer.
 for(int i=0; i < g.length; ++i) Draw(pic,g[i],p);
}

void fill(picture pic=currentpicture, path[] g, pen p=currentpen,
         bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.add(new void(frame f, transform t) {
     fill(f,t*g,p,false);
   },true);
 pic.addPath(g);
}

void drawstrokepath(picture pic=currentpicture, path g, pen strokepen,
                   pen p=currentpen)
{
 pic.add(new void(frame f, transform t) {
     draw(f,strokepath(t*g,strokepen),p);
   },true);
 pic.addPath(g,p);
}

void latticeshade(picture pic=currentpicture, path[] g, bool stroke=false,
                 pen fillrule=currentpen, pen[][] p, bool copy=true)
{
 if(copy) {
   g=copy(g);
   p=copy(p);
 }
 pic.add(new void(frame f, transform t) {
     latticeshade(f,t*g,stroke,fillrule,p,t,false);
   },true);
 pic.addPath(g);
}

void axialshade(picture pic=currentpicture, path[] g, bool stroke=false,
               pen pena, pair a, bool extenda=true,
               pen penb, pair b, bool extendb=true, bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.add(new void(frame f, transform t) {
     axialshade(f,t*g,stroke,pena,t*a,extenda,penb,t*b,extendb,false);
   },true);
 pic.addPath(g);
}

void radialshade(picture pic=currentpicture, path[] g, bool stroke=false,
                pen pena, pair a, real ra, bool extenda=true,
                pen penb, pair b, real rb, bool extendb=true, bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.add(new void(frame f, transform t) {
     pair A=t*a, B=t*b;
     real RA=abs(t*(a+ra)-A);
     real RB=abs(t*(b+rb)-B);
     radialshade(f,t*g,stroke,pena,A,RA,extenda,penb,B,RB,extendb,false);
   },true);
 pic.addPath(g);
}

void gouraudshade(picture pic=currentpicture, path[] g, bool stroke=false,
                 pen fillrule=currentpen, pen[] p, pair[] z, int[] edges,
                 bool copy=true)
{
 if(copy) {
   g=copy(g);
   p=copy(p);
   z=copy(z);
   edges=copy(edges);
 }
 pic.add(new void(frame f, transform t) {
     gouraudshade(f,t*g,stroke,fillrule,p,t*z,edges,false);
   },true);
 pic.addPath(g);
}

void gouraudshade(picture pic=currentpicture, path[] g, bool stroke=false,
                 pen fillrule=currentpen, pen[] p, int[] edges, bool copy=true)
{
 if(copy) {
   g=copy(g);
   p=copy(p);
   edges=copy(edges);
 }
 pic.add(new void(frame f, transform t) {
     gouraudshade(f,t*g,stroke,fillrule,p,edges,false);
   },true);
 pic.addPath(g);
}

void tensorshade(picture pic=currentpicture, path[] g, bool stroke=false,
                pen fillrule=currentpen, pen[][] p, path[] b=new path[],
                pair[][] z=new pair[][], bool copy=true)
{
 bool compact=b.length == 0 || b[0] == nullpath;
 if(copy) {
   g=copy(g);
   p=copy(p);
   if(!compact) b=copy(b);
   z=copy(z);
 }
 pic.add(new void(frame f, transform t) {
     pair[][] Z=new pair[z.length][];
     for(int i=0; i < z.length; ++i)
       Z[i]=t*z[i];
     path[] G=t*g;
     if(compact)
       tensorshade(f,G,stroke,fillrule,p,Z,false);
     else
       tensorshade(f,G,stroke,fillrule,p,t*b,Z,false);
   },true);
 pic.addPath(g);
}

void tensorshade(frame f, path[] g, bool stroke=false,
                pen fillrule=currentpen, pen[] p,
                path b=g.length > 0 ? g[0] : nullpath, pair[] z=new pair[])
{
 tensorshade(f,g,stroke,fillrule,new pen[][] {p},b,
             z.length > 0 ? new pair[][] {z} : new pair[][]);
}

void tensorshade(picture pic=currentpicture, path[] g, bool stroke=false,
                pen fillrule=currentpen, pen[] p,
                path b=nullpath, pair[] z=new pair[])
{
 tensorshade(pic,g,stroke,fillrule,new pen[][] {p},b,
             z.length > 0 ? new pair[][] {z} : new pair[][]);
}

