31 Oct 2007

## Random walk in the space – fig0010

 (Compiled with Asymptote version 1.84svn-r4619)
```
import three;
settings.render=0;

// The available directions of steps
triple[] dirs={X,-X,Y,-Y,Z,-Z};
dirs.cyclic=true;

// Return the nodes of the path
triple[] randWalk(real Srnd(), int n)
{
triple[] randPath;
triple camera=1e10*currentprojection.camera;
triple pos=O, tpos;
int R;
for (int i=0; i < n; ++i) {
R=round(Srnd());
tpos=pos+dirs[R];
randPath.push(tpos);
pos=tpos;
}
return randPath;
}
triple[] randWalk(int Srnd(), int n)
{
real R(){ return Srnd();}
return randWalk(R,n);
}

void drawWalk(triple[] nodes, pen p=white)
{
triple camera=currentprojection.camera;
if(currentprojection.infinity)
camera *= max(abs(minbound(nodes)),abs(maxbound(nodes)));
real[][] depth;
for(int i=0; i < nodes.length-1; ++i) {
real d=abs(camera-0.5*(nodes[i]+nodes[i+1]));
depth.push(new real[] {d,i});
}
depth=sort(depth);
triple M=nodes[round(depth[0][1])];
triple m=nodes[round(depth[depth.length-1][1]+1)];
// Draw from farthest to nearest
while(depth.length > 0) {
real[] a=depth.pop();
int i=round(a[1]);
draw(nodes[i]--nodes[i+1],abs(nodes[i]-m)/abs(M-m)*p);
}
}

size(18cm);
currentprojection=orthographic((1,1,1));

drawWalk(randWalk(rand,50000),cyan);
shipout(bbox(3mm,Fill));

```

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