X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;f=src%2Fscr%2Ffract.c;fp=src%2Fscr%2Ffract.c;h=6eeb6787611475468edfa3e68593674f335184a5;hb=ba648ddfc62fc6d3f47294aa8bfc10ea6ca3f479;hp=0000000000000000000000000000000000000000;hpb=3398fc6c4188104048f99b650a6cb90beda9b6ed;p=dosdemo

diff --git a/src/scr/fract.c b/src/scr/fract.c
new file mode 100644
index 0000000..6eeb678
--- /dev/null
+++ b/src/scr/fract.c
@@ -0,0 +1,95 @@
+#include <string.h>
+#include <limits.h>
+#include "demo.h"
+#include "screen.h"
+#include "gfxutil.h"
+
+struct vec2x {
+	long x, y;
+};
+
+static int init(void);
+static void destroy(void);
+static void draw(void);
+static int julia(long x, long y, long cx, long cy, int max_iter);
+
+static struct screen scr = {
+	"fract",
+	init,
+	destroy,
+	0, 0,
+	draw
+};
+
+/*static long aspect_24x8 = (long)(1.3333333 * 256.0);*/
+static long xscale_24x8 = (long)(1.3333333 * 1.2 * 256.0);
+static long yscale_24x8 = (long)(1.2 * 256.0);
+static int cx, cy;
+static int max_iter = 50;
+
+#define WALK_SIZE	20
+
+struct screen *fract_screen(void)
+{
+	return &scr;
+}
+
+static int init(void)
+{
+	return 0;
+}
+
+static void destroy(void)
+{
+}
+
+static void draw(void)
+{
+	int i, j;
+	unsigned short *pixels = fb_pixels;
+
+	cx = mouse_x;
+	cy = mouse_y;
+
+	for(i=0; i<fb_height; i++) {
+		for(j=0; j<fb_width; j++) {
+			unsigned char pidx = julia(j, i, cx, cy, max_iter) & 0xff;
+			*pixels++ = (pidx >> 3) | ((pidx >> 2) << 5) | ((pidx >> 3) << 11);
+		}
+	}
+
+	pixels = fb_pixels;
+	pixels[mouse_y * fb_width + mouse_x] = 0xffe;
+	swap_buffers(0);
+}
+
+static long normalize_coord(long x, long range)
+{
+	/* 2 * x / range - 1*/
+	return (x << 17) / range - 65536;
+}
+
+static int julia(long x, long y, long cx, long cy, int max_iter)
+{
+	int i;
+
+	/* convert to fixed point roughly [-1, 1] */
+	x = (normalize_coord(x, fb_width) >> 8) * xscale_24x8;
+	y = (normalize_coord(y, fb_height) >> 8) * yscale_24x8;
+	cx = (normalize_coord(cx, fb_width) >> 8) * xscale_24x8;
+	cy = (normalize_coord(cy, fb_height) >> 8) * yscale_24x8;
+
+	for(i=0; i<max_iter; i++) {
+		/* z_n = z_{n-1}**2 + c */
+		long px = x >> 8;
+		long py = y >> 8;
+
+		if(px * px + py * py > (4 << 16)) {
+			break;
+		}
+		x = px * px - py * py + cx;
+		y = (px * py << 1) + cy;
+	}
+
+	return i < max_iter ? (256 * i / max_iter) : 0;
+}