feat(nav): 17.1/17.3 - ludic.nav over Recast & Detour v1.6.0 (zlib), built here from the pinned tag on the Mac and the PC (the DLL imports KERNEL32 alone): a navmesh per kind of walker from triangles with an area byte each and cylinders nothing stands in, saved and loaded as bytes; the nearest point, a path as corners (partial when the end cannot be reached), whether a straight line stays walkable, a cost per kind of ground. Tests on a hand-built meadow: round a post, over a ford, stopped at a bank, a saved mesh answering alike - Mac and PC

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

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

@@ -0,0 +1,108 @@
+// nav_build.inl - a navmesh from triangles: Recast's solo pipeline (rasterize, filter, erode,
+// regions, contours, polygons, detail) and one Detour tile. c[] is the configuration:
+// cell size, cell height, agent height, agent radius, max climb, max slope (degrees).
+
+// 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) {
+  for (int i = 0; i < nc; ++i) {
+    float pos[3] = {cyl[i * 5], cyl[i * 5 + 1], cyl[i * 5 + 2]};
+    rcMarkCylinderArea(&ctx, pos, cyl[i * 5 + 3], cyl[i * 5 + 4], RC_NULL_AREA, chf);
+  }
+}
+
+// v: nv points (x, y, z); t: nt triangles; area: one per triangle, 0 not walkable, 1..62 a kind of
+// ground (its cost is the filter's); the slope clears what is too steep whatever its area
+NAV_SHIM void *nav_build(const float *v, int nv, const int *t, int nt, const unsigned char *area,
+                         const float *cyl, int nc, const float *c) {
+  rcContext ctx(false);
+  rcConfig cfg;
+  memset(&cfg, 0, sizeof(cfg));
+  cfg.cs = c[0];
+  cfg.ch = c[1];
+  cfg.walkableSlopeAngle = c[5];
+  cfg.walkableHeight = (int)ceilf(c[2] / cfg.ch);
+  cfg.walkableClimb = (int)floorf(c[4] / cfg.ch);
+  cfg.walkableRadius = (int)ceilf(c[3] / cfg.cs);
+  cfg.maxEdgeLen = (int)(12.0f / cfg.cs);
+  cfg.maxSimplificationError = 1.3f;
+  cfg.minRegionArea = 8 * 8;
+  cfg.mergeRegionArea = 20 * 20;
+  cfg.maxVertsPerPoly = 6;
+  cfg.detailSampleDist = cfg.cs * 6.0f;
+  cfg.detailSampleMaxError = cfg.ch;
+  rcCalcBounds(v, nv, cfg.bmin, cfg.bmax);
+  rcCalcGridSize(cfg.bmin, cfg.bmax, cfg.cs, &cfg.width, &cfg.height);
+
+  std::vector<unsigned char> areas(area, area + nt);
+  rcClearUnwalkableTriangles(&ctx, cfg.walkableSlopeAngle, v, nv, t, nt, areas.data());
+  rcHeightfield *hf = rcAllocHeightfield();
+  rcCompactHeightfield *chf = rcAllocCompactHeightfield();
+  rcContourSet *cs = rcAllocContourSet();
+  rcPolyMesh *pm = rcAllocPolyMesh();
+  rcPolyMeshDetail *dm = rcAllocPolyMeshDetail();
+  bool ok = hf && chf && cs && pm && dm &&
+            rcCreateHeightfield(&ctx, *hf, cfg.width, cfg.height, cfg.bmin, cfg.bmax, cfg.cs, cfg.ch) &&
+            rcRasterizeTriangles(&ctx, v, nv, t, areas.data(), nt, *hf, cfg.walkableClimb);
+  if (ok) {
+    rcFilterLowHangingWalkableObstacles(&ctx, cfg.walkableClimb, *hf);
+    rcFilterLedgeSpans(&ctx, cfg.walkableHeight, cfg.walkableClimb, *hf);
+    rcFilterWalkableLowHeightSpans(&ctx, cfg.walkableHeight, *hf);
+    ok = rcBuildCompactHeightfield(&ctx, cfg.walkableHeight, cfg.walkableClimb, *hf, *chf);
+  }
+  if (ok) {
+    nav_mark_cylinders(ctx, *chf, cyl, nc);
+    ok = rcErodeWalkableArea(&ctx, cfg.walkableRadius, *chf) && rcBuildDistanceField(&ctx, *chf) &&
+         rcBuildRegions(&ctx, *chf, 0, cfg.minRegionArea, cfg.mergeRegionArea) &&
+         rcBuildContours(&ctx, *chf, cfg.maxSimplificationError, cfg.maxEdgeLen, *cs) &&
+         rcBuildPolyMesh(&ctx, *cs, cfg.maxVertsPerPoly, *pm) &&
+         rcBuildPolyMeshDetail(&ctx, *pm, *chf, cfg.detailSampleDist, cfg.detailSampleMaxError, *dm);
+  }
+  unsigned char *data = nullptr;
+  int size = 0;
+  if (ok) {
+    for (int i = 0; i < pm->npolys; ++i) pm->flags[i] = pm->areas[i] ? 1 : 0;
+    dtNavMeshCreateParams p;
+    memset(&p, 0, sizeof(p));
+    p.verts = pm->verts; p.vertCount = pm->nverts; p.polys = pm->polys; p.polyAreas = pm->areas;
+    p.polyFlags = pm->flags; p.polyCount = pm->npolys; p.nvp = pm->nvp;
+    p.detailMeshes = dm->meshes; p.detailVerts = dm->verts; p.detailVertsCount = dm->nverts;
+    p.detailTris = dm->tris; p.detailTriCount = dm->ntris;
+    p.walkableHeight = c[2]; p.walkableRadius = c[3]; p.walkableClimb = c[4];
+    rcVcopy(p.bmin, pm->bmin); rcVcopy(p.bmax, pm->bmax);
+    p.cs = cfg.cs; p.ch = cfg.ch; p.buildBvTree = true;
+    ok = dtCreateNavMeshData(&p, &data, &size);
+  }
+  rcFreeHeightField(hf); rcFreeCompactHeightfield(chf); rcFreeContourSet(cs); rcFreePolyMesh(pm); rcFreePolyMeshDetail(dm);
+  if (!ok) return nullptr;
+  return nav_from(data, size);
+}
+
+// the tile's bytes, to write to a file: first the size (buf null), then the copy
+NAV_SHIM int nav_save(void *h, unsigned char *buf, int cap) {
+  Nav *n = static_cast<Nav *>(h);
+  if (!buf) return n->size;
+  if (cap < n->size) return -1;
+  memcpy(buf, n->data, n->size);
+  return n->size;
+}
+
+// a navmesh from bytes nav_save wrote
+NAV_SHIM void *nav_load(const unsigned char *buf, int size) {
+  unsigned char *data = static_cast<unsigned char *>(dtAlloc(size, DT_ALLOC_PERM));
+  if (!data) return nullptr;
+  memcpy(data, buf, size);
+  return nav_from(data, size);
+}
+
+NAV_SHIM void nav_free(void *h) {
+  Nav *n = static_cast<Nav *>(h);
+  if (!n) return;
+  dtFreeNavMeshQuery(n->query);
+  dtFreeNavMesh(n->mesh);
+  delete n;
+}
+
+NAV_SHIM int nav_polys(void *h) {
+  const dtMeshTile *t = static_cast<const dtNavMesh *>(static_cast<Nav *>(h)->mesh)->getTile(0);
+  return t && t->header ? t->header->polyCount : 0;
+}