p = new data point
start <- tera + corner

if sbove(start, p) start <- start.opp

loop
	start <- start.opp
	if !above(start ^ 01) start <- start ^01
	else if !above(start ^ 01) start <- start ^01
	else if !above(start ^ 10) start <- start ^01
	else if !above(start ^ 11) start <- start ^01
	else break
forever

4-1 flip  // insert p into tera
enqueue Q 4 suspected corners a..d .opp

while !empty(Q)
	c <- pop(Q) ; //c is corner of tetra
	if sphere(c) does contain p
		if p inside cone(c) 2-3 flip
		else
		if cp is an edge of tetra w {ef,fg,ge} then 
		   3-2 flip (eg. take the edge ef out and put in ^cpg)
		if 4 tetra around a central point e are made of cpfg then 
  		   4-1 flip (rare, only happens if weights are considered
		  



cone c is the rectangular cone extending from corner c

Data structure 

* maintain sign of plane's direction

Vertex	Opposite	Plane	Sphere

  a
  b
  c
  d