MATLAB Central Newsreader - isosurface visualization

isosurface visualization

misty m. — Fri, 16 May 2008 08:56:03 -0400

hi,
i would like to do some 3d volume visualization. i have CT
images of drilled (in a bone) hole.
from each of images i've found contours of drilled hole-so
i've got (x,y) coefficients of each hole. i decided the
distance between holes = 1. so i've got 3d coeffiecients
for my solid, x,y-coefs of hole and z-distance.
i would like to do the visualization using 'isosurface',
cause i like its effects most, but..

fv = isosurface(X,Y,Z,V,isovalue)

X,Y,Z - i've got
V - i do not have volume
isovalue - what describes it? what value should it have?

i would be really gratefull for any suggestions,
kind regards

Re: isosurface visualization

Michael Garrity — Fri, 16 May 2008 12:52:24 -0400

"misty m." <donotspam@smth.be> wrote in message news:g0ji72$1o5$1@fred.mathworks.com...
> hi,
> i would like to do some 3d volume visualization. i have CT
> images of drilled (in a bone) hole.
> from each of images i've found contours of drilled hole-so
> i've got (x,y) coefficients of each hole. i decided the
> distance between holes = 1. so i've got 3d coeffiecients
> for my solid, x,y-coefs of hole and z-distance.
> i would like to do the visualization using 'isosurface',
> cause i like its effects most, but..
>
> fv = isosurface(X,Y,Z,V,isovalue)
>
> X,Y,Z - i've got
> V - i do not have volume
> isovalue - what describes it? what value should it have?
>
> i would be really gratefull for any suggestions,
> kind regards

No, isosurface works directly from the CT images. You stack
them up to form a 3D array V, and then give that to isosurface.
The isovalue is the level at which you've drawn your contours.

I don't know of a MATLAB function for building a surface
between a set of contours. There are some tricky cases there
when you have a different number of sample points in adjacent
contours or when the topology changes between contours.

-MPG-

Re: isosurface visualization

mark b. — Fri, 16 May 2008 13:11:01 -0400

that explains a lot!
thanks!

Re: isosurface visualization

misty m. — Fri, 16 May 2008 13:34:02 -0400

ok, so is there any function that can gives similar effects
as isosurface but fot x,y,z coeffiecients?
when i try surf:
[A,B,C]=meshgrid(a,b,c)
(where a,b,c are my coeffiecients)
surf(A,B,C) i got:
??? CData must be an M-by-N matrix or M-by-N-by-3 array.

Error in ==> surf at 81
    hh = double(graph3d.surfaceplot(args{:},'parent',cax));

i think that my main problem is that i do not clearly
understand what 'meshgrid' is for. if i have a,b,c coefs
why do i need to do any matrixes? i have a mesh of my
coefs, why can't i simply put them into surf() or mesh()
function?

the other thing is that i've found such a function
surf2patch. it returned me:
   faces: [9216x4 double]
           vertices: [9409x3 double]
    facevertexcdata: [9409x1 double]

can You please explain me, what are these? can i use them
to plot my solid?

kind regards