POV-Ray's crackle pattern - crackle metric/offset

The crackle pattern is one of POV-Ray's most useful and flexible patterns. Because the additional parameters introduced in megapov I made this collection of sample pictures.

The pictures are rendered with POV-Ray 3.5 beta which does not produce the same results as in megapov 0.x with metrics different from 2.

The parameters illustrated here are "metric" and "offset" used the following way:

pigment {   crackle   metric FLOAT   offset FLOAT   color_map {     ...   } }

color_map used: