Snakes (active contour models) are extended to segment regions of interest on the surface of 3D objects. Stereo images taken with calibrated cameras are used as input. For this method the depth map for the whole image does not need to be computed. Instead, 3D external forces are designed to keep the contour on the surface of the object while moving it toward the desired boundaries. Color information is used to improve the ability of snakes in detecting the boundaries, in contrast to the majority of previous methods which are based on intensity information alone. The proposed method produces 3D contours on the surface of the object with coordinates in physical units, e.g. millimeters. These contours can be used to view the structure and dimensions of any distinguishable region on the surface of an object. Examples include oral lesions and skin diseases. The whole process requires minimal human interaction; however, user input can be used to improve segmentation
