Function spherical_to_cartesian

nodedb-codec/src/spherical.rs:195–233

Convert from spherical back to Cartesian coordinates.

(sph: &[f32])

/// Convert from spherical back to Cartesian coordinates.
fn spherical_to_cartesian(sph: &[f32]) -> Vec<f32> {
    let n = sph.len();
    if n == 0 {
        return Vec::new();
    }
    if n == 1 {
        return vec![sph[0]];
    }

    let r = sph[0];
    let angles = &sph[1..];
    let dims = n; // same dimensionality

    let mut cart = Vec::with_capacity(dims);

    for i in 0..dims - 1 {
        let mut val = r;
        for a in &angles[..i] {
            val *= a.sin();
        }
        if i < dims - 2 {
            val *= angles[i].cos();
        } else {
            // Second-to-last uses sin, last uses the atan2 angle.
            val *= angles[dims - 2].sin();
        }
        cart.push(val);
    }

    // Last coordinate.
    let mut val = r;
    for angle in &angles[..dims - 2] {
        val *= angle.sin();
    }
    val *= angles[dims - 2].cos();
    cart.push(val);

    cart
}

fn build_header(dims: u32, vectors: u32, transform: u8, compressed: &[u8]) -> Vec<u8> {
    let mut out = Vec::with_capacity(9 + compressed.len());