Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!titan!foo
From: foo@titan.rice.edu (Mark Hall)
Newsgroups: comp.graphics
Subject: Re: Blobbly Polygons
Summary: Blobby molecules are implicit surfaces
Keywords: meta-ball, blobby molecules
Message-ID: <2607@kalliope.rice.edu>
Date: 16 Feb 89 15:32:29 GMT
References: <439@celia.UUCP>
Sender: usenet@rice.edu
Reply-To: foo@titan.rice.edu (Mark Hall)
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Organization: Rice University, Houston
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In article <439@celia.UUCP> celia!charlie@tis.llnl.gov (Charlie Gibson) writes:
>Can anyone recommend some references for "Meta-Sphere" or "Blobby Molecule"
>algorithms that create a tesselated 3-d geometry? (as opposed to scanline
>algorithms for direct rendering of these primitives)
>
>-- 
>Charlie Gibson                                | What IS the secret powder
>Rhythm & Hues, Inc.                           | that makes "Orange Julius"

   The surfaces of these blobby molecules are implicitly defined.
  That is, they are defined by a single equation

       f(x, y, z) = 0

   I assume that you have seen Blinn's '82 paper on rendering these directly.
  It was printed in ACM transactions on Graphics, and pointed to in that
  year's SIGGRAPH proceedings. 

   In the last couple of years several people have looked into using 
  polygonal representations of implicit surfaces. Implicit surfaces
  are becoming a little more popular because they are nice for defining
  "blending surfaces". My advisor wrote his thesis on the form the implicit
  blending surface needs to be in. Data that is in the form of spatially
  arranged density data can also be viewed by picking a level set to be
  the surface of interest. Lots of data is in this form: CT scan, NMR, 
  some seismic data, etc. 

    Back to your initial question: what are some references on 
  polygonalizing these things?

   Blinn, J., (1982)
   A Generalization of Algebraic Surface Drawing,
   ACM Transactions on Graphics, Vol. 1, Number 3, pp. 235-256.

   Wyvil, G.,McPheeters, C., and Wyvil, B., (1986)
   ``Data structure for  soft objects",
    The Visual Computer,2:227-234.

   Lorenson, W., and Cline, H. (1987)
   ``Marching Cubes: A High Resolution 3D Surface Construction Algorithm",
    Computer Graphics, Volume 21, No. 4, pp. 163-169.

   Duurst, M. J. (1988),
   "Additional Reference to Marching Cubes", 
   Computer Graphics, 
   Volume 22, No. 2, pp. 72,73.

   Bloomenthal, J., (1988) 
   Polygonalization of Implicit Surfaces,
   Computer Aided Geometric Design 5 (1988), pp. 341-355.
   (also Xerox Report CSL-87-2. and in SIGGRAPH course notes (87 & 88?))

   Hall, M., and Warren, J. (1988)
   "Adaptive Tessellation of Implicitly Defined Surfaces",
   (Submitted for publication  and Rice Technical report)
   *copies on e-mail request*


   As mentioned before, Blinn rendered these things directly. 
   The brothers Wyvil have done a lot of work incorporating these objects
   into their Graphicsland environment at U. Calgary. I see some
   of their students posting in this group, if you have questions 
   for them. Lorenson and Cline 
   showed a table lookup algorithm that is quite nice. It does have 
   (at least) one bug, a consequence of which is pointed out by Duurst,
   but I have used it in a number of applications with pleasing results.
   Bloomenthal presents an algorithmic approach with the added feature 
   of being able to adaptively approximate the surface. That is, where
   the surface is flat[ter], use fewer but larger polygons to approximate it.
   His algorithm is tricky to implement correctly by his own admission. 
   Joe Warren and I found a different method for adaptively polygonalizing
   the surface that we think is easier to implement. 

   Hope this helps. 

   - mark