A carpeting colored with various shades does not look uniform. Mottled colorations or tweedy effects even on smooth surfaces give an informal ambience. If bright, bold colors are informal, and pale, subtle colors are formal, then those colors in the middle are semi-formal. Most patterns are semiformal. Except for the most powerful and primitive and the most subtle and sophisticated, the majority of patterns can be considered semiformal.
Textures are neither especially rough nor smooth.
To achieve a semiformal effect, textures can be modestly uneven or dimensional. They can be simply smooth without being especially lustrous. Rug and carpet surfaces may be smooth or carved in patterns. Patterns may be large in scale, delicately drawn, crafted by hand, or made of luxurious materials. Most formal patterns are extravagant in some way.