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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 float rr;
static float realscale;
static float imagscale;
static float creal;
static float cimag;
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;
}
/* Prepare a frame for concurrent drawing of fragment using multiple fragments */
static void julia_prepare_frame(unsigned n_cpus, fb_fragment_t *fragment, rototiller_frame_t *res_frame)
{
res_frame->n_fragments = n_cpus;
fb_fragment_divide(fragment, n_cpus, res_frame->fragments);
rr += .01;
/* 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.
*/
realscale = 0.01f * cosf(rr) + 0.01f;
imagscale = 0.01f * sinf(rr * 3.0f) + 0.01f;
creal = (1.01f + (realscale * cosf(1.5f*M_PI+rr) + realscale)) * cosf(rr * .3f);
cimag = (1.01f + (imagscale * sinf(rr * 3.0f) + imagscale)) * sinf(rr);
}
/* Draw a morphing Julia set */
static void julia_render_fragment(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,
};
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)fragment->frame_width, imagstep = 3.6f / (float)fragment->frame_height;
/* Complex plane confined to {-1.8 - 1.8} on both axis (slightly zoomed), no dynamic zooming is performed. */
for (imag = 1.8 + -(imagstep * (float)fragment->y), y = fragment->y; y < fragment->y + height; y++, imag += -imagstep) {
for (real = -1.8 + realstep * (float)fragment->x, x = fragment->x; x < fragment->x + width; x++, buf++, real += realstep) {
*buf = colors[julia_iter(real, imag, creal, cimag, sizeof(colors) / sizeof(*colors))];
}
buf += stride;
}
}
rototiller_module_t julia_module = {
.prepare_frame = julia_prepare_frame,
.render_fragment = julia_render_fragment,
.name = "julia",
.description = "Julia set fractal morpher (threaded)",
.author = "Vito Caputo <vcaputo@pengaru.com>",
.license = "GPLv2",
};
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