Abstract: This paper presents an algorithm for generating turtle back pattern, a traditional national pattern. The algorithm is based on the analysis of the mathematical rules of turtle back pattern. It mainly analyzes the motif of turtle back pattern, and then obtains the primitive elements of the motif from the symmetry of the primitive. After the rotation and symmetry of the primitive elements, the motif is obtained, and the whole turtle back pattern is obtained by tiling the motif. Moreover, through the formulation of the primitive elements, we get the generalization generation formula of turtle back pattern. By introducing certain parameters, we can generate a large number of similar but different patterns. The experimental results also verify the feasibility of this method, which is of great significance for the digital preservation of national traditional patterns.

Key words: CAD, turtle back pattern, pattern generate, computer graphics