Function normalise

pub fn normalise(a: &Vector3d, min_sq_value: f64) -> Option<Vector3d>

Normalize a vector to lie on the surface of the unit sphere.

Note: this function returns an Option so uses the British spelling of normalise to differentiate it from the standard normalize function.

• a the Vector3d
• min_sq_value the minimum square of a vector length to normalize.

return the nomalized point or None if the vector is too small to normalize.