tawasuyu/brahman

Fase F: sexto stub de pineal cerrado (6/6).

mesh resultó ser un módulo de viz de grafos, no un triangle-mesh.
Núcleo implementado:
- buffers — NodeBuffer (stride 3: x,y,radius) + EdgeBuffer (stride 2),
  Vec planos contiguos, raw() para subir a GPU.
- spatial_hash — uniform grid; rebuild + query (nodo bajo un punto,
  revisa celda + 8 vecinas).
- force — layout force-directed Fruchterman-Reingold naïve O(n²):
  repulsión todo-par + atracción por arista + cooling. Jitter
  determinista para nodos coincidentes.
- tree — layout de árbol por ancho de subárbol (post-order, padres
  centrados sobre hijos), soporta bosque, ciclos sin colgar.
- camera — pan/zoom con zoom anclado al cursor (anchor-preserving).

13 tests verdes. cargo check --workspace verde.

Pendiente (follow-up): hierarchical (Sugiyama) + Barnes-Hut para
escalar el force-directed a grafos masivos.

Pineal: 6/6 stubs cerrados.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

diff --git a/crates/modules/pineal/mesh/src/buffers.rs b/crates/modules/pineal/mesh/src/buffers.rs
new file mode 100644
index 0000000..251a652
--- /dev/null
+++ b/crates/modules/pineal/mesh/src/buffers.rs
@@ -0,0 +1,111 @@
+//! Buffers planos de nodos y aristas — `Vec` contiguos con stride fijo.
+
+/// Nodos: stride 3 = `[x, y, radius]` por nodo.
+#[derive(Debug, Clone, Default)]
+pub struct NodeBuffer {
+    data: Vec<f32>,
+}
+
+impl NodeBuffer {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn with_capacity(n: usize) -> Self {
+        Self { data: Vec::with_capacity(n * 3) }
+    }
+
+    /// Agrega un nodo y devuelve su índice.
+    pub fn push(&mut self, x: f32, y: f32, radius: f32) -> usize {
+        let idx = self.len();
+        self.data.extend_from_slice(&[x, y, radius]);
+        idx
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.len() / 3
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.data.is_empty()
+    }
+
+    pub fn pos(&self, i: usize) -> (f32, f32) {
+        (self.data[i * 3], self.data[i * 3 + 1])
+    }
+
+    pub fn radius(&self, i: usize) -> f32 {
+        self.data[i * 3 + 2]
+    }
+
+    pub fn set_pos(&mut self, i: usize, x: f32, y: f32) {
+        self.data[i * 3] = x;
+        self.data[i * 3 + 1] = y;
+    }
+
+    /// Acceso crudo al `Vec<f32>` interleaved — para subir como buffer GPU.
+    pub fn raw(&self) -> &[f32] {
+        &self.data
+    }
+}
+
+/// Aristas: stride 2 = `[from, to]` (índices de nodo).
+#[derive(Debug, Clone, Default)]
+pub struct EdgeBuffer {
+    data: Vec<u32>,
+}
+
+impl EdgeBuffer {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn push(&mut self, from: usize, to: usize) {
+        self.data.push(from as u32);
+        self.data.push(to as u32);
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.len() / 2
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.data.is_empty()
+    }
+
+    pub fn edge(&self, i: usize) -> (usize, usize) {
+        (self.data[i * 2] as usize, self.data[i * 2 + 1] as usize)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (usize, usize)> + '_ {
+        (0..self.len()).map(move |i| self.edge(i))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn node_buffer_push_and_access() {
+        let mut nb = NodeBuffer::new();
+        let a = nb.push(1.0, 2.0, 5.0);
+        let b = nb.push(3.0, 4.0, 6.0);
+        assert_eq!((a, b), (0, 1));
+        assert_eq!(nb.len(), 2);
+        assert_eq!(nb.pos(1), (3.0, 4.0));
+        assert_eq!(nb.radius(0), 5.0);
+        nb.set_pos(0, 9.0, 9.0);
+        assert_eq!(nb.pos(0), (9.0, 9.0));
+    }
+
+    #[test]
+    fn edge_buffer_roundtrip() {
+        let mut eb = EdgeBuffer::new();
+        eb.push(0, 1);
+        eb.push(1, 2);
+        assert_eq!(eb.len(), 2);
+        assert_eq!(eb.edge(1), (1, 2));
+        assert_eq!(eb.iter().collect::<Vec<_>>(), vec![(0, 1), (1, 2)]);
+    }
+}
diff --git a/crates/modules/pineal/mesh/src/camera.rs b/crates/modules/pineal/mesh/src/camera.rs
new file mode 100644
index 0000000..0f890f6
--- /dev/null
+++ b/crates/modules/pineal/mesh/src/camera.rs
@@ -0,0 +1,72 @@
+//! Cámara 2D: pan + zoom con zoom anclado a un punto de pantalla.
