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

Hello Bill H. and the VisAD list,

i have (yet) another question about the int[][] Pol_f_Vert
array.

> You mean '9 index entries per vertex'.  The Pol_f_Vert array
> contains lists of polygons adjacent to each vertex, and the
> Vert_f_Pol array contains lists of vertices forming each
> polygon.

> In 'int[] Pol_f_Vert' the information for the i-th vertex is
> in Pol_f_Vert[9*i], Pol_f_Vert[9*i+1], ..., Pol_f_Vert[9*i+8].
> The number of polygons adjacent to vertex i is Pol_f_Vert[9*i+8],
> and the indices of those polygons are in Pol_f_Vert[9*i], ...,
> Pol_f_Vert[9*i + Pol_f_Vert[9*i+8] - 1].

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.

-cheers, bob

PS Thanks to Bill H. for answering my last question(s).

Robert S Laramee        tel:    (603) 868-1361
9 Woodman Ave, #316     office: (603) 862-0350
Durham, NH 03828        URL:   http://www.cs.unh.edu/~rlaramee