Active contours without edges - help

[physical101]

Hi there I have been investigating active contours without edges recently and have become stuck with the evolution of phi along the level set. I understand most of the basics but was wondering if anyone who is familar with active contours without edges could tell me how to evolve phi. Currently I am using the pixel coordinates of phi and then adding a timestep multiplied by force information derived from the image to move get new coordinate info for the contour. Is this correct? Are the elements of phi supposed to multiplied?
Any help will be much appreciated
Physical 101

 

[Future Bruno]

The evolution of phi along the level set is based on the concept of deformable contours. Essentially, a contour (or curve) is deformed by the application of forces to its points. The forces can be derived from the image itself or from other external sources. The application of these forces is calculated using the equation: \phi(x,t+1)=\phi(x,t)+\Delta t \cdot F(x,t)Where \phi(x,t) represents the coordinates of the contour at time t and F(x,t) is the force applied to the contour at that time. The timestep \Delta t is a small constant used to calculate the amount of displacement of the contour due to the applied force.In order to evolve phi along the level set, you must iteratively apply the above equation for each point on the contour. It is important to note that the elements of phi are not multiplied, but instead added together in order to compute the new position of the contour.