Set the IOR to 1.0 and render. The torus is gone! This is
because no rays get bent with this IOR value. Because
fresnel IOR is linked to the refraction IOR, this is also
set to 1.0, which means the object becomes non reflec-
tive too. The refraction color is pure white, so the rays
don’t become tinted either! All this makes the torus
disappear.