Function greens_function_gradient_3d 

pub fn greens_function_gradient_3d(
    source: &Point,
    field: &Point,
    k: f64,
) -> [Complex64; 3]

Gradient of 3D Green’s function ∇_y G

∇_y G = (ik - 1/r) * G * (y - x)/r

Arguments

• source - Source point x
• field - Field point y
• k - Wave number

Returns

Complex 3-vector [∂G/∂y_x, ∂G/∂y_y, ∂G/∂y_z]