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#include <stdint.h>
#include <inttypes.h>
#include <math.h>
#include "fb.h"
#include "rototiller.h"
/* Copyright (C) 2017 Vito Caputo <vcaputo@pengaru.com> */
/* Julia set renderer - see https://en.wikipedia.org/wiki/Julia_set, morphing just means to vary C. */
/* TODO: explore using C99 complex.h and its types? */
static inline unsigned julia_iter(float real, float imag, float creal, float cimag, unsigned max_iters)
{
unsigned i;
float newr, newi;
for (i = 1; i < max_iters; i++) {
newr = real * real - imag * imag;
newi = imag * real;
newi += newi;
newr += creal;
newi += cimag;
if ((newr * newr + newi * newi) > 4.0)
return i;
real = newr;
imag = newi;
}
return 0;
}
/* Draw a morphing Julia set */
static void julia(fb_fragment_t *fragment)
{
static uint32_t colors[] = {
/* this palette is just something I slapped together, definitely needs improvement. TODO */
0x000000,
0x000044,
0x000088,
0x0000aa,
0x0000ff,
0x0044ff,
0x0088ff,
0x00aaff,
0x00ffff,
0x44ffaa,
0x88ff88,
0xaaff44,
0xffff00,
0xffaa00,
0xff8800,
0xff4400,
0xff0000,
0xaa0000,
0x880000,
0x440000,
0x440044,
0x880088,
0xaa00aa,
0xff00ff,
0xff4400,
0xff8800,
0xffaa00,
0xffff00,
0xaaff44,
0x88ff88,
0x44ffaa,
0x00ffff,
0x00aaff,
0x0088ff,
0xff4400,
0xff00ff,
0xaa00aa,
0x880088,
0x440044,
};
static float rr;
unsigned x, y;
unsigned stride = fragment->stride / 4, width = fragment->width, height = fragment->height;
uint32_t *buf = fragment->buf;
float real, imag;
float realstep = 3.6f / (float)width, imagstep = 3.6f / (float)height;
/* Rather than just sweeping creal,cimag from -2.0-+2.0, I try to keep things confined
* to an interesting (visually) range. TODO: could certainly use refinement.
*/
float realscale = 0.01f * cosf(rr) + 0.01f;
float imagscale = 0.01f * sinf(rr * 3.0f) + 0.01f;
float creal = (1.01f + (realscale * cosf(1.5f*M_PI+rr) + realscale)) * cosf(rr * .3f);
float cimag = (1.01f + (imagscale * sinf(rr * 3.0f) + imagscale)) * sinf(rr);
/* Complex plane confined to {-1.8 - 1.8} on both axis (slightly zoomed), no dynamic zooming is performed. */
for (imag = 1.8, y = 0; y < height; y++, imag += -imagstep) {
for (real = -1.8, x = 0; x < width; x++, buf++, real += realstep) {
*buf = colors[julia_iter(real, imag, creal, cimag, sizeof(colors) / sizeof(*colors))];
}
buf += stride;
}
rr += .01;
}
rototiller_renderer_t julia_renderer = {
.render = julia,
.name = "julia",
.description = "Julia set fractal morpher",
.author = "Vito Caputo <vcaputo@pengaru.com>",
.license = "GPLv2",
};
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