Using atan2 to find angle between two vectors
geometry, math, vector
Solution
atan2(vector1.y - vector2.y, vector1.x - vector2.x)
is the angle between the difference vector (connecting vector2 and vector1) and the x-axis, which is problably not what you meant.
The (directed) angle from vector1 to vector2 can be computed as
angle = atan2(vector2.y, vector2.x) - atan2(vector1.y, vector1.x);
and you may want to normalize it to the range [0, 2 π):
if (angle < 0) { angle += 2 * M_PI; }
or to the range (-π, π]:
if (angle > M_PI) { angle -= 2 * M_PI; }
else if (angle <= -M_PI) { angle += 2 * M_PI; }
Problem
I understand that: `atan2(vector.y, vector.x)` = the angle between the vector and the X axis. But I wanted to know how to get the angle between two vectors using atan2. So I came across this solution: ``` atan2(vector1.y - vector2.y, vector1.x - vector2.x) ``` My question is very simple: Will the two following formulas produce the same number? `atan2(vector1.y - vector2.y, vector1.x - vector2.x)` `atan2(vector2.y - vector1.y, vector2.x - vector1.x)` If not: How do I know what vector comes first in the subtractions?