// Smoothly shade the regions between consecutive paths of a sequence using a
// given array of pens:
void draw(picture pic=currentpicture, path[] g, pen fillrule=currentpen,
         pen[] p)
{
 path[] G;
 pen[][] P;
 string differentlengths="arrays have different lengths";
 if(g.length != p.length) abort(differentlengths);
 for(int i=0; i < g.length-1; ++i) {
   path g0=g[i];
   path g1=g[i+1];
   if(length(g0) != length(g1)) abort(differentlengths);
   for(int j=0; j < length(g0); ++j) {
     G.push(subpath(g0,j,j+1)--reverse(subpath(g1,j,j+1))--cycle);
     P.push(new pen[] {p[i],p[i],p[i+1],p[i+1]});
   }
 }
 tensorshade(pic,G,fillrule,P);
}

void functionshade(picture pic=currentpicture, path[] g, bool stroke=false,
                  pen fillrule=currentpen, string shader, bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.add(new void(frame f, transform t) {
     functionshade(f,t*g,stroke,fillrule,shader);
   },true);
 pic.addPath(g);
}

void filldraw(picture pic=currentpicture, path[] g, pen fillpen=currentpen,
             pen drawpen=currentpen)
{
 begingroup(pic);
 fill(pic,g,fillpen);
 Draw(pic,g,drawpen);
 endgroup(pic);
}

void clip(picture pic=currentpicture, path[] g, bool stroke=false,
         pen fillrule=currentpen, bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.clip(min(g), max(g),
          new void(frame f, transform t) {
            clip(f,t*g,stroke,fillrule,false);
          },
          true);
}

void beginclip(picture pic=currentpicture, path[] g, bool stroke=false,
              pen fillrule=currentpen, bool copy=true)
{
 if(copy)
   g=copy(g);

 pic.clipmin.push(min(g));
 pic.clipmax.push(max(g));

 pic.add(new void(frame f, transform t) {
     beginclip(f,t*g,stroke,fillrule,false);
   },true);
}

void endclip(picture pic=currentpicture)
{
 pair min,max;
 if (pic.clipmin.length > 0 && pic.clipmax.length > 0)
   {
     min=pic.clipmin.pop();
     max=pic.clipmax.pop();
   }
 else
   {
     // We should probably abort here, since the PostScript output will be
     // garbage.
     warning("endclip", "endclip without beginclip");
     min=pic.userMin2();
     max=pic.userMax2();
   }

 pic.clip(min, max,
          new void(frame f, transform) {
            endclip(f);
          },
          true);
}

void unfill(picture pic=currentpicture, path[] g, bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.add(new void(frame f, transform t) {
     unfill(f,t*g,false);
   },true);
}

void filloutside(picture pic=currentpicture, path[] g, pen p=currentpen,
                bool copy=true)
{
 if(copy)
   g=copy(g);
 pic.add(new void(frame f, transform t) {
     filloutside(f,t*g,p,false);
   },true);
 pic.addPath(g);
}

// Use a fixed scaling to map user coordinates in box(min,max) to the
// desired picture size.
transform fixedscaling(picture pic=currentpicture, pair min, pair max,
                      pen p=nullpen, bool warn=false)
{
 Draw(pic,min,p+invisible);
 Draw(pic,max,p+invisible);
 pic.fixed=true;
 return pic.fixedscaling=pic.calculateTransform(pic.xsize,pic.ysize,
                                                pic.keepAspect);
}

// Add frame src to frame dest about position with optional grouping.
void add(frame dest, frame src, pair position, bool group=false,
        filltype filltype=NoFill, bool above=true)
{
 add(dest,shift(position)*src,group,filltype,above);
}

// Add frame src to picture dest about position with optional grouping.
void add(picture dest=currentpicture, frame src, pair position=0,
        bool group=true, filltype filltype=NoFill, bool above=true)
{
 if(is3D(src)) {
   dest.add(new void(frame f, transform3, picture, projection) {
       add(f,src); // always add about 3D origin (ignore position)
     },true);
   dest.addBox((0,0,0),(0,0,0),min3(src),max3(src));
 } else {
   dest.add(new void(frame f, transform t) {
       add(f,shift(t*position)*src,group,filltype,above);
     },true);
   dest.addBox(position,position,min(src),max(src));
 }
}

