/// The encoding used for a voxel-position block.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum PositionEncoding {
/// One `[x, y, z]` triple per voxel.
RawJson,
/// Dense occupancy bitmap over `bounds`, base64-encoded.
BitmapBase64,
/// Prefix-sum deltas of each voxel's 3D Hilbert index,
/// varint+base64-encoded.
Hilbert,
}