[thaumasiotes]

> G2 tangential: same as G1, but the surfaces are tangential

This makes me think "tangential to what?".

Do you mean that, along the seam between G1 and G2, the tangent plane to G1 at a given point is equal to the tangent plane to G2 at the same point?

[swimfar]

Here's a good visual explanation: https://blogs.lt.vt.edu/2ndyearidlab/author/hohsuan/page/2/

[avianlyric]

Yep, exactly that. Removes the appearance of a “fold” or “crease” at the surface transition, and makes the surface smooth and continuous.