Since your cells are discretized to 2 values (0 ignored), how can you have any meaningful Isosurface other than =7 or =3? And therefore, how can a single surface adequately show the extent of a complete cell, other than to show its boundary? In other words, Isosurface's triangles inherently cut through your discrete cells, and could therefore cut at any angle and anywhere along the length or breadth of the cell. Therefore, none of these cuts fully represents the data within the cell; all are equally insufficient representations. Therefore, the technique 'lies' or misrepresents. And you don't have a CIA director to fall back on.
So, just turn on or off the set of cells =7 (Include) to reveal those =3 (or vice versa) and observe that 'sparse' matrix (ShowBoundary). It will look like a Lego construction (sort of). I think that's the closest you can come to illustrating how the iso-valued cells connect spatially, which is essentially what Isosurface is doing.
Under continuum conditions, Isosurface of 3.8 or 5.25 would mean something, and would be found by intersecting the triangles of the Isosurface with the cell edges at newly created positions along the cell edges, at the points where those 'iso' values are computed from the cell's 'corner' data. Then, by definition, the entire Isosurface has the same (iso) value (like 3.8) and colors the same. For a variation, see one of the samples (I can't think of the name offhand, but it has the Thundercloud data in it), that Maps the (continuous) volumetric data onto an Isosurface. However, in your case, this will not give the desired result (I'm pretty sure), since it will undoubtedly create triangles (in the Isosurface) that have =7 at 1 or 2 vertices and =3 at the other(s), and you'll get a gruesome looking color contour across the faces. (One way to minimize the ugliness is to make a color map whose Saturation curve dips to white at 5, then set Hue to blue=7 and red=3. Thus, you should get only shades of blue and red fading to white.)
Something else to try is MaptoPlane which can deal with discretized (connection-dependent) data/colors in the original sample volume (I did it recently so I know this is true). You can slice this plane through your volume any way you want and all slices will be representative, since they'll all look like randomized checkerboards.
On Wednesday, Jul 23, 2003, at 16:54 America/New_York, Brendan M Johnson wrote:
So all looks good with Isosurface except for the coloring. Isosurface_______________________________
is using a gradient and my data is discrete cells that I want a solid
color. So in a regular grid, all cells with value of 7 are blue all cells
with value of 3 are red and all cells with value 0 are ignored.
Tried coloring before and after isosurface. Tried changing the
gradient. Tried a bunch of "re-wiring" and still get (at best) the shading
from isosurface.
So can I get isosurface to accept a different color map or
reconstruct the 3D object from isosurface form different components and
throw my coloring into it?
Brendan
Chris Pelkie
Scientific Visualization Producer
622 Rhodes Hall, Cornell Theory Center
Ithaca, NY 14853
