= General conical surface
{title2=$S(s,t)=A+tD(s)$}
A general conical surface is swept out by straight generators through one apex $A$. An invertible <affine map> sends it to another such surface, since it sends each generator to a line through the transformed apex. A <projective transformation> preserves the projective concurrence of generators, but can send the apex to infinity, producing parallel generators in the affine chart. Therefore finite-apex cones and cylinders are not separately projectively invariant Euclidean classes.
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