Orbit trap

In mathematics, an orbit trap is a method of colouring fractal images based upon how close an iterative function, used to create the fractal, approaches a geometric shape, called a "trap". Typical traps are points, lines, circles, flower shapes and even raster images. Orbit traps are typically used to colour two dimensional fractals representing the complex plane.
Examples
Point based
A point based orbit trap colours a point based upon how close a function's orbit comes to a single point, typically the origin.
Line based
A line based orbit trap colours a point based upon how close a function's orbit comes to one or more lines, typically vertical or horizontal (x=a or y=a lines). Pickover stalks are an example of a line based orbit trap which use two lines.
Algorithm
Orbit traps are typically used with the class of two-dimensional fractals based on an iterative function. A program that creates such a fractal colours...