Function encode_direction 

pub fn encode_direction(dir: &[f64; 3], n_freq: usize) -> Vec<f64>

Encode a unit viewing-direction vector with n_freq frequency bands per component.

Identical in structure to encode_position but intended for the lower-frequency direction branch of NeRF (typically n_freq = 4).

Output length: 3 * (1 + 2 * n_freq).

Arguments

• dir – unit-length view direction [dx, dy, dz].
• n_freq – number of frequency bands L.