[efcdzagl] Random pipes on a 3D lattice

Animate a random walk within a cubical lattice, keeping marked traversed edges.  Inspired by the "pipes" screensaver.

Avoid going over the same edge twice.  More restrictively, avoid visiting the same node twice.  There's some lookahead required to avoid running into dead ends.  Somewhat reminiscent of Paterson's Worm.

Incidentally, consider ways of avoiding dead ends on 2D lattices.  This is similar to heuristics for solving mazes.

Instead of the cubical lattice, consider the lattice of the tetrahedral-octahedral honeycomb (alternated cubic honeycomb).  12 edges exit each node, twice that of the cubical lattice, though this is not too useful if a node can be visited at most once.

Prefer paths that stay within the viewport (frustrum) of the fixed camera.  Prefer paths that stay close to the camera.

What angle should the camera be pointed to avoid near nodes obscuring farther nodes?  If it is an orthographic projection, then some irrational slope would do (which one is best?).  What about perspective projection?