Mmm, the reference of sub() isn't very clear, mixing two or three versions, letting the reader to guess what returns "none" and what returns a PVector.
loc_2[i].sub(loc_2[i+1]) just alters the first first vector by subtracting the second one.
If you don't want to change them, you have to use the static version: PVector perp0 = PVector.sub(loc_2[i], loc_2[i+1]);

Hi,

cross() doesn't have a static version (used with PVector instead of an instance of this class). What is wrong with your first version? Why are you trying the second one?

I guess the error you might have with first version is cannot convert from void to PVector.
That is because normalize() without any parameters will return void.
And you are expecting to have a PVector to store in perp1.

For the second version phi.lho is right.
You can't call cross() as a static method, so PVector.cross(...) will not work.

So, you could split your assignment in two lines like :

1. PVector perp1 = perp0.cross(new PVector(0, 1, 0));
2. perp1.normalize();

OR if you want just one line, use the normalize(PVector) method which returns a PVector :

1. PVector perp1 = (perp0.cross(new PVector(0, 1, 0))).normalize(null);

You can have a look at the PVector source.