wgt01: real .mdl/.wok export via Neverblender

Neverblender is installed + enabled in this machine's Blender 4.0.2 config and
confirmed working headless via the flake. Add generator/export_mdl.py:
assembles each tile as a Neverblender-native model (AuroraBase dummy/tile,
trimesh, single aabb walkmesh) in its own scene and calls scene.nvb_mdlexport
to emit real ASCII <resref>.mdl + <resref>.wok for all 40 tiles.

Walkmesh surfacemats via create_wok_materials() slot order (walkable Stone=4,
Nonwalk=7) -> verified correct per tile (CP1 all 4, CN1 all 7, BR_1/CE_S mixed).

flake.nix: add `export` app (nix run .#export -- <blend> <outdir> [CODE...]).
AGENTS.md: record the Neverblender node/surfacemat facts and the kit's tools;
note the slot-index (not material-name) surfacemat gotcha.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -273,17 +273,31 @@ tracks Blender 3.x–4.x, **not** nixpkgs' Blender 5.x. Do not "upgrade" it.
 
 ### 6.1 Tools (all on `PATH` in the dev shell)
 - **NeverBlender** — Blender addon that exports NWN `.mdl` + `.wok` and defines
-  node types (trimesh, **AABB walkmesh**, dummy, light). Install a NeverBlender
+  node types (trimesh, **AABB walkmesh**, dummy, light). It is **not** bundled in
-  release compatible with **Blender 4.0.x** into this Blender
+  the stock binary, but is **installed and enabled in this machine's Blender 4.0.2
-  (`Edit ▸ Preferences ▸ Add-ons ▸ Install`). It is **not** bundled in the stock
+  user config** (`~/.config/blender/4.0`) and works headless — verified via the
-  binary — an agent cannot assume it is present; check and tell the user if a
+  flake's `blender-4.0.2 --background`. `wgt01/generator/export_mdl.py` drives it
-  real MDL export is requested.
+  (see below). If working on another machine, don't assume it's present; check
+  `addon_utils.enable("neverblender")` and tell the user.
+  Key facts: root = Empty `nvb.emptytype='dummy'` + `nvb.classification='tile'`
+  (name == resref); geometry meshes `nvb.meshtype='trimesh'`; one walkmesh mesh
+  `nvb.meshtype='aabb'`. Walkmesh face surfacemat = the mesh's material *slot*
+  index after `nvb_utils.create_wok_materials(mesh)` fills slots 0..22 in
+  `nvb_def.wok_materials` order (walkable Stone=4, Nonwalk=7). Export:
+  `scene.nvb_mdlexport(filepath=..., export_walkmesh=True)` on the active scene.
 - **cleanmodels** — cleans/optimizes ASCII MDL, fixes common walkmesh problems.
 - **neverwinter-nim** — CLI (`nwn_erf`, `nwn_gff`, …): pack the `.hak`/ERF, and
   read/write GFF (the `.itp` is GFF).
 - **blender-mcp-nwn** (see `/nix/nixos/blender-mcp-nwn`) — MCP server exposing
   `run_blender_script`, `read_blend_metadata`, `export_for_nwn` so Claude can
   drive Blender 4.0.2 headless against these `.blend` sources.
+- **wgt01 generator kit** (`wgt01/generator/`, driven by `wgt01/flake.nix` apps):
+  `build.py` (`nix run .#build`) builds the `.blend` tile library from the shared
+  `tiles.py` table; `export_mdl.py` (`nix run .#export -- <blend> <outdir>`)
+  exports real `.mdl`+`.wok` per tile via NeverBlender; `make_wok.py`
+  (`nix run .#wok`) and `make_set.py` (`nix run .#set`) are pure-Python (no
+  Blender) emitters — an ASCII `.wok` fallback (format validated against
+  NeverBlender's own output) and a first-pass `.set`.
 
 ### 6.2 Build → export → pack
 1. **Generate `.blend` source** — `nix run .#build -- out.blend` (or drive via the
@@ -353,9 +367,14 @@ tracks Blender 3.x–4.x, **not** nixpkgs' Blender 5.x. Do not "upgrade" it.
 - **Custom doors not in `doortypes.2da`** (and not merged/shipped) → blank doors.
 - **`Transition=0`** disables adjacent placement of groups/features.
 - **Group first tile `-1` or non-unique filename** → crash / no autopick.
-- **NeverBlender not installed** in this Blender → `export_for_nwn` gives you
+- **NeverBlender walkmesh surfacemat** comes from the face's material *slot*
-  OBJ/FBX + an `mdl.json` config, **not** a real `.mdl`. Install the addon for
+  index, **not** the material name — you must call
-  true MDL/WOK export; say so rather than claiming MDL output.
+  `nvb_utils.create_wok_materials(mesh)` first (fills slots 0..22) then set each
+  face's `material_index` to the surfacemat id. Naming a lone material `wok_Stone`
+  is silently ignored (falls back to slot order). `export_mdl.py` does this right.
+- **NeverBlender not installed** (other machines) → `export_for_nwn` gives you
+  OBJ/FBX + an `mdl.json` config, **not** a real `.mdl`. Use `make_wok.py` for an
+  ASCII `.wok` fallback, or install the addon; say so rather than claiming MDL.
 - **Don't upgrade Blender past 4.x** here — breaks NeverBlender/cleanmodels.
 
