donut/donut.c

/**
 * Original author:
 * https://twitter.com/a1k0n
 * https://www.a1k0n.net/2021/01/13/optimizing-donut.html
 *
 * Change Logs:
 * Date           Author       Notes
 * 2006-09-15     Andy Sloane  First version
 * 2011-07-20     Andy Sloane  Second version
 * 2021-01-13     Andy Sloane  Third version
 * 2021-03-25     Meco Man     Port to RT-Thread RTOS
 */

#include <rtthread.h>

#define R(mul,shift,x,y) \
    _=x; \
    x -= mul*y>>shift; \
    y += mul*_>>shift; \
    _ = 3145728-x*x-y*y>>11; \
    x = x*_>>10; \
    y = y*_>>10;

void donut(void)
{
    int sA=1024,cA=0,sB=1024,cB=0,_;
    rt_int8_t *b = rt_malloc(1760 * sizeof(rt_int8_t));
    if(b == RT_NULL)
    {
        return;
    }

    rt_int8_t *z = rt_malloc(1760 * sizeof(rt_int8_t));
    if(z == RT_NULL)
    {
        rt_free(b);
        return;
    }

    rt_kprintf("\033[?25l"); // hide cursor
    rt_kprintf("Have a donut!\r\n");

    while(1)
    {
        rt_memset(b, 32, 1760);  // text buffer
        rt_memset(z, 127, 1760);   // z buffer
        int sj=0, cj=1024;
        for (int j = 0; j < 90; j++)
        {
            int si = 0, ci = 1024;  // sine and cosine of angle i
            for (int i = 0; i < 324; i++)
            {
                int R1 = 1, R2 = 2048, K2 = 5120*1024;

                int x0 = R1*cj + R2,
                    x1 = ci*x0 >> 10,
                    x2 = cA*sj >> 10,
                    x3 = si*x0 >> 10,
                    x4 = R1*x2 - (sA*x3 >> 10),
                    x5 = sA*sj >> 10,
                    x6 = K2 + R1*1024*x5 + cA*x3,
                    x7 = cj*si >> 10,
                    x = 40 + 30*(cB*x1 - sB*x4)/x6,
                    y = 12 + 15*(cB*x4 + sB*x1)/x6,
                    N = (-cA*x7 - cB*((-sA*x7>>10) + x2) - ci*(cj*sB >> 10) >> 10) - x5 >> 7;

                int o = x + 80 * y;
                rt_int8_t zz = (x6-K2)>>15;
                if (22 > y && y > 0 && x > 0 && 80 > x && zz < z[o])
                {
                    z[o] = zz;
                    b[o] = ".,-~:;=!*#$@"[N > 0 ? N : 0];
                }
                R(5, 8, ci, si)  // rotate i
            }
            R(9, 7, cj, sj)  // rotate j
        }
        for (int k = 0; 1761 > k; k++)
        {
            rt_kprintf("%c",(k % 80 ? b[k] : 10));
        }
        R(5, 7, cA, sA);
        R(5, 8, cB, sB);
        rt_schedule();
        rt_kprintf("\x1b[23A");
    }
}
MSH_CMD_EXPORT(donut, a 3D spinning donut);