+
+/// Transformación world↔screen. `screen = (world - pan) * zoom`.
+#[derive(Debug, Clone, Copy)]
+pub struct Camera {
+    pub pan: (f32, f32),
+    pub zoom: f32,
+}
+
+impl Default for Camera {
+    fn default() -> Self {
+        Self { pan: (0.0, 0.0), zoom: 1.0 }
+    }
+}
+
+impl Camera {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn world_to_screen(&self, w: (f32, f32)) -> (f32, f32) {
+        ((w.0 - self.pan.0) * self.zoom, (w.1 - self.pan.1) * self.zoom)
+    }
+
+    pub fn screen_to_world(&self, s: (f32, f32)) -> (f32, f32) {
+        (s.0 / self.zoom + self.pan.0, s.1 / self.zoom + self.pan.1)
+    }
+
+    /// Desplaza la cámara `delta` pixels de pantalla.
+    pub fn pan_by(&mut self, dx: f32, dy: f32) {
+        self.pan.0 -= dx / self.zoom;
+        self.pan.1 -= dy / self.zoom;
+    }
+
+    /// Zoom multiplicando por `factor`, manteniendo fijo el punto de
+    /// pantalla `anchor` (el world-point bajo el cursor no se mueve).
+    pub fn zoom_at(&mut self, anchor: (f32, f32), factor: f32) {
+        let before = self.screen_to_world(anchor);
+        self.zoom = (self.zoom * factor).clamp(0.01, 1000.0);
+        let after = self.screen_to_world(anchor);
+        self.pan.0 += before.0 - after.0;
+        self.pan.1 += before.1 - after.1;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn close(a: (f32, f32), b: (f32, f32)) -> bool {
+        (a.0 - b.0).abs() < 1e-3 && (a.1 - b.1).abs() < 1e-3
+    }
+
+    #[test]
+    fn world_screen_roundtrip() {
+        let mut cam = Camera::new();
+        cam.pan = (10.0, 20.0);
+        cam.zoom = 2.0;
+        let w = (33.0, 44.0);
+        assert!(close(cam.screen_to_world(cam.world_to_screen(w)), w));
+    }
+
+    #[test]
+    fn zoom_at_keeps_anchor_world_point_fixed() {
+        let mut cam = Camera::new();
+        let anchor = (100.0, 80.0);
+        let before = cam.screen_to_world(anchor);
+        cam.zoom_at(anchor, 2.5);
+        let after = cam.screen_to_world(anchor);
+        assert!(close(before, after), "el punto bajo el cursor no se mueve");
+    }
+}
diff --git a/crates/modules/pineal/mesh/src/force.rs b/crates/modules/pineal/mesh/src/force.rs
new file mode 100644
index 0000000..918045d
--- /dev/null
+++ b/crates/modules/pineal/mesh/src/force.rs
@@ -0,0 +1,154 @@
+//! Layout force-directed (Fruchterman-Reingold).
+//!
+//! Repulsión entre todo par de nodos + atracción a lo largo de las
+//! aristas, integrado con cooling. Implementación naïve O(n²); Barnes-Hut
+//! es la optimización de escala (millones de nodos) — pendiente.
