// G-Force DeltaField
// Name: HAL_Julia_Seahorse
// Created by: Howard A. Landman, 16 May 2001
// e-mail: howard@polyamory.org -or- howard.landman@vitesse.com
// homepage: http://www.polyamory.org/~howard/

// This DeltaField refracts the waves through the lens of a Julia set,
// the fractal generated by the recursion relation z = z^2 + c
// for z = (x + i*y)
// and c = 0.74543 - 0.11301i
// This particular Julia set is fairly famous
// and is known as the "seahorse".
//
// It is not possible to code a true Julia set recursion as a DeltaField
// (DFs can be 1-to-1 or 1-to-many mappings, but Julia sets are many-to-1)
// so this is the "reverse" Julia recursion.  The difference is that a
// forward one would have everything flowing away from the set boundary -
// points outside the set would head off to infinity while points inside
// the set would spiral down into attractive basins (with points on or
// near the boundary bouncing around chaotically).  In a reverse one,
// points outside the set are sucked onto it, while points inside spiral
// up out of the basins to get plastered against the boundary as well.
// Usually the interior is visually more interesting, so we want it to
// fill as much of the screen as possible.

// Fitting Aspc=0 means we fit no matter what the screen aspect ratio
Aspc=0,

// Scale to fit screen
A0="1.53",  // X scaling, smaller A0 => wider fractal
A1="0.89",  // Y scaling, smaller A1 => taller fractal
A2="2*a0*a1",

// Normal orientation would be like this
srcX="(sqr(a0*x) - sqr(a1*y) - 0.74543)/a0",
srcY="(a2*x*y + 0.11301)/a1",

// Flip X and Y if aspect ratio is wrong
//srcY="(sqr(a1*y) - sqr(a0*x) - 0.74543)/a1",
//srcX="(a2*x*y + 0.11301)/a0",

// The sign reversal above (i.e. subtracting 0.74543 instead of adding)
// is necessary because we're running the Julia set backwards.

Vers=100