Sigh. My corporate email is still not getting through, so this is
from my alter ego. Originally sent yesterday.
I would like to thank Dr. Donna L. Gresh for her help in using
the colormap for defining a transfer function. I am doing
"segmentation" of images in which I want to select certain
gray levels. In particular, arteries given slightly higher density
You need to take a look at the Print module. I think you are ready to
understand how useful it is. Especially, attach Print to any output,
then set it to "rd" (double-click on Print module to open dialog
box). The output (when Execute Once is performed) appears in the
Message Window. Use the Contextual Help (Help Menu) to click on the
Print module for more info.
You will (hopefully) understand why some of your operations are
indeed superfluous and in fact, your overall description of your net
suggests that you may be doing several unnecessary steps. DX is
actually easier than you think! (:-) But you have to understand how
the various modules affect the contents of a field, and Print is the
way I've always used to best advantage.
I'm guessing that you could do this:
Import then send to Colormap and Color with Colormap output also
feeding Color (I believe you figured this part out already). This
gives you a field with both "data" and "colors", wherein the colors
are derived from the data. But now you want to treat the "colors" as
a type of data. Thus, Mark("colors") copies the 3-vector of "colors"
into the component called "data" (it also backs up the old "data" but
we'll save that for another time). So now, Compute, Isosurface etc.
will all attempt to operate on that 3-vector "data". Only problem is
that Isosurface cannot operate on a vector, so you use Compute to do
something like "mag(a)" to get vector magnitude, or "a.x + a.y + a.z"
as you have (although I'm not sure that's a very useful calculation).
You could also do "norm(a)" to normalize or any of a zillion other
functions or operations, but "mag(a)" is sufficient to yield a scalar
"data" output that Isosurface likes.
To learn with Print, attach it first to Import's output, run the net,
examine the Message Window. Then, disconnect Print and move it down
to the output of Color and execute again and so on. Especially, note
the names of the components that occur at each step: you'll always
see "positions", usually see "connections", and assuming there is
some, you'll see "data". After Color or Autocolor, you'll see
"colors" appear, IN ADDITION TO ALL THE PREVIOUS! (important point
that I think you are missing). And so on.
Cheers on your progress!
--
Chris Pelkie
Scientific Visualization Producer
618 Rhodes Hall Cornell Theory Center, Cornell University
Ithaca, NY 14853
