fix(nav): nothing allocated per build - the configuration and the empty lists live in NavState, because Ludic never gives an allocation back and a map is thousands of tile builds; nav_drop lets one kind's mesh go; the detail mesh's spacing is a NavConfig setting held to Recast's own floor of 0.9 m (0 took a 40 m test meadow to 3.5 GB)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.nav/build.ludic

@@ -5,25 +5,28 @@ function nv_ground_ok(g: NavGround) -> bool {
   if g.nc > 0 and (g.cyl == null or len(g.cyl) < g.nc * 5) { return false }
   return g.nf == 0 or (g.foot != null and len(g.foot) >= g.nf)
 }
-function nv_cfg(c: NavConfig) -> []float {
-  let cfg = floats(6)
+# the configuration in the state's own buffer: a map is thousands of tile builds, and nothing
+# allocated per build is ever given back
+function nv_cfg(nav_st: mut NavState, c: NavConfig) -> []float {
+  let cfg = nav_st.nv_cfg
   cfg[0] = c.cell
   cfg[1] = c.cell_h
   cfg[2] = c.height
   cfg[3] = c.radius
   cfg[4] = c.climb
   cfg[5] = c.slope
+  cfg[6] = Math.max(c.detail, 0.9)
   return cfg
 }
-function nv_or_none(xs: []float) -> []float {
-  if xs == null { return floats(1) }
+function nv_or_none(nav_st: NavState, xs: []float, n: int) -> []float {
+  if xs == null or n == 0 { return nav_st.nv_empty }
   return xs
 }
 
 # one mesh over the whole of g
 export function nav_build(nav_st: mut NavState, kind: int, g: NavGround, c: NavConfig) -> bool {
   if not nv_ground_ok(g) { return false }
-  return nv_set(nav_st, kind, nvc_build(g.v, g.nv, g.t, g.nt, g.area, nv_or_none(g.cyl), g.nc, nv_or_none(g.foot), g.nf, nv_cfg(c)))
+  return nv_set(nav_st, kind, nvc_build(g.v, g.nv, g.t, g.nt, g.area, nv_or_none(nav_st, g.cyl, g.nc), g.nc, nv_or_none(nav_st, g.foot, g.nf), g.nf, nv_cfg(nav_st, c)))
 }
 
 # an empty mesh of square tiles `tile` metres across from (ox, oz), for a map built a tile at a time
@@ -31,10 +34,10 @@ export function nav_tiled(nav_st: mut NavState, kind: int, ox: float, oz: float,
   return nv_set(nav_st, kind, nvc_tiled(ox, oz, tile, max_tiles, max_polys))
 }
 # tile (tx, tz) from ground g covering it and a few metres round it: its polygons, 0 none, -1 failed
-export function nav_tile_build(nav_st: NavState, kind: int, tx: int, tz: int, g: NavGround, c: NavConfig) -> int {
+export function nav_tile_build(nav_st: mut NavState, kind: int, tx: int, tz: int, g: NavGround, c: NavConfig) -> int {
   let h = nv_mesh(nav_st, kind)
   if h == null or not nv_ground_ok(g) { return -1 }
-  return nvc_tile_build(h, tx, tz, g.v, g.nv, g.t, g.nt, g.area, nv_or_none(g.cyl), g.nc, nv_or_none(g.foot), g.nf, nv_cfg(c))
+  return nvc_tile_build(h, tx, tz, g.v, g.nv, g.t, g.nt, g.area, nv_or_none(nav_st, g.cyl, g.nc), g.nc, nv_or_none(nav_st, g.foot, g.nf), g.nf, nv_cfg(nav_st, c))
 }
 
 # the polygons a kind's mesh has (0: none)
@@ -44,7 +47,8 @@ export function nav_polygons(nav_st: NavState, kind: int) -> int {
   return nvc_polys(h)
 }
 
-# a kind's mesh written to a file, and read back
+# a kind's mesh written to a file, and read back. Reading holds the file's bytes for good (a slice
+# is never given back), so a mesh is loaded once per map, never per frame
 export function nav_save_file(nav_st: NavState, kind: int, path: string) -> bool {
   let h = nv_mesh(nav_st, kind)
   if h == null { return false }

packages/ludic.nav/native/shim/nav_build.inl

@@ -1,6 +1,7 @@
 // nav_build.inl - Recast's pipeline, shared by a whole mesh and a tile: rasterize the triangles,
 // filter, mark what nothing stands in, erode, regions, contours, polygons, detail, Detour's data.
-// c[] is the configuration: cell size, cell height, agent height, radius, max climb, max slope.
+// c[] is the configuration: cell size, cell height, agent height, radius, max climb, max slope, and
+// the detail mesh's sample spacing (at least 0.9 m, Recast's own limit; 0 grew without bound)
 
 // cylinders (x, y, z, r, h each) no agent may stand in: trunks, posts, tents
 static void nav_mark_cylinders(rcContext &ctx, rcCompactHeightfield &chf, const float *cyl, int nc) {
@@ -37,7 +38,7 @@ static void nav_config(rcConfig &cfg, const float *c) {
   cfg.minRegionArea = 8 * 8;
   cfg.mergeRegionArea = 20 * 20;
   cfg.maxVertsPerPoly = 6;
-  cfg.detailSampleDist = cfg.cs * 6.0f;
+  cfg.detailSampleDist = c[6] > 0.9f ? c[6] : 0.9f;
   cfg.detailSampleMaxError = cfg.ch;
 }
 

packages/ludic.nav/state.ludic

@@ -16,6 +16,7 @@ export property NavConfig {
   radius: float = 0.35
   climb: float = 0.55
   slope: float = 45.0
+  detail: float = 1.5   # the detail mesh's samples, metres apart (at least 0.9: 0 took one small test to 3.5 GB)
 }
 
 # what a mesh is built from: v holds nv points (x, y, z) and t nt triangles (three indices each);
@@ -38,6 +39,8 @@ export state NavState {
   nv_out: []float = floats(NAV_CORNERS * 3)
   nv_count: int = 0
   nv_near: []float = floats(3)
+  nv_cfg: []float = floats(7)      # the configuration handed to the shim, filled in place per build
+  nv_empty: []float = floats(1)    # what the shim is handed for no cylinders or no footprints
 }
 function nv_none() -> []pointer {
   let m = new []pointer
@@ -55,6 +58,9 @@ function nv_set(nav_st: mut NavState, kind: int, h: pointer) -> bool {
   return h != null
 }
 
+# one kind's mesh let go (a bake writes each kind and drops it before the next)
+export function nav_drop(nav_st: mut NavState, kind: int) -> void { nv_set(nav_st, kind, null) }
+
 # every mesh let go: a new map, or the world closed
 export function nav_reset(nav_st: mut NavState) -> void {
   for k in 0 .. NAV_KINDS { nv_set(nav_st, k, null) }