Three-dimensional missing size mark finding method based on difference track

The invention discloses a three-dimensional missing size mark finding method based on a difference track. The three-dimensional missing size mark finding method is characterized by comprising the steps of obtaining a generation rule of the difference track on the basis of a track intersection method and a rigid body recognition method, establishing a missing size mark finding procedure of a geometrical element on the basis of the generation rule, and finding size marks, namely, the to-be-found missing size marks of a part, required by combination of all rigid bodies according to the finding procedure. According to the reverse reasoning track interaction method, the mapping relations between the missing size marks and the difference track are established, and the difference track generation rule is established. Then, according to the rule and the mapping relation, the least missing size mark extraction procedure of the geometrical element is established by taking the smallest number of size marking as the principle. The extraction algorithm of the missing size marks between the rigid bodies is established by analyzing rigid conditions of equivalent positioning tuples of the rigid bodies, and the size marks added due to combination of the rigid bodies serve as the missing size marks recommended to the part.