> this will only be useful if you have 
> a high number of particles that fill a bounded area

	Right -- in fact I was talking about treatment of many particles.

> and do not change 
> their distribution in space very fast.  If this is not the case you will 
> spent most of your time doing the list building.

	Not necessarily.  With smarter algorithm you could subdivide
space and update the pairwise list only in places where particles move
faster.  The list build still represent O(N) simple operations anyway.

> And as you already said your space division grid will only work if you 
> have only point masses with all the same radius.

	No, just pick the larger object first to decide what grid spacing
to use.  Of course this still make sense when all objects are about the
same size (ie _not_ one or two orders of magnitude difference in their
largest dimension).

> The original topic of 
> this discussion was mass-triangle collisions with varying radii.

	Yes, sorry, for some reason I assumed that the main problem was
coming from a high number of particles to deal with, while I realize
now that the topic deals with the inner function of the collision
detection.  Still, it might be nice to be able to speed up the many-
particles problem  :-)

	- NC

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