c = cos(45*pi/180);
s = sin(45*pi/180);
Rz45 = [c,s,0,0;-s,c,0,0;0,0,1,0;0,0,0,1];
c = cos(20*pi/180);
s = sin(20*pi/180);
Ry20 = [c,0,-s,0;0,1,0,0;s,0,c,0;0,0,0,1];
Tdisp = Ry20' * Rz45;

t = [0:0.01:1];
y = t;
r = (0.25 - (y-0.5).^2) .^ 0.5;
x = r .* cos(10*pi*t);
z = r .* sin(10*pi*t);
BALL = [x;y;z;x.^0];


c = cos(1*pi/180);
s = sin(1*pi/180);
Rx = [1,0,0,0;0,c,s,0;0,-s,c,0;0,0,0,1];
Ry = [c,0,-s,0;0,1,0,0;s,0,c,0;0,0,0,1];
Rz = [c,s,0,0;-s,c,0,0;0,0,1,0;0,0,0,1];



I = eye(4,4);
T = eye(4,4);
for i=1:10000
   T(3,4) = 0;
   T = Rz*T;
   T(3,4) = sin(i*0.01);
   Display3D(T*BALL, Tdisp);
   pause(0.01);
   end