An algorithm for generating new mandelbrot and julia sets

Computer Engineering and Intelligent Systems www.iiste.org
ISSN 2222-1719 (Paper) ISSN 2222-2863 (Online)
Vol 3, No.1, 2012

An Algorithm for Generating New Mandelbrot and Julia Sets
R. P. Pant1 R. K. Bisht1*
1. Department of Mathematics, D. S. B. Campus, Kumaun University, Nainital-263002, India
* E-mail of the corresponding author: ravindra.bisht@yahoo.com

Abstract

The present paper is motivated from the paper of John R. Tippetts (Tippetts 1992) in which he gave an
algorithm to generate an interesting Mandelbrot set. We not only generate Julia sets using Tippetts
algorithm (Tippetts 1992), but also generate some new Julia and Mandelbrot sets by slightly modifying the
Tippetts algorithm. This approach yields a new class of algorithms to produce new and alluring fractals
with virtually infinite complexity.

Keywords: Mandelbrot set, Julia set, recursion formula, algorithm

1. Introduction

The study of complex iterated polynomials has been a very active field of research activity during the last
two decades. The study of Julia sets and Mandelbrot sets derived from polynomials is an area of abiding
interest in the field of fractal geometry (Peitgen et al 2006).

The well-known algorithm for generating Mandelbrot set from the recursion formula;
Z → Z2 + C (where Z = x + iy and C = a + ib), requires the following steps (Peitgen et al 2006):
[1] xnew = x2 – y2 + a
[2] ynew = 2xy + b
[3] x = xnew
[4] y = ynew
[5] return to step (1).

For Mandelbrot set, a point (a, b) belongs to the set if, after repeated iteration, x and y remain finite (x and y
being initially zero). In 1992, John R. Tippetts gave a simple algorithm for generating an interesting
Mandelbrot set by slightly modifying the above algorithm. He replaced ynew and xnew by y and x
respectively (Tippetts 1992) and got the following algorithm:

[1] x = x2 – y2 + a
[2] y = 2xy + b
[3] return to step (1).

Then, simply by putting value of x from step (1) to step (2), Tippetts got an explicit equation for the new
y-value:
ynew = 2x2 y – 2y3 + 2ay + b,

which produces a new class of fractals having virtually infinite complexity.

In this paper we generate a new Julia set using the Tippetts algorithm (Tippetts 1992). We also generate
some new Mandelbrot and Julia sets by slightly modifying Tippetts algorithm. Like the Tippetts algorithm,

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the modified algorithm is also very interesting.

2. Main Results
The main steps required to display the Julia sets for the recursion Z → Z2 + C (where Z = x + iy and C = a
+ ib), consists the following statements (Peitgen et al 2006):

(1) xnew = x2 – y2 + a
(2) ynew = 2xy + b
(3) x = xnew
(4) y = ynew
(5) return to step (1).

For fixed C, a point x, y belongs to the set if, after repeated iteration, steps (1) and (2) remain finite.
Following Tippetts (Tippetts 1992) we can replace ynew by simply y. Further, if we also replace xnew by
x so that the steps (3) and (4) can be discarded. Now only three statements remain:

(1) x = x2 – y2 + a
(2) y = 2xy + b

Now, simply by putting value of x from step (1) to step (2), we get an explicit equation for the new y-value
which is same as (Tippetts 1992):
ynew = 2x2 y – 2y3 + 2ay + b.

The algorithm formed by the above statements is equivalent to the following:

(1) xnew = x2 – y2 + a
(2) ynew = 2x2 y – 2y3 + 2ay + b
(3) x = xnew
(4) y = ynew

The corresponding Julia set for the above algorithm, contains fractal boundary. Julia set of the above
algorithm for C= -1.0+0i, is the boundary between the inner capture zone and the outer regions of fast
escape is shown in Figure1. The Julia set and its zoomed-in view for C=-0.73+0.40i are shown in Figures 2
and 3.
In the next section, we generate some new fractals containing both Julia set and Mandelbrot set, by slightly
modifying the algorithm:

(1) x = x2 – y2 + a
(2) y = 2xy + b

In the above algorithm by putting value of y from step (2) to step (1), we get an explicit equation for the

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new x-value:

xnew = x2 – 4 x2y2 + 4bxy - b2 + a.

The newly formed algorithm is equivalent to the following statements:

(1) xnew = x2 – 4 x2y2 + 4bxy - b2 + a
(2) ynew = 2xy + b
(3) x = xnew
(4) y = ynew

For Mandelbrot set, a point (a, b) belongs to the set if, after repeated iteration, x and y remain finite (x and y
being initially zero) (Tippetts 1992). The corresponding Mandelbrot set for the quartic function xnew
along with ynew is shown in Figure 4 and represents the boundary between the inner capture zone (black)
and the outer regions of fast escape (yellow). Other zoomed-in views for Mandelbrot set [M-Set] are shown
in Figures 6 and 7.

Again, Julia set for fixed C= -0.1+0i, a point (x, y) belongs to the set if, after repeated iteration, steps 1 and
2 remain finite. The corresponding Julia set for the quartic function xnew along with ynew is shown in
Figure 7 and represents the boundary between the inner capture zone and the outer regions of fast escape.
Some other Julia sets for different C-values are shown in Figures 8 and 9.

3. Conclusion:
Many interesting fractals can be generated from the modified algorithm for the recursion formula Z → Z2
+ C. This approach opens up scope for obtaining new algorithms with more complex iterated functions
having fascinating fractal boundaries.

4. Generation of Julia Sets using Tippetts algorithm:

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Figure1 Julia set for C = (-1.0, 0)

Figure 2 Julia set for C = (-0.73+0.40i)

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Figure 3 Zoomed in-view for C = (-0.73+0.40i)

5. Generation of Mandelbrot Sets using modified algorithm:

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Figure 4 Mandelbrot set for x-new

Figure 5 Zoomed in view for M. Set.

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Figure 6 Zoomed in view for M. Set.

6. Generation of Julia Sets using modified algorithm:

Figure 7 Julia set for, (C=-0.1+0 i)

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Figure 8 Julia set for, C=(0.66- 0.12 i)

Figure 9 Julia set for, (C=-0.73 +0.40 i)

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References

[1] Tippetts, John R. (1992), “A Simple Algorithm Giving an Interesting Mandelbrot Set”, The
visual computer 8, Springer-Verlag , 200-201.
[2] Mandelbrot B. B. (1980), “Fractal Aspects of the Iteration of z → z (1 - z) for Complex
and z”, Ann of NY Acad Sci 357, 249-259.
[3] Peitgen H.O., Jurgens H. & Saupe D. (2006), “Chaos and Fractals”, New Frontier of Science,
(2nd edition), MR2031217.

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An algorithm for generating new mandelbrot and julia sets

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