+
+use crate::buffers::{EdgeBuffer, NodeBuffer};
+
+/// Parámetros de la simulación.
+#[derive(Debug, Clone, Copy)]
+pub struct ForceParams {
+    /// Distancia ideal entre nodos conectados.
+    pub k: f32,
+    /// Desplazamiento máximo inicial por paso (se enfría).
+    pub temperature: f32,
+    /// Factor de enfriamiento aplicado cada paso (`0 < cooling < 1`).
+    pub cooling: f32,
+}
+
+impl Default for ForceParams {
+    fn default() -> Self {
+        Self { k: 50.0, temperature: 50.0, cooling: 0.95 }
+    }
+}
+
+/// Estado de una simulación force-directed.
+pub struct ForceLayout {
+    params: ForceParams,
+    temp: f32,
+}
+
+impl ForceLayout {
+    pub fn new(params: ForceParams) -> Self {
+        let temp = params.temperature;
+        Self { params, temp }
+    }
+
+    /// Temperatura actual (baja con cada paso — útil para detectar fin).
+    pub fn temperature(&self) -> f32 {
+        self.temp
+    }
+
+    /// Un paso de simulación. Muta las posiciones de `nodes`. Devuelve el
+    /// desplazamiento total aplicado (converge hacia 0).
+    pub fn step(&mut self, nodes: &mut NodeBuffer, edges: &EdgeBuffer) -> f32 {
+        let n = nodes.len();
+        if n == 0 {
+            return 0.0;
+        }
+        let k = self.params.k.max(1e-3);
+        let mut disp = vec![(0.0f32, 0.0f32); n];
+
+        // Repulsión: todo par. f_r = k² / d.
+        for i in 0..n {
+            let (xi, yi) = nodes.pos(i);
+            for j in (i + 1)..n {
+                let (xj, yj) = nodes.pos(j);
+                let mut dx = xi - xj;
+                let mut dy = yi - yj;
+                let mut dist = (dx * dx + dy * dy).sqrt();
+                if dist < 1e-3 {
+                    // Jitter determinista para despegar nodos coincidentes.
+                    dx = ((i as f32) - (j as f32)) * 0.01 + 0.01;
+                    dy = 0.01;
+                    dist = (dx * dx + dy * dy).sqrt();
+                }
+                let f = k * k / dist;
+                let (ux, uy) = (dx / dist, dy / dist);
+                disp[i].0 += ux * f;
+                disp[i].1 += uy * f;
+                disp[j].0 -= ux * f;
+                disp[j].1 -= uy * f;
+            }
+        }
+
+        // Atracción: a lo largo de cada arista. f_a = d² / k.
+        for (u, v) in edges.iter() {
+            if u >= n || v >= n || u == v {
+                continue;
+            }
+            let (xu, yu) = nodes.pos(u);
+            let (xv, yv) = nodes.pos(v);
+            let dx = xu - xv;
+            let dy = yu - yv;
+            let dist = (dx * dx + dy * dy).sqrt().max(1e-3);
+            let f = dist * dist / k;
+            let (ux, uy) = (dx / dist, dy / dist);
+            disp[u].0 -= ux * f;
+            disp[u].1 -= uy * f;
+            disp[v].0 += ux * f;
+            disp[v].1 += uy * f;
+        }
+
+        // Integración con cap de temperatura.
