CosmicClash/tools/blender/gen_ship.py

"""Procedurally generates the Cosmic Clash ship hull model.

Run inside Blender (e.g. via the blender-mcp `execute_blender_code` tool, or
Blender's own script editor / `blender --background --python gen_ship.py`).
Builds six named mesh objects — Hull, Nose, Canopy, TailFin, EngineGlowL,
EngineGlowR — greebled from bmesh primitives (bevel + inset/extrude), saves
ship.blend, then exports each part as its OWN glb file (ship_hull.glb,
ship_nose.glb, etc.) rather than one combined file.

Why per-part files: Godot cannot reliably resolve a single named sub-mesh
out of a multi-object glTF via `path.glb::ArrayMesh_xxx` addressing from a
*different* .tscn — that syntax only resolves once the whole glTF scene has
already been instanced elsewhere in the same session; a fresh load of just
that ext_resource reference silently returns a null mesh. Exporting one
object per glb file avoids that (each file's root is a clean, individually
loadable node), but each still imports as a synthetic Node3D wrapper with
ONE MeshInstance3D child — not the MeshInstance3D itself. `ship.tscn` needs
the mesh nodes as *direct* children of the Ship root (see node-name note
below), so after running this script, run `extract_meshes.gd` (in this same
directory) inside Godot to pull each part's ArrayMesh out into its own
`.res` file — that's what `ship.tscn` actually references.

Node names matter: `scripts/ship.gd`'s `_apply_team_color()` recolors direct
children of the Ship node named exactly "Nose" and "TailFin" at runtime, so
those two object names must be preserved.

Orientation: empirically, Blender's -Y axis (this script builds the nose at
-Y) maps to Godot's **+Z** on glTF export (not -Z as the naive Blender-Z-up
vs. Godot-Y-up mapping might suggest) — verified in-engine, not assumed.
Since ship forward is Godot -Z (see `ship.gd`), `ship.tscn` applies a
180-degree rotation (`Transform3D(-1,0,0, 0,1,0, 0,0,-1, ...)`) to every
part's instance node to correct this. If you regenerate the parts, that
correction stays in `ship.tscn` — don't rebuild it into the Blender geometry
too, or the two fixes will cancel out and the ship will face backwards again.

Silhouette budget: the ship's RigidBody3D collision shape (`ship.tscn`,
BoxShape3D) is (1, 1, 4) in Godot space — X width, Y height, Z length. In
this script's local (pre-export) space X=width, Y=length (nose at -Y),
Z=height, and the budget is X +-0.5, Y(length) +-2.0, Z(height) +-0.5. The
built silhouette is kept reasonably close to that budget, not an exact fit
(matching the original primitive ship, which was also slightly over at a
few extremities).
"""

import math
import random

import bmesh
import bpy
from mathutils import Matrix, Vector

BLEND_PATH = "Game/assets/blender_models/ship.blend"
PART_GLB_PATHS = {
    "Hull": "Game/assets/models/ship_hull.glb",
    "Nose": "Game/assets/models/ship_nose.glb",
    "Canopy": "Game/assets/models/ship_canopy.glb",
    "TailFin": "Game/assets/models/ship_tailfin.glb",
    "EngineGlowL": "Game/assets/models/ship_engine_l.glb",
    "EngineGlowR": "Game/assets/models/ship_engine_r.glb",
}


def new_mesh_object(name, bm):
    mesh = bpy.data.meshes.new(name)
    bm.to_mesh(mesh)
    bm.free()
    obj = bpy.data.objects.new(name, mesh)
    bpy.context.collection.objects.link(obj)
    return obj


def remove_object(name):
    obj = bpy.data.objects.get(name)
    if obj:
        mesh = obj.data
        bpy.data.objects.remove(obj, do_unlink=True)
        if mesh.users == 0:
            bpy.data.meshes.remove(mesh)


