I am trying to create an animation of a leukocyte recruitment cascade, 
which in plain English is the process by which immune cells leave the 
blood in order to enter tissues.

Any way's, I've got the whole thing pretty much done but I've run into 
one problem which I cannot seem to lick.  At one step of the process the 
  cell I'm modeling has to squeeze through a narrow gap.  The best 
description I can think of would be squeezing a water balloon through a 
tube which is smaller then the balloon.  So you'd start with a sphere on 
one side of the "tube", mid-way you'd have two equal sized spheres on 
either side of the tube with a connecting "neck", and finally you'd end 
up with a sphere on the opposite side of the membrane.

The only way I've been able to model this in povray is to use blobs; 
this was animated by slowly expanding the size/strength of an invisible 
sphere to "pull" the other sphere through the gap.  A couple of 
negative-strength spheres maintained the proper "neck" size.  While this 
achieves the effect I desire I end up loosing the internal structure  of 
the cell.  To try and keep the image of this structure, I tried mapping 
a JPEG of the cell onto the sphere representing the cell, but it ended 
up being so distorted as to be pointless.

I also tried using the blob command to "pull" my cell through.  My cell 
is defined in a separate .inc file as a union of various basic shapes 
(plus some media, etc, to make it pretty).  I tried to use the cell 
union as the visible part of my blob, but this didn't work as blob 
appears to be limited to simple objects.

Does anyone know of a way to achieve this effect?

Thanx in advance

Bryan Heit

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