#dz (predefined symbol)

Type	Readable and writeable	Constant
complex	In perturbinit and perturbloop sections of fractal formulas	No

The #dz predefined symbol represents the difference between the current z value and the z value of the reference orbit when performing perturbation calculations. See perturbation equations for more information.

Example of a Mandelbrot formula that supports perturbation calculations:

PerturbMandelbrot {
init:
  z = 0
loop:
  z = sqr(z) + #pixel
bailout:
  |z| < 4
perturbinit:
  #dz = 0
perturbloop:
  #dz = 2 * #z * #dz + sqr(#dz) + #dpixel
}