Function expect_quat

perro_source/core/perro_animation/src/panim/fields.rs:446–462

(value: &SceneValue, key: &str, line_no: usize)

        .ok_or_else(|| format!("line {}: `{}` expects vec3", line_no, key))?;
    Ok(Vector3::new(x, y, z))
}

fn expect_color3(value: &SceneValue, key: &str, line_no: usize) -> Result<[f32; 3], String> {
    let (x, y, z) = value
        .as_vec3()
        .ok_or_else(|| format!("line {}: `{}` expects vec3", line_no, key))?;
    Ok([x, y, z])
}

fn expect_quat(value: &SceneValue, key: &str, line_no: usize) -> Result<Quaternion, String> {
    if let Some((x, y, z, w)) = value.as_vec4() {
        let mut quat = Quaternion::new(x, y, z, w);
        quat.normalize();
        return Ok(quat);
    }

    // Keep parity with scene parser behavior: Node3D rotation accepts Euler XYZ radians.
    if let Some((x, y, z)) = value.as_vec3() {
        let mut rotation = Quaternion::IDENTITY;
        rotation.rotate_xyz(x, y, z);