Pickover stalks are certain kinds of details to be found empirically in the Mandelbrot set, in the study of fractal geometry. [1] They are so named after the researcher Clifford Pickover, whose "epsilon cross" method was instrumental in their discovery. An "epsilon cross" is a cross-shaped orbit trap.
According to Vepstas (1997) "Pickover hit on the novel concept of looking to see how closely the orbits of interior points come to the x and y axes. In these pictures, the closer that the point approaches, the higher up the color scale, with red denoting the closest approach. The logarithm of the distance is taken to accentuate the details". [2]
Biomorphs are biological-looking Pickover Stalks. [3] At the end of the 1980s, Pickover developed biological feedback organisms similar to Julia sets and the fractal Mandelbrot set. [4] According to Pickover (1999) in summary, he "described an algorithm that can be used for the creation of diverse and complicated forms resembling invertebrate organisms. The shapes are complicated and difficult to predict before actually experimenting with the mappings." He hoped "these techniques will encourage [others] to explore further and discover new forms, by accident, that are on the edge of science and art". [5]
Pickover developed an algorithm (which uses neither random perturbations nor natural laws) to create very complicated forms resembling invertebrate organisms. The iteration, or recursion, of mathematical transformations is used to generate biological morphologies. He called them "biomorphs." At the same time he coined "biomorph" for these patterns, the famous evolutionary biologist Richard Dawkins used the word to refer to his own set of biological shapes that were arrived at by a very different procedure. More rigorously, Pickover's "biomorphs" encompass the class of organismic morphologies created by small changes to traditional convergence tests in the field of "Julia set" theory. [5]
Pickover's biomorphs show a self-similarity at different scales, a common feature of dynamical systems with feedback. Real systems, such as shorelines and mountain ranges, also show self-similarity over some scales. A 2-dimensional parametric 0L system can “look” like Pickover's biomorphs. [6]
The below example, written in pseudocode, renders a Mandelbrot set colored using a Pickover Stalk with a transformation vector and a color dividend.
The transformation vector is used to offset the (x, y) position when sampling the point's distance to the horizontal and vertical axis.
The color dividend is a float used to determine how thick the stalk is when it is rendered.
For each pixel (x, y) on the target, do: { zx = scaled x coordinate of pixel (scaled to lie in the Mandelbrot X scale (-2.5, 1)) zy = scaled y coordinate of pixel (scaled to lie in the Mandelbrot Y scale (-1, 1)) float2 c = (zx, zy) //Offset in the Mandelbrot formulae float x = zx; //Coordinates to be iterated float y = zy; float trapDistance = 1000000; //Keeps track of distance, set to a high value at first. int iteration = 0; while (x*x + y*y < 4 && iteration < maxIterations) { float2 z = float2(x, y); z = cmul(z, z); // z^2, cmul is a multiplication function for complex numbers z += c; x = z.x; y = z.y; float distanceToX = abs(z.x + transformationVector.x); //Checks the distance to the vertical axis float distanceToY = abs(z.y + transformationVector.y); //Checks the distance to the horizontal axis smallestDistance = min(distanceToX, distanceToY); // Use only smaller axis distance trapDistance = min(trapDistance, smallestDistance); iteration++; } return trapDistance * color / dividend; //Dividend is an external float, the higher it is the thicker the stalk is }
In mathematics, a fractal is a geometric shape containing detailed structure at arbitrarily small scales, usually having a fractal dimension strictly exceeding the topological dimension. Many fractals appear similar at various scales, as illustrated in successive magnifications of the Mandelbrot set. This exhibition of similar patterns at increasingly smaller scales is called self-similarity, also known as expanding symmetry or unfolding symmetry; if this replication is exactly the same at every scale, as in the Menger sponge, the shape is called affine self-similar. Fractal geometry lies within the mathematical branch of measure theory.
The Mandelbrot set is a two-dimensional set with a relatively simple definition that exhibits great complexity, especially as it is magnified. It is popular for its aesthetic appeal and fractal structures. The set is defined in the complex plane as the complex numbers for which the function does not diverge to infinity when iterated starting at , i.e., for which the sequence , , etc., remains bounded in absolute value.
In mathematics, a self-similar object is exactly or approximately similar to a part of itself. Many objects in the real world, such as coastlines, are statistically self-similar: parts of them show the same statistical properties at many scales. Self-similarity is a typical property of fractals. Scale invariance is an exact form of self-similarity where at any magnification there is a smaller piece of the object that is similar to the whole. For instance, a side of the Koch snowflake is both symmetrical and scale-invariant; it can be continually magnified 3x without changing shape. The non-trivial similarity evident in fractals is distinguished by their fine structure, or detail on arbitrarily small scales. As a counterexample, whereas any portion of a straight line may resemble the whole, further detail is not revealed.
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Clifford Alan Pickover is an American author, editor, and columnist in the fields of science, mathematics, science fiction, innovation, and creativity. For many years, he was employed at the IBM Thomas J. Watson Research Center in Yorktown, New York, where he was editor-in-chief of the IBM Journal of Research and Development. He has been granted more than 700 U.S. patents, is an elected Fellow for the Committee for Skeptical Inquiry, and is author of more than 50 books, translated into more than a dozen languages.
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