Re: Gridded3DSet.isosurf() and int[][] Pol_f_Vert

• To: Robert S Laramee <rlaramee@xxxxxxxxxxxxxxx>
• Subject: Re: Gridded3DSet.isosurf() and int[][] Pol_f_Vert
• From: "From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>" <billh@xxxxxxxxxxxxx>
• Date: Sat, 18 Mar 2000 15:39:12 -0600 (CST)

Hi Bob,

> In the implementation of the isosurf() method, the construction of the
> Pol_f_Vert[] array is based on the notion that 1 vertex may be shared (or
> adjacent to) by a maximum of 8 polygons.  I'm wondering where this result
> is derived from.  In other words, why is 8 the maximum number of polygons
> shared by a vertex.  The reason I am wondering is because in our own
> implementation of Marching Cubes (taken from the Visualization Toolkit),
> as far as I can tell, I'm getting a result that says a vertex can be
> shared by up to 9 polygons.  I seem to be getting this result fairly
> consistently and I don't know, at this writing, whether or not this is a
> valid result.

In our isosurf method, a vertex lies on a cube edge so is adjacent
to at most four cubes, and there can be at most two polygons
adjacent to a vertex from one cube.

I wouldn't worry too much about it.  I'd either use our
isosurf as is, or replace it with your own.

By the way, we recently added a new method makeContour()
to ShadowType to make it easier to define new extensions
of DataRenderer with radically different approaches to
contours.

Cheers,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • Re: Gridded3DSet.isosurf() and int[][] Pol_f_Vert
    • From: Robert S Laramee