BabaMara - 1 year ago 101
C++ Question

# Calculation of euler angles

I need help understanding the math behind this code. x component of the returned vec2 and the y component of the returned vec2. Can somebody explain to me what they represent. I only know this function determinate the position of the vector in sphere coordinates.

``````glm::vec2 calcEulerAngles(const glm::vec3& vec)
{
glm::vec3 v = glm::normalize(vec);
glm::vec2 result(acos(v.z), atan2(v.y, v.x));
while (result.y < 0.0)
result.y += TwoPi;

return glm::vec2(glm::degrees(result.x), glm::degrees(result.y));
}
``````

It is calculating the spherical coordinates `phi` and `theta` for a unit vector.
The first component (`phi`) will be the angle between the vector and the z-axis. The second component (`theta`) will be the angle on the xy-plane. It assumes that the vector can be expressed as follows:
``````x = cos theta sin phi
If you solve this, you get the calculations in your function. Adding `2 Pi` to `y` just ensures that the angle is between `0` and `2 Pi`.