Question

I have 3 random points and need to order them counter-clockwise in relation to the normal of plane they form (one of them).

So the question is: I have the points, I have the normal – how do I order them counter clockwise?

I have seen this post on using polar form but am unsure if this is what I want and what point should I use.

Answer 1

If you haven’t picked a normal yet, then no matter what order you write three points in, they are ordered counter-clockwise (relative to a suitably chosen normal).

If you already have a normal (let’s call it n, and use a, b, c for the points), look at the sign of n*((b-a)x(c-a)). If it is positive, then (a,b,c) is counter-clockwise; if negative, (a,c,b).