Why vertex normal points downward in this case?

[Quan_Li]

Vertex Normal not right.gh (16.0 KB)

I have been thinking vertex normal is an average vector of all adjacent face normals.

[HS_Kim]

Some of the Z vectors from Is Planarhave been flipped somehow…I’m not sure if this is a bug or not.
Anyway, you could use normal vectors from Face Normals instead.

Vertex Normal not right._re.gh (14.9 KB)

[Quan_Li]

Thank you very much! I understand it now.