+        let mut total = 0.0f32;
+        for i in 0..n {
+            let (dx, dy) = disp[i];
+            let len = (dx * dx + dy * dy).sqrt();
+            if len < 1e-6 {
+                continue;
+            }
+            let capped = len.min(self.temp);
+            let (mx, my) = (dx / len * capped, dy / len * capped);
+            let (x, y) = nodes.pos(i);
+            nodes.set_pos(i, x + mx, y + my);
+            total += capped;
+        }
+        self.temp *= self.params.cooling;
+        total
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn two_connected_nodes_settle_near_k() {
+        let mut nb = NodeBuffer::new();
+        nb.push(0.0, 0.0, 5.0);
+        nb.push(500.0, 0.0, 5.0); // arrancan muy lejos
+        let mut eb = EdgeBuffer::new();
+        eb.push(0, 1);
+        let mut fl = ForceLayout::new(ForceParams::default());
+        for _ in 0..400 {
+            fl.step(&mut nb, &eb);
+        }
+        let (x0, y0) = nb.pos(0);
+        let (x1, y1) = nb.pos(1);
+        let dist = ((x1 - x0).powi(2) + (y1 - y0).powi(2)).sqrt();
+        // No deberían quedar ni pegados ni a 500 de distancia.
+        assert!(dist > 5.0 && dist < 300.0, "dist tras converger = {dist}");
+    }
+
+    #[test]
+    fn coincident_nodes_do_not_nan() {
+        let mut nb = NodeBuffer::new();
+        nb.push(10.0, 10.0, 5.0);
+        nb.push(10.0, 10.0, 5.0);
+        let eb = EdgeBuffer::new();
+        let mut fl = ForceLayout::new(ForceParams::default());
+        fl.step(&mut nb, &eb);
+        let (x, y) = nb.pos(0);
+        assert!(x.is_finite() && y.is_finite());
+    }
+
+    #[test]
+    fn empty_graph_is_noop() {
+        let mut nb = NodeBuffer::new();
+        let eb = EdgeBuffer::new();
+        let mut fl = ForceLayout::new(ForceParams::default());
+        assert_eq!(fl.step(&mut nb, &eb), 0.0);
+    }
+}
diff --git a/crates/modules/pineal/mesh/src/lib.rs b/crates/modules/pineal/mesh/src/lib.rs
index d243c0e..633f78e 100644
--- a/crates/modules/pineal/mesh/src/lib.rs
+++ b/crates/modules/pineal/mesh/src/lib.rs
@@ -1,28 +1,25 @@
 //! `pineal-mesh` — visualización de grafos.
 //!
-//! Módulos:
-//! - **`node_buffer`** / **`edge_buffer`** — `Vec<f32>` planos con
-//!   stride fijo (3 floats por nodo: `[x, y, radius]`).
-//! - **`spatial_hash`** — uniform grid para hit-test de nodos
-//!   móviles (sección 5.1).
-//! - **`force_directed`** — layout con Barnes-Hut delegado a
-//!   `pineal_core::barnes_hut` (cuando se implemente).
-//! - **`hierarchical`** — Sugiyama-lite, delegado a
-//!   `pineal_core::sugiyama`.
-//! - **`tree`** — subtree-width layout, delegado a
-//!   `pineal_core::tree_layout`.
-//! - **`camera`** — pan/zoom con anchor-preserving zoom de la
-//!   sección 5.3.
-//! - **`element`** — `Element` GPUI.
+//! - [`buffers`] — `NodeBuffer` / `EdgeBuffer`: `Vec` planos con stride
+//!   fijo (3 floats por nodo `[x,y,radius]`, 2 por arista).
+//! - [`spatial_hash`] — uniform grid para hit-test de nodos móviles.
+//! - [`force`] — layout force-directed (Fruchterman-Reingold naïve).
+//! - [`tree`] — layout de árbol por ancho de subárbol.
+//! - [`camera`] — pan/zoom con zoom anclado al cursor.
+//!
+//! Pendiente: `hierarchical` (Sugiyama, layered graph drawing) y la
+//! optimización Barnes-Hut del force-directed para grafos masivos.
