Shaw <sha### [at] activech> wrote:
> That got me thinking.
> Water in my experience seems to be made of more concave surfaces than
> positive curved ones.  The blob surfaces that I have built, and they
are
> many, tend toward convex. Flowing blobs look like mercury. I have put
a lot
> of work in to build flat and concave ones, but there is usually an
easier
> way.
>
> Looking at the flowing water image it struck me that there was an
easier
> logic in what was happening above the liquid than in the liquid
itself.  For
> example to model the liquid clinging to the wall with blobs would be
nasty,
> stacked up in a pyramid configuration, sliding off the wall, surface
tension
> pulling the border back.  But if the negative space was modeled then
only
> one element would give the same curve against the wall, a sphere, or a
> collection of sphere's blobbed together.
>
> So giving it a shot, the image is a first attempt to recreate the
Arete
> animation.  The base element is a box, differenced with a blob,
consisting
> randomly placed, randomly sized and randomly strengthed spherical
elements,
> the "pour" is a cylindrical blob element that is negative to the other
> positive blob elements.   The whole thing is given a media content and
> rendered.  No animation steps, rendering time is five hours on a
pentium II
> 400.
>
> Now, since the direction is to model the space above the blob, I have
in my
> head a mental image of a box filled with ping pong balls, into which
is
> poured a stream of large ball bearings.  The "ping pong balls" are the
blob
> elements they form essentially a solid of the top of the "liquid".
For the
> sake of this first concept the "ball bearings", are not rendered, they
serve
> to displace the larger and convex "ping pong balls", or air molecules,
only
> the lower surface of the blob "cloud" is rendered, as it boolean's the
box.
>
> I had seen this approach somewhere and it took racking my brain to
remember,
> there is a small shareware program that does beautiful animations of
> particles and I highly recommend downloading it and playing with it,
it will
> open your eyes.   The program is called "Really" and it is written by
> Giovanni Tummarelli in Italy, the program is a little bit rough in
places,
> but it lets one design arrangements of "atoms" and their character and
let
> them go at each other the objects collide and shiver and break apart
in real
> time, nothing short of amazing.    Load the "World" called Diver2 and
watch,
> think of the application of this in a Povray animation with blobs. It
is all
> of 450K big, and here is the URL;
> http://www.ascu.unian.it/~tummarel/really.shtml  (considering the
trouble I
> had to go through to find it again, I would humbly nominate it for
inclusion
> in Ken's wondrous page of links, if only to make it easier to find the
next
> time.)
>
> So, in conclusion, to render the water, it may be simple to render the
> invisible air.

An interesting exercise in lateral thinking, that's for sure!  Talking
of concave blob surfaces, perhaps negative components could be used to
get more of the shape you're after?  Beyond that, maybe it's time to
look at isosurfaces...?  (And no, Tony, I've yet to get 'round to giving
the SuperPatch a proper workout... but if all the currently custom
features become official in POV-Ray 3.5 I won't have any excuses not
to!).

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