II. Similarity - a Gestalt principle of grouping based upon the tendency to group like elements.

C. Pattern, a third kind of similarity, can result from rhythm if the rhythm has regularity and is repeated over a large area. All patterns, therefore, have rhythm but not all rhythms are patterns. If the visual elements which make up a pattern are reduced in size to the point that they are perceived as a fine grain, the image will become texture. Figure 1 is a pattern. Figure 2, although it uses the same shapes as figure 1, is read as texture because the shapes have been drastically reduced in size.
 
Figure 1 Figure 2