 
 #![forbid(unsafe_code)]
-#![allow(dead_code)]
 
-pub mod node_buffer {}
-pub mod edge_buffer {}
-pub mod spatial_hash {}
-pub mod force_directed {}
-pub mod hierarchical {}
-pub mod tree {}
-pub mod camera {}
-pub mod element {}
+pub mod buffers;
+pub mod camera;
+pub mod force;
+pub mod spatial_hash;
+pub mod tree;
+
+pub use buffers::{EdgeBuffer, NodeBuffer};
+pub use camera::Camera;
+pub use force::{ForceLayout, ForceParams};
+pub use spatial_hash::SpatialHash;
+pub use tree::tree_layout;
diff --git a/crates/modules/pineal/mesh/src/spatial_hash.rs b/crates/modules/pineal/mesh/src/spatial_hash.rs
new file mode 100644
index 0000000..aade27e
--- /dev/null
+++ b/crates/modules/pineal/mesh/src/spatial_hash.rs
@@ -0,0 +1,80 @@
+//! Uniform grid para hit-test de nodos móviles.
+
+use crate::buffers::NodeBuffer;
+use std::collections::HashMap;
+
+/// Grid de celdas cuadradas. `rebuild` lo repuebla; `query` busca el
+/// nodo cuyo radio cubre un punto.
+pub struct SpatialHash {
+    cell: f32,
+    map: HashMap<(i32, i32), Vec<usize>>,
+}
+
+impl SpatialHash {
+    /// `cell_size` conviene ~2× el radio típico de nodo.
+    pub fn new(cell_size: f32) -> Self {
+        Self { cell: cell_size.max(1.0), map: HashMap::new() }
+    }
+
+    fn cell_of(&self, x: f32, y: f32) -> (i32, i32) {
+        ((x / self.cell).floor() as i32, (y / self.cell).floor() as i32)
+    }
+
+    /// Repuebla el grid con las posiciones actuales de los nodos.
+    pub fn rebuild(&mut self, nodes: &NodeBuffer) {
+        self.map.clear();
+        for i in 0..nodes.len() {
+            let (x, y) = nodes.pos(i);
+            self.map.entry(self.cell_of(x, y)).or_default().push(i);
+        }
+    }
+
+    /// Devuelve el nodo más cercano a `(x,y)` cuyo radio lo cubre, o
+    /// `None`. Revisa la celda del punto y sus 8 vecinas.
+    pub fn query(&self, nodes: &NodeBuffer, x: f32, y: f32) -> Option<usize> {
+        let (cx, cy) = self.cell_of(x, y);
+        let mut best: Option<(usize, f32)> = None;
+        for dy in -1..=1 {
+            for dx in -1..=1 {
+                if let Some(bucket) = self.map.get(&(cx + dx, cy + dy)) {
+                    for &i in bucket {
+                        let (nx, ny) = nodes.pos(i);
+                        let r = nodes.radius(i);
+                        let d2 = (nx - x).powi(2) + (ny - y).powi(2);
+                        if d2 <= r * r && best.map(|(_, bd)| d2 < bd).unwrap_or(true) {
+                            best = Some((i, d2));
+                        }
+                    }
+                }
+            }
+        }
+        best.map(|(i, _)| i)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn query_hits_node_under_point() {
+        let mut nb = NodeBuffer::new();
+        nb.push(10.0, 10.0, 5.0);
+        nb.push(100.0, 100.0, 8.0);
+        let mut sh = SpatialHash::new(20.0);
+        sh.rebuild(&nb);
+        assert_eq!(sh.query(&nb, 12.0, 11.0), Some(0));
+        assert_eq!(sh.query(&nb, 103.0, 98.0), Some(1));
+    }
+
+    #[test]
+    fn query_misses_empty_space() {
+        let mut nb = NodeBuffer::new();
+        nb.push(10.0, 10.0, 5.0);
+        let mut sh = SpatialHash::new(20.0);
+        sh.rebuild(&nb);
+        assert_eq!(sh.query(&nb, 500.0, 500.0), None);
+        // fuera del radio pero misma celda
+        assert_eq!(sh.query(&nb, 18.0, 18.0), None);
+    }
+}
diff --git a/crates/modules/pineal/mesh/src/tree.rs b/crates/modules/pineal/mesh/src/tree.rs
new file mode 100644
index 0000000..4241b29
--- /dev/null
+++ b/crates/modules/pineal/mesh/src/tree.rs
@@ -0,0 +1,105 @@
+//! Layout de árbol por ancho de subárbol.
