Actually, you must have Do you know ahead of time when you need the positive and when you need the negative?
I'm trying to find the z component of a unit normal of a plane given the x and y components.
Since it's a unit normal I know that I have , therefore, .
This seems fine in testing, until a case where should be negative, at which point the world breaks! Am I doing something stupid here? It's worth mentioning that I'm doing this as part of an image-plane to world-plane correction and as such don't have any coordinates of points on the world-plane itself. The only information I have is a set of image-plane coordinates.
Sorry, I forgot the +/-. I don't unfortunately, this is my problem. I was wondering if there was some way I'd missed to determine the sign.
Given that I'm going to be using Broyden's method to approximate and as well as 2 other variables, I starting to think it might just be worth putting in as a 5th variable to approximate.