donut.R

                ts=0.07;ps=0.02;A=B=0;
            while(1){ j=i=0;z=rep(0,1760);
          b=rep(' ',1760); while(j < 6.28){
         j=j+ts;i=0;while(i<6.28){i=i+ps;c=
        sin(i);l=cos(i);      d=cos(j);f=sin(j);
      e=sin(A);g=cos(A         );h=d+2;D=1/(c*h*e+
     f*g+5);m=cos(B)            ;n=sin(B);t=c*h*g-
     f*e;x=as.integer           (40+30*D*(l*h*m-t*n));
    y=as.integer(12+            15*D*(l*h*n+t*m));
    o=as.integer(x+(            80*y));N=as.integer(
    8*((f*e-c*d*g)*m-           c*d*e-f*g-l*d*n));st=
    c('.',',','-','~',          ':',';','=','!','*',
     '#','$','@');if(22>    y&&y>0&&80  >x&&x>0&&
      D>z[o]){z[o]=D;b[o]=st[ifelse(N>0,N,1)]}}};
       lines=apply(matrix(b,ncol=80,byrow=T),1,
         paste,collapse="");cat("\014");cat(
           '\x1b[H');for(ll in seq_along(
             lines)){cat(lines[ll],"\n")}
                  A=A+0.04;B=B+0.02}

donut_expanded.R

donut <- function(frames=Inf) {
  ts <- 0.07
  ps <- 0.02
  A <- 0
  B <- 0
  ff <- 0
  while (ff <= frames) {
    ff <- ff + 1
    j <- i <- 0
    z <- rep(0, 1760)
    b <- rep(' ', 1760)
    while (j < 6.28) {
      j <- j + ts
      i <- 0
      while (i < 6.28) {
        i <- i + ps
        c <- sin(i)
        l <- cos(i)
        d <- cos(j)
        f <- sin(j)
        e <- sin(A)
        g <- cos(A)
        h <- d+2
        D <- 1/(c*h*e+f*g+5)
        m <- cos(B)
        n <- sin(B)
        t <- c*h*g-f*e
        x <- as.integer(40+30*D*(l*h*m-t*n))
        y <- as.integer(12+15*D*(l*h*n+t*m))
        o <- as.integer(x+(80*y))
        N <- as.integer(8*((f*e-c*d*g)*m-c*d*e-f*g-l*d*n))
        st <- c('.',',','-','~',':',';','=','!','*','#','$','@')
        if (22 > y && y > 0 && 80 > x && x > 0 && D > z[o]) {
          z[o] <- D
          b[o] <- st[ifelse(N > 0, N, 1)]
        } 
      }
    }
    lines <- apply(matrix(b, ncol=80, byrow = T), 1, paste, collapse = "")
    cat("\014")
    cat('\x1b[H')
    for (ll in seq_along(lines)) {
      cat(lines[ll], "\n")
    }
    A <- A + 0.04
    B <- B + 0.02
  }
}

donut()