The dashed cyan contours are the boundaries of the capture ranges obtained by segmenting the external force field, and are used as the initial snakes.
Li, Jundong Liu, and Martin D. Fox, “Segmentation of Edge Preserving
Gradient Vector Flow: An Approach Toward Automatic Initialization and Splitting of
Snakes”, IEEE International
Computer Vision and Pattern Recognition
(CVPR), San Diego, 2005.