motedb 0.8.2

AI-native embedded multimodal database for embodied intelligence (robots, AR glasses, industrial arms).
Documentation 
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//! Octant node implementation for i-Octree
//!
//! Leaf nodes hold a `leaf_id` referencing data in the LeafStore,
//! keeping memory bounded regardless of data volume.

use serde::{Deserialize, Serialize};

/// Compact 3D point with associated row ID (f64 for precision)
#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub struct IndexedPoint3D {
    pub x: f64,
    pub y: f64,
    pub z: f64,
    pub row_id: u64,
}

impl IndexedPoint3D {
    pub fn from_point3d(p: &crate::types::Point3D, row_id: u64) -> Self {
        Self {
            x: p.x,
            y: p.y,
            z: p.z,
            row_id,
        }
    }

    pub fn distance_squared(&self, other: &[f64; 3]) -> f64 {
        let dx = self.x - other[0];
        let dy = self.y - other[1];
        let dz = self.z - other[2];
        dx * dx + dy * dy + dz * dz
    }

    pub fn as_array(&self) -> [f64; 3] {
        [self.x, self.y, self.z]
    }
}

/// Octant node: inner node with 8 children, or leaf with disk-backed data
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum Octant {
    Inner {
        center: [f64; 3],
        extent: f64,
        children: Box<[Option<Box<Octant>>; 8]>,
        size: usize,
    },
    Leaf {
        center: [f64; 3],
        extent: f64,
        /// Leaf ID referencing data in LeafStore
        leaf_id: u64,
        /// Cached point count (kept in sync with LeafStore)
        point_count: u32,
    },
}

/// Compute which child octant a point belongs to (Morton code)
pub fn octant_code(center: &[f64; 3], point: &[f64; 3]) -> usize {
    let mut code = 0u8;
    if point[0] >= center[0] {
        code |= 1;
    }
    if point[1] >= center[1] {
        code |= 2;
    }
    if point[2] >= center[2] {
        code |= 4;
    }
    code as usize
}

/// Compute child center given parent center, extent, and octant code
pub fn child_center(parent_center: &[f64; 3], parent_extent: f64, code: usize) -> [f64; 3] {
    let half = parent_extent / 2.0;
    let mut center = *parent_center;
    if code & 1 != 0 {
        center[0] += half;
    } else {
        center[0] -= half;
    }
    if code & 2 != 0 {
        center[1] += half;
    } else {
        center[1] -= half;
    }
    if code & 4 != 0 {
        center[2] += half;
    } else {
        center[2] -= half;
    }
    center
}

impl Octant {
    pub fn new_leaf(center: [f64; 3], extent: f64, leaf_id: u64) -> Self {
        Octant::Leaf {
            center,
            extent,
            leaf_id,
            point_count: 0,
        }
    }

    pub fn new_inner(center: [f64; 3], extent: f64) -> Self {
        Octant::Inner {
            center,
            extent,
            children: Box::new([None, None, None, None, None, None, None, None]),
            size: 0,
        }
    }

    pub fn size(&self) -> usize {
        match self {
            Octant::Inner { size, .. } => *size,
            Octant::Leaf { point_count, .. } => *point_count as usize,
        }
    }

    pub fn extent(&self) -> f64 {
        match self {
            Octant::Inner { extent, .. } | Octant::Leaf { extent, .. } => *extent,
        }
    }

    pub fn center(&self) -> &[f64; 3] {
        match self {
            Octant::Inner { center, .. } | Octant::Leaf { center, .. } => center,
        }
    }

    pub fn leaf_id(&self) -> Option<u64> {
        match self {
            Octant::Leaf { leaf_id, .. } => Some(*leaf_id),
            _ => None,
        }
    }

    /// Recount total size from children
    pub fn recount_size(&mut self) {
        if let Octant::Inner { children, size, .. } = self {
            *size = 0;
            for c in children.iter().flatten() {
                *size += c.size();
            }
        }
    }

    /// Estimate memory usage of the tree structure (not including leaf data in LeafStore)
    pub fn memory_usage(&self) -> usize {
        match self {
            Octant::Leaf { .. } => std::mem::size_of::<Octant>(),
            Octant::Inner { children, .. } => {
                let mut total = std::mem::size_of::<Octant>();
                for c in children.iter().flatten() {
                    total += c.memory_usage();
                }
                total
            }
        }
    }
}

/// Check if an octant (center + extent) overlaps with a 3D box [min, max]
pub fn overlaps(center: &[f64; 3], extent: f64, min: &[f64; 3], max: &[f64; 3]) -> bool {
    center[0] + extent >= min[0]
        && center[0] - extent <= max[0]
        && center[1] + extent >= min[1]
        && center[1] - extent <= max[1]
        && center[2] + extent >= min[2]
        && center[2] - extent <= max[2]
}

/// Minimum squared distance from a point to an octant's boundary (0 if inside)
pub fn min_dist_sq_to_octant(center: &[f64; 3], extent: f64, point: &[f64; 3]) -> f64 {
    let mut dist_sq = 0.0f64;
    for i in 0..3 {
        let lo = center[i] - extent;
        let hi = center[i] + extent;
        if point[i] < lo {
            dist_sq += (point[i] - lo).powi(2);
        } else if point[i] > hi {
            dist_sq += (point[i] - hi).powi(2);
        }
    }
    dist_sq
}