Asymptotic self-similarity
The Mandelbrot is asymptotically self-similar about pre-periodic Misiurewicz points. The derivative of the cycle (with respect to \(z\)) can be used as a multiplier for seamlessly looping zoom animations. Here are some examples:
const dvec2 c0 = dvec2(-0.22815549365396179LF, 1.1151425080399373LF); const int pre = 3; const int per = 1;
const dvec2 c0 = dvec2(-0.10109636384562216LF, 0.9562865108091415LF); const int pre = 4; const int per = 3;
(The above example's Misiurewicz point has period 1, but using 3 here avoids rapid spinning.)
const dvec2 c0 = dvec2(-0.77568377LF, 0.13646737LF); const int pre = 24; const int per = 2;
Here is the rest of the code that made the images, it's for Fragmentarium with
my (as yet unreleased, but coming soon) Complex.frag
enhancements
for dual-numbers and double-precision:
#version 400 core #include "Complex.frag" #include "Progressive2D.frag" uniform float time; // insert snippets from above in here to choose image const double r0 = 0.00001LF; vec3 color(vec2 p) { // calculate multiplier for zoom dvec4 z = cVar(0.0LF); dvec4 c = cConst(c0); for (int i = 0; i < pre; ++i) z = cSqr(z) + c; z = cVar(cVar(z)); for (int i = 0; i < per; ++i) z = cSqr(z) + c; dvec2 m = r0 * dvec2(cPow(vec2(cInverse(cDeriv(z))), mod(time, float(per)) / float(per))); const int maxiters = 1000; const double er2 = 1000.0LF; c = cVar(c0 + cMul(m, p)); z = cConst(0.0LF); double pixelsize = cAbs(m) * double(length(vec4(dFdx(p), dFdy(p)))); int i; for (i = 0; i < maxiters; ++i) { z = cSqr(z) + c; if (cNorm(z) > er2) { break; } } if (i == maxiters) { return vec3(1.0, 0.7, 0.0); } else { double de = 2.0 * cAbs(z) * double(log(float(cAbs(z)))) / cAbs(cDeriv(z)); float grey = tanh(clamp( float(de/pixelsize), 0.0, 8.0 )); return vec3(grey); } }