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#include <stdint.h>
#include <inttypes.h>
#include <math.h>
#include <stdlib.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? */
typedef struct julia_context_t {
float rr;
float realscale;
float imagscale;
float creal;
float cimag;
float threshold;
unsigned n_cpus;
} julia_context_t;
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 void * julia_create_context(unsigned num_cpus)
{
return calloc(1, sizeof(julia_context_t));
}
static void julia_destroy_context(void *context)
{
free(context);
}
static inline unsigned julia_iter(float real, float imag, float creal, float cimag, unsigned max_iters, float threshold)
{
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) > threshold)
return i;
real = newr;
imag = newi;
}
return 0;
}
static int julia_fragmenter(void *context, const fb_fragment_t *fragment, unsigned num, fb_fragment_t *res_fragment)
{
julia_context_t *ctxt = context;
return fb_fragment_slice_single(fragment, ctxt->n_cpus, num, res_fragment);
}
/* Prepare a frame for concurrent drawing of fragment using multiple fragments */
static void julia_prepare_frame(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_fragmenter_t *res_fragmenter)
{
julia_context_t *ctxt = context;
*res_fragmenter = julia_fragmenter;
ctxt->n_cpus = n_cpus;
ctxt->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.
*/
ctxt->realscale = 0.01f * cosf(ctxt->rr) + 0.01f;
ctxt->imagscale = 0.01f * sinf(ctxt->rr * 3.0f) + 0.01f;
ctxt->creal = (1.01f + (ctxt->realscale * cosf(1.5f * M_PI + ctxt->rr) + ctxt->realscale)) * cosf(ctxt->rr * .3f);
ctxt->cimag = (1.01f + (ctxt->imagscale * sinf(ctxt->rr * 3.0f) + ctxt->imagscale)) * sinf(ctxt->rr);
/* Vary the divergent threshold, this has been tuned to dwell around 1 a bit since it's
* quite different looking, then shoot up to a very huge value approaching FLT_MAX which
* is also interesting.
*/
ctxt->threshold = cosf(M_PI + ctxt->rr * .1f) * .5f + .5f;
ctxt->threshold *= ctxt->threshold * ctxt->threshold;
ctxt->threshold *= 35.f;
ctxt->threshold = powf(10.f, ctxt->threshold);
}
/* Draw a morphing Julia set */
static void julia_render_fragment(void *context, unsigned cpu, fb_fragment_t *fragment)
{
julia_context_t *ctxt = context;
unsigned x, y;
unsigned 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, ctxt->creal, ctxt->cimag, sizeof(colors) / sizeof(*colors), ctxt->threshold)];
}
buf = ((void *)buf) + fragment->stride;
}
}
rototiller_module_t julia_module = {
.create_context = julia_create_context,
.destroy_context = julia_destroy_context,
.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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