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-rw-r--r--src/modules/julia/julia.c117
1 files changed, 117 insertions, 0 deletions
diff --git a/src/modules/julia/julia.c b/src/modules/julia/julia.c
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+++ b/src/modules/julia/julia.c
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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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