1. A vision system for a vehicle, said vision system comprising: an image sensor disposed at a subject vehicle and having an exterior field of view exterior of the subject vehicle; a control, wherein said control comprises a processor that processes image data captured by said image sensor to detect objects present exterior of the subject vehicle and in the field of view of said image sensor; wherein said control processes captured image data to detect points of interest of an object present in the field of view of said image sensor, and wherein detected points of interest of the detected object comprise detected corner features of the detected object that is present in the field of view of said image sensor, and wherein the detected object has a height above ground, and wherein the detected corner features of the detected object are disposed at respective heights of the detected object above ground; wherein said control processes captured image data to determine movement vectors of the detected points of interest of the detected object, and wherein, responsive to said processing of captured image data, said control determines whether determined movement vectors of detected points of interest of the detected object present in the field of view of said image sensor are indicative of an object of interest present in the field of view of said image sensor; wherein a parabolic region of interest in which objects exterior of the subject vehicle are likely objects of interest is defined by a parabolic boundary having an apex located centrally within the field of view of said image sensor and above a middle region of the field of view of said image sensor; and wherein determined movement vectors that are less than a threshold pixel length are not considered indicative of an object of interest, and wherein the detected object is not considered an object of interest when the detected corner features of the detected object are above and outside the parabolic boundary of the parabolic region of interest.