 ---

wgt01/flake.nix

@@ -44,6 +44,20 @@
         runtimeInputs = [ py ];
         text = ''exec python ${gen}/make_wok.py "$@"'';
       };
+
+      # Real .mdl + .wok export via the Neverblender addon (must be enabled in
+      # this Blender's user config — confirmed working headless).
+      mkmdl = pkgs.writeShellApplication {
+        name = "wgt-export";
+        runtimeInputs = [ blender ];
+        text = ''
+          blend="''${1:?usage: wgt-export <blend> <outdir> [CODE...]}"
+          outdir="''${2:-mdl}"
+          shift 2 || true
+          exec blender-4.0.2 --background "$blend" --python ${gen}/export_mdl.py \
+            --python-exit-code 1 -- "$outdir" "$@"
+        '';
+      };
     in
     {
       packages.${system}.default = build;
@@ -65,6 +79,10 @@
           type = "app";
           program = "${mkwok}/bin/wgt-wok";
         };
+        export = {
+          type = "app";
+          program = "${mkmdl}/bin/wgt-export";
+        };
       };
 
       devShells.${system}.default = pkgs.mkShell {

wgt01/generator/export_mdl.py

@@ -0,0 +1,103 @@
+"""Export every tile to real NWN ASCII .mdl + .wok via Neverblender (Blender 4.0.2).
+
+    blender-4.0.2 --background <built.blend> --python export_mdl.py -- <outdir> [CODE ...]
+
+Requires the Neverblender addon enabled in this Blender (Import-Export:
+Neverblender). Confirmed working headless against ~/.config/blender/4.0. For each
+tile it assembles a Neverblender-native model in its own scene — an AuroraBase
+(Empty, classification TILE, name == resref), a trimesh child (the VIS geometry),
+and one aabb walkmesh child (from tiles.wok_quads) — then calls
+scene.nvb_mdlexport(export_walkmesh=True) to emit <resref>.mdl and <resref>.wok.
+
+Walkmesh surface materials use Neverblender's name->surfacemat mapping
+(nvb_def.wok_materials): walkable faces = wok_Stone (idx 4), blockers = wok_Nonwalk
+(idx 7). Refine per tile later (wok_Water/wok_StoneBridge/etc.) if desired.
+"""
+
+import os
+import sys
+
+import bpy
+import addon_utils
+
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+import tiles  # noqa: E402
+
+# Neverblender writes each walkmesh face's material_index (slot) verbatim as the
+# surfacemat id (nvb_node.py), and create_wok_materials() fills slots 0..22 in
+# nvb_def.wok_materials order. So the slot index IS the surfacemat index:
+WALK_SURF = 4    # wok_Stone
+BLOCK_SURF = 7   # wok_Nonwalk
+
+
+def build_wok(spec, name):
+    from neverblender import nvb_utils
+    quads = tiles.wok_quads(spec)
+    verts, faces, surf = [], [], []
+    for quad, walk in quads:
+        b = len(verts)
+        verts += quad
+        faces.append((b, b + 1, b + 2, b + 3))
+        surf.append(WALK_SURF if walk else BLOCK_SURF)
+    me = bpy.data.meshes.new(name)
+    me.from_pydata(verts, [], faces)
+    nvb_utils.create_wok_materials(me)          # slots 0..22 == wok_materials order
+    me.update()
+    for poly, s in zip(me.polygons, surf):
+        poly.material_index = s                 # slot == surfacemat id on export
+    ob = bpy.data.objects.new(name, me)
+    ob.nvb.meshtype = "aabb"
+    return ob
+
+
+def export_tile(spec, outdir):
+    ref = tiles.resref(spec)
+    vis = bpy.data.objects.get("VIS_" + spec["code"])
+    if vis is None:
+        return {"code": spec["code"], "ok": False, "error": "missing VIS object"}
+
+    scn = bpy.data.scenes.new("exp_" + spec["code"])
+    bpy.context.window.scene = scn
+
+    root = bpy.data.objects.new(ref, None)          # AuroraBase; name == filename
+    root.nvb.emptytype = "dummy"
+    root.nvb.classification = "tile"
+    scn.collection.objects.link(root)
+
+    v = vis.copy()
+    v.data = vis.data.copy()
+    v.name = ref + "_01"
+    v.nvb.meshtype = "trimesh"
+    scn.collection.objects.link(v)
+    v.parent = root
+
+    w = build_wok(spec, ref + "_wg")                # single aabb walkmesh (rule: 1 per tile)
+    scn.collection.objects.link(w)
+    w.parent = root
+
+    mdl = os.path.join(outdir, ref + ".mdl")
+    bpy.ops.scene.nvb_mdlexport(filepath=mdl, export_walkmesh=True,
+                                check_existing=False, batch_mode="OFF")
+    wok = os.path.join(outdir, ref + ".wok")
+    return {"code": spec["code"], "ref": ref, "ok": os.path.isfile(mdl),
+            "mdl": os.path.isfile(mdl), "wok": os.path.isfile(wok)}
+
+
+def main():
+    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    outdir = os.path.abspath(argv[0]) if argv else os.path.abspath("mdl")
+    only = set(argv[1:])
+    os.makedirs(outdir, exist_ok=True)
+
+    addon_utils.enable("neverblender", default_set=False)
+
+    results = [export_tile(s, outdir) for s in tiles.TILES if not only or s["code"] in only]
+    ok = sum(1 for r in results if r["ok"])
+    bad = [r for r in results if not r["ok"]]
+    print(f"EXPORTED {ok}/{len(results)} tiles -> {outdir}")
+    if bad:
+        print("FAILED:", bad)
+
+
+if __name__ == "__main__":
+    main()