Robert P. Munafo, 2012 Apr 20.
The values of Zn that are calculated during an iteration process. The iterates form a sequence of points Zn (also called the point's orbit or the critical orbit of the point's Julia set), with one member for each positive integer n. The sequence is defined by the recurrence relation:
Z0 = 0
Zn+1 = Zn2 + C
where C is the point for which the iteration is being performed.
If the values of Zn diverge to infinity by getting progressively larger and larger, the point C is not in the Mandelbrot set.
If the values follow a chaotic, non-repeating pattern and never diverge to infinity the point is in the Mandelbrot Set and also on the boundary. Not all points on the boundary have chaotic iteration, however. The Misiurewicz points are the best examples. See also accuracy.
Typically in practice one needs to limit how many times the calculation Zn+1 = Zn2 + C is performed, using a maximum dwell value of some kind. See the page on algorithms for more information about how to write a Mandelbrot program.
Much more informative pictures can be produced with the extra information provided by the distance estimator algorithm.
Julia sets can be plotted via the inverse iteration method.
See also inverse Mandelbrot iteration.
From the Mandelbrot Set Glossary and Encyclopedia, by Robert Munafo, (c) 1987-2012. Mu-ency index