Ver 3. << Display three balls.

Ver 3. << Display three balls.
mat4 ModelMatrix3 = translate(mat4(1.0),vec3(0.0,0.5,0.0));
wrong:
mat4 ModelMatrix3 = translate(mat4(1.0),vec3(0.0,0.5,-0.5));
If the z coordinate is smaller than zero, the ball cannot be seen.