// Like add(picture,frame,pair) but extend picture to accommodate frame.
void attach(picture dest=currentpicture, frame src, pair position=0,
           bool group=true, filltype filltype=NoFill, bool above=true)
{
 transform t=dest.calculateTransform();
 add(dest,src,position,group,filltype,above);
 pair s=size(dest.fit(t));
 size(dest,dest.xsize != 0 ? s.x : 0,dest.ysize != 0 ? s.y : 0);
}

// Like add(picture,frame,pair) but align frame in direction align.
void add(picture dest=currentpicture, frame src, pair position, pair align,
        bool group=true, filltype filltype=NoFill, bool above=true)
{
 add(dest,align(src,align),position,group,filltype,above);
}

// Like add(frame,frame,pair) but align frame in direction align.
void add(frame dest, frame src, pair position, pair align,
        bool group=true, filltype filltype=NoFill, bool above=true)
{
 add(dest,align(src,align),position,group,filltype,above);
}

// Like add(picture,frame,pair,pair) but extend picture to accommodate frame;
void attach(picture dest=currentpicture, frame src, pair position,
           pair align, bool group=true, filltype filltype=NoFill,
           bool above=true)
{
 attach(dest,align(src,align),position,group,filltype,above);
}

// Add a picture to another such that user coordinates in both will be scaled
// identically in the shipout.
void add(picture dest, picture src, bool group=true, filltype filltype=NoFill,
        bool above=true)
{
 dest.add(src,group,filltype,above);
}

void add(picture src, bool group=true, filltype filltype=NoFill,
        bool above=true)
{
 currentpicture.add(src,group,filltype,above);
}

// Fit the picture src and add it about the point position to picture dest.
void add(picture dest, picture src, pair position, bool group=true,
        filltype filltype=NoFill, bool above=true)
{
 add(dest,src.fit(),position,group,filltype,true);
}

void add(picture src, pair position, bool group=true, filltype filltype=NoFill,
        bool above=true)
{
 add(currentpicture,src,position,group,filltype,above);
}

// Fill a region about the user-coordinate 'origin'.
void fill(pair origin, picture pic=currentpicture, path[] g, pen p=currentpen)
{
 picture opic;
 fill(opic,g,p);
 add(pic,opic.fit(identity),origin);
}

void postscript(picture pic=currentpicture, string s)
{
 pic.add(new void(frame f, transform) {
     postscript(f,s);
   },true);
}

void postscript(picture pic=currentpicture, string s, pair min, pair max)
{
 pic.add(new void(frame f, transform t) {
     postscript(f,s,t*min,t*max);
   },true);
}

void tex(picture pic=currentpicture, string s)
{
 // Force TeX string s to be evaluated immediately (in case it is a macro).
 frame g;
 tex(g,s);
 size(g);
 pic.add(new void(frame f, transform) {
     tex(f,s);
   },true);
}

void tex(picture pic=currentpicture, string s, pair min, pair max)
{
 frame g;
 tex(g,s);
 size(g);
 pic.add(new void(frame f, transform t) {
     tex(f,s,t*min,t*max);
   },true);
}

void layer(picture pic=currentpicture)
{
 pic.add(new void(frame f, transform) {
     layer(f);
   },true);
}

void erase(picture pic=currentpicture)
{
 pic.uptodate=false;
 pic.erase();
}

void begin(picture pic=currentpicture, string name, string id="",
          bool visible=true)
{
 if(!latex() || !pdf()) return;
 settings.twice=true;
 if(id == "") id=string(++ocgindex);
 tex(pic,"\begin{ocg}{"+name+"}{"+id+"}{"+(visible ? "1" : "0")+"}");
 layer(pic);
}

void end(picture pic=currentpicture)
{
 if(!latex() || !pdf()) return;
 tex(pic,"\end{ocg}%");
 layer(pic);
}

// For users of the LaTeX babel package.
void deactivatequote(picture pic=currentpicture)
{
 tex(pic,"\catcode`\"=12");
}

void activatequote(picture pic=currentpicture)
{
 tex(pic,"\catcode`\"=13");
}