[Insight-users] Question about Levelset

[m26402022 at john.petra.ac.id]

Hello,

   My name is Yohan. I need some assisstance in Levelset.

  I've made an application using levelset method. based on the paper I've found
on website there are three things I want to ask:

 1. Distance (z = d(x,y,t=0))

    All I know z is the distance of a point(x,y) to our initial curvature in
    Normal direction.
    So I make it this way, I have 10x10 image plain and I made a circle as an
    initial curve. The result is:

    3  2  2  2  2  2  3  3  4  5
    2  1  1  1  1  1  2  3  3  4   is this is what the distance means(z)??
    1  1  0  0  0  1  1  2  3  4
    1  0 -1 -1 -1  0  1  1  2  3   0 values are the initial curvature (circle)
    0 -1 -2 -2 -2 -1  0  1  2  3   + values are the point outside init. circle
    0 -1 -2 -3 -2 -1  0  1  2  3   - values are the point inside init. circle
    0 -1 -2 -2 -2 -1  0  1  2  3
    1  0 -1 -1 -1  0  1  1  2  3
    1  1  0  0  0  1  1  2  3  4
    2  1  1  1  1  1  2  3  3  4

 2. Speed function F(K)=F + F (k)=(1-eK)
                         0   1

    K is the curvature and all I know is :

              2                       2
        dxx dy - 2 dx dy dxy + dyy dx           Note : d  is the distance
    K = -----------------------------------    xx means second derivative to x
                     2    2  3/2
                  (dx + dy  )

    I want to ask about derivative, what is the correct way to calculate first
derivative
    and second derivative, can I use sobel??

                                                      2    2  3/2
    Also about the divider from equation k wich is (dx + dy  )    . if i use
sobel there are
    some condition where the result is a zero. so the equation cannot be done
because the divider
    is zero. what should I do with it??


Regards,


Yohan