spectrum_cmbrot
view test.c @ 0:e56d8b0eee4b
spectrum fractal :)
| author | John Tsiombikas <nuclear@member.fsf.org> |
|---|---|
| date | Mon, 17 Feb 2014 10:17:17 +0200 |
| parents | |
| children | c2815c765fea |
line source
1 #define FB_ADDR ((unsigned char*)0x4000)
2 #define ATTR_ADDR ((unsigned char*)0x5800)
3 #define LINESKIP (256 / 8)
5 unsigned char mbrot(int px, int py);
7 int main()
8 {
9 unsigned int i, j, k, start;
11 for(;;) {
12 start = 0;
14 for(i=0; i<192; i++) {
15 unsigned int banky = i & 0x3f;
16 unsigned int cell = banky / 8;
17 unsigned int cline = banky % 8;
18 unsigned int memline = cell + cline * 8;
19 unsigned char *ptr = FB_ADDR + (start + memline) * LINESKIP;
21 for(j=0; j<32; j++) { /* 256 pixels, 8 pixels per byte */
22 unsigned char pixel = 0;
23 for(k=0; k<8; k++) {
24 unsigned char res = mbrot((j << 3) + k, i);
25 pixel = pixel | (res & 1);
26 if(k < 7) pixel <<= 1;
27 }
28 *ptr++ = pixel;
29 }
31 if((i & 0x3f) == 0x3f) {
32 start += 0x40;
33 }
34 }
35 }
36 }
38 #define int2fix8_8(i) ((i) << 8)
39 #define fix_mul8_8(a, b) ((a >> 4) * (b >> 4))
40 #define int2fix5_11(i) ((i) << 11)
41 #define fix_mul5_11(a, b) ((a >> 5) * (b >> 6))
43 unsigned char mbrot(int px, int py)
44 {
45 unsigned char i;
46 int cx, cy, zx, zy, x, y, len;
48 cx = int2fix8_8(px - 192) >> 6;
49 cy = int2fix8_8(py - 96) >> 6;
51 cx <<= 3;
52 cy <<= 3;
54 zx = cx;
55 zy = cy;
57 for(i=0; i<32; i++) {
58 x = fix_mul5_11(zx, zx) - fix_mul5_11(zy, zy) + cx;
59 y = fix_mul5_11(zy, zx) + fix_mul5_11(zx, zy) + cy;
60 len = fix_mul5_11(x, x) + fix_mul5_11(y, y);
62 if(len > int2fix5_11(4)) return 0;
64 zx = x;
65 zy = y;
66 }
68 return 1;
69 }