uses graph, crt;
const grtegur=270.0;
keskx=300; kesky=250;

procedure keera(var x, y, z: real; xz, yz, xy: real);
var abi: real;
begin
    abi:=x;
    x:=round(x*cos(xz)-z*sin(xz));
    z:=round(abi*sin(xz)+z*cos(xz));
    abi:=y;
    y:=round(y*cos(yz)-z*sin(yz));
    z:=round(abi*sin(yz)+z*cos(yz));
    abi:=x;
    x:=round(x*cos(xy)-y*sin(xy));
    y:=round(abi*sin(xy)+y*cos(xy));
end;

procedure joonista_post(ax, ay, az, vx, vy, vz: real;
          xz, yz, xy: real);
   var n1x, n1y, n1z, n2x, n2y, n2z, abi: real;
   begin
    n1x:=ax-vx; n1y:=ay-vy; n1z:=az-vz;
    n2x:=n1x; n2y:=n1y-100; n2z:=n1z;
    keera(n1x, n1y, n1z, xz, yz, xy);
    keera(n2x, n2y, n2z, xz, yz, xy);
    if (n1z>0) and (n2z>0) then
    begin
      line(keskx+round(n1x*grtegur/n1z), kesky-round(n1y*grtegur/n1z),
            keskx+round(n2x*grtegur/n2z), kesky-round(n2y*grtegur/n2z));
      circle(keskx+round(n1x*grtegur/n1z), kesky-round(n1y*grtegur/n1z),
             round(20*grtegur/n1z));
    end;
   end;

procedure joonista_postid(vx, vy, vz:real; xz, yz, xy:real);
var kaugus: integer;
begin
 kaugus:=500;
 while(kaugus<2000)do
 begin
       joonista_post(-300, 100, kaugus, vx, vy, vz, xz, yz, xy);
       joonista_post( 100, 100, kaugus, vx, vy, vz, xz, yz, xy);
       kaugus:=kaugus+100;
 end;
end;

var d, m: integer;
 mx, my, mz: real; {vaataja koordinaadid}
 sxz, syz, sxy: real; {vaatenurk}
 c: char; samm:real;
begin
 d:=detect; initgraph(d, m, '');
 mx:=0; my:=0; mz:=0; samm:=5;
 sxz:=0; syz:=0; sxy:=0;
 outtextxy(5, 10, 'liigutamiseks klahvid k, j, l, h, i, m, tuhik');
 outtextxy(5, 20, 'keeramiseks   klahvid s, d, a, f, e, x');
 repeat
  joonista_postid(mx, my, mz, -sxz, -syz, -sxy);

  c:=readkey;
  case c of
    'k':mz:=mz+samm; 'j':mz:=mz-samm;
    'l':mx:=mx+samm; 'h':mx:=mx-samm;
    'i':my:=my+samm; 'm':my:=my-samm;
    'd':sxz:=sxz+0.01; 's':sxz:=sxz-0.01;
    'e':syz:=syz-0.01; 'x':syz:=syz+0.01;
    'f':sxy:=sxy+0.01; 'a':sxy:=sxy-0.01;
    ' ':begin
         mx:=mx-samm*sin(sxz);
         my:=my-samm*sin(syz)*cos(sxz);
         mz:=mz+samm*cos(syz)*cos(sxz);
        end;
  end;
  cleardevice;
 until c=chr(27);
 closegraph;
end.