
Hi all,
I have a volume image of blood vessels. I've already calculated the
centerlines of the vessels and stored them in 3*n arrays. I want to
take planar slices perpendicular to a centerline path to get cross
sections of a vessel.
EXTRACT_SLICE does exactly what I want. I specify the center using a
point on the curve, say points[*,i]. I can get the normal vector with
points[*,i+1]  points[*,i]. But I don't understand what the Xvec
argument means.
The description is: "The three values are interpreted as the 0
dimension directional vector. This should be a unit vector." I think
this means that points of the form Origin + k*xvec in the 3D array
(where origin=points[*,i] and k is any real number) will form a
horizontal line in the output plane. If that's correct, though, what
happens if I choose an Xvec that isn't orthogonal to the normal
vector? I'm confused...

