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68 lines
1.8 KiB
C++
68 lines
1.8 KiB
C++
// The donut code with fixed-point arithmetic; no sines, cosines, square roots, or anything.
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// a1k0n 2020
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// Code from: https://gist.github.com/a1k0n/80f48aa8911fffd805316b8ba8f48e83
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// For more info:
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// - https://www.a1k0n.net/2011/07/20/donut-math.html
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// - https://www.youtube.com/watch?v=DEqXNfs_HhY
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <libbase/console.h>
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#define R(mul,shift,x,y) \
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_=x; \
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x -= mul*y>>shift; \
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y += mul*_>>shift; \
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_ = (3145728-x*x-y*y)>>11; \
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x = x*_>>10; \
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y = y*_>>10;
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signed char b[1760], z[1760];
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void donut(void) {
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int sA=1024,cA=0,sB=1024,cB=0,_;
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for (;;) {
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memset(b, 32, 1760); // text buffer
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memset(z, 127, 1760); // z buffer
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int sj=0, cj=1024;
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for (int j = 0; j < 90; j++) {
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int si = 0, ci = 1024; // sine and cosine of angle i
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for (int i = 0; i < 324; i++) {
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int R1 = 1, R2 = 2048, K2 = 5120*1024;
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int x0 = R1*cj + R2,
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x1 = ci*x0 >> 10,
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x2 = cA*sj >> 10,
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x3 = si*x0 >> 10,
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x4 = R1*x2 - (sA*x3 >> 10),
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x5 = sA*sj >> 10,
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x6 = K2 + R1*1024*x5 + cA*x3,
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x7 = cj*si >> 10,
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x = 40 + 30*(cB*x1 - sB*x4)/x6,
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y = 12 + 15*(cB*x4 + sB*x1)/x6,
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N = (((-cA*x7 - cB*((-sA*x7>>10) + x2) - ci*(cj*sB >> 10)) >> 10) - x5) >> 7;
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int o = x + 80 * y;
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signed char zz = (x6-K2)>>15;
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if (22 > y && y > 0 && x > 0 && 80 > x && zz < z[o]) {
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z[o] = zz;
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b[o] = ".,-~:;=!*#$@"[N > 0 ? N : 0];
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}
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R(5, 8, ci, si) // rotate i
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}
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R(9, 7, cj, sj) // rotate j
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}
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for (int k = 0; 1761 > k; k++)
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putchar(k % 80 ? b[k] : 10);
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R(5, 7, cA, sA);
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R(5, 8, cB, sB);
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if (readchar_nonblock()) {
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getchar();
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break;
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}
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fputs("\x1b[23A", stdout);
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}
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}
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