+//!
+//! Post-order: las hojas se ubican en columnas consecutivas; cada nodo
+//! interno se centra sobre sus hijos. `y` es la profundidad. Soporta
+//! bosque (múltiples raíces). Ciclos en los punteros `parent` se ignoran
+//! con gracia (esos nodos quedan en el origen).
+
+/// Calcula `(x, y)` por nodo. `parent[i] = None` marca una raíz.
+pub fn tree_layout(parent: &[Option<usize>], x_gap: f32, y_gap: f32) -> Vec<(f32, f32)> {
+    let n = parent.len();
+    let mut pos = vec![(0.0f32, 0.0f32); n];
+    if n == 0 {
+        return pos;
+    }
+
+    let mut children: Vec<Vec<usize>> = vec![Vec::new(); n];
+    let mut roots: Vec<usize> = Vec::new();
+    for i in 0..n {
+        match parent[i] {
+            Some(p) if p < n && p != i => children[p].push(i),
+            _ => roots.push(i),
+        }
+    }
+
+    // Profundidad por BFS desde las raíces.
+    let mut depth = vec![0usize; n];
+    let mut visited = vec![false; n];
+    let mut queue: Vec<usize> = roots.clone();
+    for &r in &roots {
+        visited[r] = true;
+    }
+    let mut head = 0;
+    while head < queue.len() {
+        let u = queue[head];
+        head += 1;
+        for &c in &children[u] {
+            if !visited[c] {
+                visited[c] = true;
+                depth[c] = depth[u] + 1;
+                queue.push(c);
+            }
+        }
+    }
+
+    // Asignación de `x` por post-order iterativo, raíz por raíz.
+    let mut next_leaf = 0.0f32;
+    for &root in &roots {
+        let mut stack: Vec<(usize, usize)> = vec![(root, 0)];
+        while let Some(&mut (u, ref mut ci)) = stack.last_mut() {
+            if *ci < children[u].len() {
+                let c = children[u][*ci];
+                *ci += 1;
+                stack.push((c, 0));
+            } else {
+                if children[u].is_empty() {
+                    pos[u].0 = next_leaf;
+                    next_leaf += x_gap;
+                } else {
+                    let sum: f32 = children[u].iter().map(|&c| pos[c].0).sum();
+                    pos[u].0 = sum / children[u].len() as f32;
+                }
+                pos[u].1 = depth[u] as f32 * y_gap;
+                stack.pop();
+            }
+        }
+    }
+    pos
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn single_node_at_origin() {
+        let pos = tree_layout(&[None], 10.0, 20.0);
+        assert_eq!(pos, vec![(0.0, 0.0)]);
+    }
+
+    #[test]
+    fn parent_centered_over_two_children() {
+        // 0 raíz; 1 y 2 hijos.
+        let pos = tree_layout(&[None, Some(0), Some(0)], 10.0, 20.0);
+        assert_eq!(pos[1], (0.0, 20.0));
+        assert_eq!(pos[2], (10.0, 20.0));
+        // padre centrado en x = (0+10)/2 = 5, depth 0.
+        assert_eq!(pos[0], (5.0, 0.0));
+    }
+
+    #[test]
+    fn depth_increases_down_the_tree() {
+        // cadena 0 → 1 → 2
+        let pos = tree_layout(&[None, Some(0), Some(1)], 10.0, 20.0);
+        assert_eq!(pos[0].1, 0.0);
+        assert_eq!(pos[1].1, 20.0);
+        assert_eq!(pos[2].1, 40.0);
+    }
+
+    #[test]
+    fn cycle_in_parents_does_not_hang() {
+        // 0 ↔ 1 sin raíz: no debe colgar.
+        let pos = tree_layout(&[Some(1), Some(0)], 10.0, 20.0);
+        assert_eq!(pos.len(), 2);
+    }
+}