Normal per vertex when re-using vertices

I am making an addon to create this type of primitive in openFrameworks https://threejs.org/docs/#api/en/geometries/LatheGeometry

Let’s say that I want to create a mesh, where the triangles composing it are re-using some vertices.
So, instead of having 9 vertices as in the left side of the picture, I have 5, as in the right side of the picture.

image

Let’s also say that this triangle strip does not lay on a flat plane, where all the normals look in the same direction, but it covers a curved surface, like in the Lathe Geometry in the threejs example.

I assume that the normal for the vertex C in the picture on the left is just an interpolation between the normal of A and the normal of E, and I think this is what is happening in threejs https://github.com/mrdoob/three.js/blob/master/src/geometries/LatheGeometry.js#L166.
Is this the way to go? are there any complication that could arise, whenever I want to make the geometries created by this addon instance of a class that inherits from ofPrimitive? ofBoxPrimitive, for example, is not re-using vertices.

In general I am wondering about any complication of having a mesh that re-use vertices and has interpolated normals, and I am considering of keeping things simpler and go for the classical approach on the left side of the image.

That’s fine as long as you don’t need flat shading or different texturing for the different faces…

ok, got it, thanks. Flat shading and different texture per triangles is definitely something that I do not want.