def clear_scene():
    for obj in list(bpy.data.objects):
        if obj.type in {"MESH", "EMPTY"}:
            bpy.data.objects.remove(obj, do_unlink=True)
    for block in list(bpy.data.meshes):
        if block.users == 0:
            bpy.data.meshes.remove(block)
    for block in list(bpy.data.materials):
        if block.users == 0:
            bpy.data.materials.remove(block)


def build_hull():
    random.seed(7)
    bm = bmesh.new()
    bmesh.ops.create_cube(bm, size=1.0)
    # Full dims: width 0.9, length 2.6, height 0.6 (collision budget is 1 x 4 x 1 full)
    bmesh.ops.scale(bm, vec=(0.9, 2.6, 0.6), verts=bm.verts)

    bm.edges.ensure_lookup_table()
    long_edges = [e for e in bm.edges if (e.verts[0].co - e.verts[1].co).length > 2.0]
    bmesh.ops.bevel(bm, geom=long_edges, offset=0.1, segments=3, affect="EDGES")

    bm.faces.ensure_lookup_table()
    panel_target_faces = [f for f in bm.faces if abs(f.normal.z) > 0.6 or abs(f.normal.x) > 0.6]
    edges_to_cut = list({e for f in panel_target_faces for e in f.edges})
    bmesh.ops.subdivide_edges(bm, edges=edges_to_cut, cuts=3, use_grid_fill=True)

    def greeble_pass(seed, fraction, thickness, depth_range):
        random.seed(seed)
        bm.faces.ensure_lookup_table()
        candidates = [
            f
            for f in bm.faces
            if (abs(f.normal.z) > 0.55 or abs(f.normal.x) > 0.55) and 0.01 < f.calc_area() < 0.35
        ]
        random.shuffle(candidates)
        chosen = candidates[: max(1, int(len(candidates) * fraction))]
        for f in chosen:
            if not f.is_valid:
                continue
            res = bmesh.ops.inset_individual(bm, faces=[f], thickness=thickness)
            new_faces = res["faces"]
            if new_faces:
                nf = new_faces[0]
                depth = random.uniform(*depth_range)
                bmesh.ops.translate(bm, verts=nf.verts, vec=nf.normal * depth)

    greeble_pass(seed=7, fraction=1 / 3, thickness=0.02, depth_range=(-0.03, 0.022))
    greeble_pass(seed=42, fraction=0.25, thickness=0.018, depth_range=(-0.028, 0.018))

    bmesh.ops.recalc_face_normals(bm, faces=bm.faces)
    return new_mesh_object("Hull", bm)


def build_nose():
    random.seed(11)
    bm = bmesh.new()
    bmesh.ops.create_cube(bm, size=1.0)
    bmesh.ops.scale(bm, vec=(0.82, 0.25, 0.5), verts=bm.verts)
    bmesh.ops.translate(bm, vec=(0.0, -1.425, 0.0), verts=bm.verts)

    def front_face():
        bm.faces.ensure_lookup_table()
        return min(bm.faces, key=lambda f: f.calc_center_median().y)

    # Stage 1 taper: extrude forward, narrow to ~half width/height.
    f = front_face()
    r = bmesh.ops.extrude_face_region(bm, geom=[f])
    new_verts = [v for v in r["geom"] if isinstance(v, bmesh.types.BMVert)]
    bmesh.ops.translate(bm, verts=new_verts, vec=(0, -0.32, 0.02))
    pivot = sum((v.co for v in new_verts), Vector()) / len(new_verts)
    bmesh.ops.scale(bm, verts=new_verts, vec=(0.5, 1.0, 0.55), space=Matrix.Translation(-pivot))

