Escape functions
[2019-06-10] "Escape function" is a variation of the common escape-time technique. Typically, Julia and Mandelbrot sets are plotted by iterating a point with a function, and the point "escapes" if its magnitude goes over a set limit, usually 2. So the "escape target" is the set {z: |z| > 2}. But this can be replaced with an arbitrary function of z. Here I have used simple geometric shapes such as spirals and grids.
The method is related to domain colouring; the colour wheel can be replaced by arbitrary input images, including those of spirals and grids. However, my method combines results from multiple iterations, in a strong analogy with my IFS overlay technique.
[2019-06-14] video clip
