Is this the correct topology?

Question

3D

Greetings.

Is such a construction (see screenshot 1) correct when there is only one face on the straight line and on the right side?



Or should it be done only this way (see screenshot 2)?



Or at least like this (see screenshot 3)?



Thanks in advance.

Answer 1

Of course, there are nuances and exceptions, but the general rule is this: in most cases, the topology of quadrilaterals is correct, sometimes triangles are acceptable, if there is no way without them.
In your case, in example 1, what you called "only one face" is essentially an octagon. The fact that the vertices (corners) are located on the same straight line does not change anything. Therefore, you need to do as in 2, and for 3 there must be good reasons.