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From: "Mark Mather" <mmather@google.com>
Newsgroups: comp.soft-sys.matlab
Subject: simple 3D volume visualization
Date: Tue, 13 May 2008 22:15:03 +0000 (UTC)
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Hello. I have looked over the volume visulization techniques
documentation and I still can't make much sense of it.

It seems the technique here is some form of:

vol3d=patch(isosurface(data,isovalue))

In the scalar data example they use mri data as the volume,
then somehow find the 'skin' on the surface all has an
isovalue of 5. This makes no sense to me, as looking at the
data this is simply not true. What exactly is an isovalue- I
seem to read it is like a contour line but from the example
the skin portion does not seem to be all the points with a
value of 5 (or lower/higher than 5).

Is there a simple clear explanation of what is going on here?   

As a very simple example, take a 20x20x20 zero matrix, and
put random integers in a 5x5x5 cube in the center. How can I
plot the surface of this cube, regardless of the values? How
can I plot just a wire frame of the surface of the cube? 

I have searched but never seem to find any guide on how to
do this other than the official documentation, so if someone
could point me n the right direction to do simple things to
build my technique on that would be greatly appreciated.