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asylum101

metaballs?

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quote:
Original post by Anonymous Poster
What is a metaball?


Please spend a couple of minutes looking for the answer before asking. Why not visit the aforementioned tutorial site www.angelcode.com? The first question answered in the metaball tutorial is "What are metaballs?"

That said, I don''t really like their description. When I think of metaballs, I think of implicit surfaces. Metaballs are a type of implicit surface. Of course, the obvious question for the uninitiated is "what is an implicit surface?" But I don''t have time to answer that here right now.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

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Guest Anonymous Poster
Ah, I don''t care enough to actually look it up.
But, I took the chance that someone might feel like telling me.
I know what the prefix "meta" means, and I know what balls are... but put together it doesn''t make too much sense.
Implicit surface? Ah, nevermind!

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@Anonymous: If you don''t care enough to look up something, why do you bother other people asking? Don''t get me wrong, I think it''s important to ask if you don''t know or don''t understand something, but if it''s worth consuming other peoples'' time you should spend some of your own first investigating on your own (actually searching "metaballs" on Google yields 4650 results, not to mention the link I posted above).

Well, I''m quite sure this wasn''t new to you but it would be nice if you spent a few moments thinking about it, ok?

------------------------------------------------------------
"To a computer, chaos is just another kind of order."

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I didn''t know either and was curious enough to look it up. As far as I can tell ''metaballs'' is a fancy name for 3D graphs of equipotential surfaces. The maths (this IS a maths forum) is well understood as it has various applications in the study of gravitational, eletrical etc. fields. It''s usually covered in undergraduate courses on vector calculus.

The anglecode article and others it refers to seem to be concerned with the graphics side of it, i.e. rendering such surfaces. If this is what the original poster is after it might be worth asking in a graphics forum as judging from the replies here (including my own) the experience of the contributors here is limited.

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In graphics metaballs are useful for the simulation of organic surfaces, and the modeling of complex, nonuniform objects. You assign each ball a radius of influence and then fill in all "voxels" between adjacent spheres where the influence is still felt (ie non-zero). The "field" within this radius falls off as the inverse of the square of the distance IIRC, and the fields are additive (meaning that the individual balls interact to form more complex shapes).

Of course, no one is actually going to fill in unnecessary conceptual voxels, so the marching cubes algorithm is used to determine points along the surface (at reasonable intervals, usually the intersection of the field and the cube edges).

An interesting effect is to include metaballs with negative fields; they look like they took a bite out of the other balls.

Everybody happy?

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