Find vector closest to X_AXIS

[thomthom]

With a given set of various vectors, how do you determine which one is the one most parallel to another, say the X_AXIS?

[avariant]

take the dot product of each vector, normalized, with the vector you are comparing against, normalized.

how_close = vector_a.normalize().dot( comparison_axis )
how_close_b = vector_b.normalize().dot( comparison_axis )

the normalize is important because they all need to be the same length for this kind of comparison.

[thomthom]

Does the direction of the vector matter then?

[avariant]

Oops sorry. Meant to tack that on.

dot product = 1 means parallel and in the same direction
dot product = -1 means parallel and in the opposite direction.

So if direction matters, look for closest to 1. If it doesn't, use the absolute value.

[thomthom]

Great! Thank you very much!