Delphi

program Simple3d;

type
   T3dPoint=record
    x,y,z:real;
   end;
     
   T2dPoint=record
    x,y:real;
   end;

var fx,fy,fz:real;

function Round(x:real):integer;
begin
   Round:=Trunc(x);
   if ((Trunc(x)+0.5)<x) then
    Round:=Trunc(x)+1;
end;

function GetScreenProection(P:T3dPoint):T2dPoint;
var buf:T2dPoint;
begin
   buf.x:=fx-fz*(P.x-fx)/(P.z-fz);
   buf.y:=fy-fz*(P.y-fy)/(P.z-fz);
   GetScreenProection:=buf;
end;

procedure ClearDevice;
begin
   SetColor(0,0,0);
   FillRect(0,0,GetWidth,GetHeight);
end;

procedure Line(A,B:T2dPoint);
begin
   DrawLine(Round(A.x),
            Round(A.y),
            Round(B.x),
            Round(B.y));
end;

procedure Line3d(A,B:T3dPoint);
begin
   Line(GetScreenProection(A), GetScreenProection(B));
end;

function Rotation(X,O:T3dPoint; alpha, beta:real):T3dPoint;
var   
   vector:T3dPoint;
   buf:T3dPoint;
begin
   vector.x:=X.x-O.x;
   vector.y:=X.y-O.y;
   vector.z:=X.z-O.z;
     
   buf.x:=O.x+cos(alpha)*vector.x+sin(alpha)*vector.z;
   buf.y:=O.y+vector.y;
   buf.z:=O.z-sin(alpha)*vector.x+cos(alpha)*vector.z;

   vector.x:=buf.x-O.x;
   vector.y:=buf.y-O.y;
   vector.z:=buf.z-O.z;

   buf.x:=O.x+vector.x;
   buf.y:=O.y+cos(beta)*vector.y-sin(beta)*vector.z;
   buf.z:=O.z+sin(beta)*vector.y+cos(beta)*vector.z;
     
   Rotation:=buf;
end;

const pause=50;

var
   x_angle,
   y_angle:real;
   i,j:integer;
   A,B,C,D,O:T3dPoint;

begin
   x_angle:=Pi/30;
   y_angle:=-Pi/40;
     
   O.x:=GetWidth div 2;
   O.y:=GetHeight div 2;
   O.z:=60;
     
   fx:=O.x;
   fy:=O.y;
   fz:=-800;
     
   A.x:=O.x;      A.y:=O.y-50; A.z:=O.z;
   B.x:=O.x-41;   B.y:=O.y+17; B.z:=O.z-28;
   C.x:=O.y+41;   C.y:=O.y+17; C.z:=O.z-28;
   D.x:=O.x;      D.y:=O.y+17; D.z:=O.z+56;
     
   repeat
     ClearDevice;
//   SetColor(255,0,0);
//   Line3d(O,A);
//   Line3d(O,B);
//   Line3d(O,C);
//   Line3d(O,D);    
     SetColor(0,255,0);
     Line3d(A,B);
     Line3d(A,C);
     Line3d(A,D);
     Line3d(B,C);
     Line3d(C,D);
     Line3d(D,B);
      
     A:=Rotation(A,O,x_angle,y_angle);
     B:=Rotation(B,O,x_angle,y_angle);
     C:=Rotation(C,O,x_angle,y_angle);
     D:=Rotation(D,O,x_angle,y_angle);
       
    Repaint;
    Delay(pause);
   until false;
     
end.