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>

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()