**comp.graphics.algorithms**

## Subject: **Re: cell complex indexing**

Thanks for the response. I believe you misunderstood my question. I need

to store data on each cell of the complex, not just the voxels (i.e. data

on vertices, edges, faces, and voxels).

What I ended up doing was to subdivide the grid once (octree style) so I

have a vertex for each cell of the original grid. Index this subdivided

grid normally. Then the dimension of a cell is determined by the number of

odd indices, and you can get the facets/cofacets by adding or subtracting

integer unit vectors depending on which dimensions are odd/even.

Though this is a simple solution, some colleagues suggested augmenting

the (i,j,k) index with an additional facet index which would be

cumbersome.

best

- Taylor

On Wed, 26 Apr 2006, Hans-Bernhard Broeker wrote:

> W. Taylor Holliday

> > Hi Folks,

>

> > Question: what is a good way of indexing a rectilinear voxel grid (3d

> > cell complex) such that you have an index for each cell (vertex, edge,

> > quad face, cube)? and can easily find the facets and co-facets (incidence

> > relationships) of a cell?

>

> The obvious one: cartesian coordinates, e.g. a 3D array of voxels. If

> you can't handle 3D arrayas, you can always map the triplet of indices

> to a single index:

>

> [i][j][k] --> [J*K*i + K*j + k]

>

> --

> Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)

> Even if all the snow were burnt, ashes would remain.

>

___________________________________________________________

W. Taylor Holliday wtholliday.org

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