    # Stage 2 taper: extrude further to a near-point tip.
    bm.faces.ensure_lookup_table()
    f2 = front_face()
    r2 = bmesh.ops.extrude_face_region(bm, geom=[f2])
    new_verts2 = [v for v in r2["geom"] if isinstance(v, bmesh.types.BMVert)]
    bmesh.ops.translate(bm, verts=new_verts2, vec=(0, -0.28, 0.0))
    pivot2 = sum((v.co for v in new_verts2), Vector()) / len(new_verts2)
    bmesh.ops.scale(bm, verts=new_verts2, vec=(0.08, 1.0, 0.08), space=Matrix.Translation(-pivot2))

    bm.edges.ensure_lookup_table()
    sharp_edges = [e for e in bm.edges if e.calc_face_angle(1.0) > 0.35]
    bmesh.ops.bevel(bm, geom=sharp_edges, offset=0.02, segments=2, affect="EDGES")

    bm.faces.ensure_lookup_table()
    side_faces = [f for f in bm.faces if abs(f.normal.x) > 0.5 and f.calc_area() > 0.01][:2]
    for f in side_faces:
        if not f.is_valid:
            continue
        res = bmesh.ops.inset_individual(bm, faces=[f], thickness=0.02)
        nf = res["faces"][0] if res["faces"] else None
        if nf:
            bmesh.ops.translate(bm, verts=nf.verts, vec=nf.normal * -0.015)

    bmesh.ops.recalc_face_normals(bm, faces=bm.faces)
    return new_mesh_object("Nose", bm)


def build_canopy():
    bm = bmesh.new()
    bmesh.ops.create_icosphere(bm, subdivisions=2, radius=0.3)
    bm.faces.ensure_lookup_table()
    faces_to_del = [f for f in bm.faces if f.calc_center_median().z < -0.02]
    bmesh.ops.delete(bm, geom=faces_to_del, context="FACES")
    bm.edges.ensure_lookup_table()
    boundary_edges = [e for e in bm.edges if len(e.link_faces) == 1]
    if boundary_edges:
        bmesh.ops.holes_fill(bm, edges=boundary_edges)
    bmesh.ops.recalc_face_normals(bm, faces=bm.faces)

    # Swept teardrop canopy: wider, stretched fore-aft, low profile, tapered at the rear.
    for v in bm.verts:
        v.co.x *= 1.5
        v.co.y *= 2.2
        v.co.z *= 0.82
        if v.co.y > 0:
            t = min(v.co.y / 0.62, 1.0)
            v.co.z *= 1.0 - 0.35 * t
            v.co.x *= 1.0 - 0.25 * t

    obj = new_mesh_object("Canopy", bm)
    # Front-upper on the hull; kept low so the top stays close to the +-0.5 height budget.
    obj.location = (0.0, -0.55, 0.31)
    return obj


def build_nacelle(name, x_offset):
    bm = bmesh.new()
    bmesh.ops.create_cone(
        bm, cap_ends=True, cap_tris=False, segments=12, radius1=0.11, radius2=0.095, depth=0.85
    )
    # Cone is built along Z by default; rotate -90 deg about X to align its axis with Y (length).
    rot = Matrix.Rotation(-math.pi / 2, 4, "X")
    bmesh.ops.transform(bm, matrix=rot, verts=bm.verts)

    bm.edges.ensure_lookup_table()
    ring_edges = [
        e
        for e in bm.edges
        if len(e.link_faces) == 2 and abs(e.verts[0].co.y - e.verts[1].co.y) < 0.01
    ]
    if ring_edges:
        bmesh.ops.bevel(bm, geom=ring_edges, offset=0.012, segments=2, affect="EDGES")

    obj = new_mesh_object(name, bm)
    # Rear of the ship, flanking the hull, slightly below centerline.
    obj.location = (x_offset, 0.95, -0.05)
    return obj


def build_tailfin():
    bm = bmesh.new()
    bmesh.ops.create_cube(bm, size=1.0)
    bmesh.ops.scale(bm, vec=(0.06, 0.65, 0.42), verts=bm.verts)
    # Sweep the top-rear edge back, taper the top edge thin.
    for v in bm.verts:
        if v.co.z > 0:
            v.co.y += 0.16 if v.co.y > 0 else 0.04
            v.co.x *= 0.35

    bm.edges.ensure_lookup_table()
    sharp_edges = [e for e in bm.edges if e.calc_face_angle(1.0) > 0.3]
    bmesh.ops.bevel(bm, geom=sharp_edges, offset=0.012, segments=2, affect="EDGES")
    bmesh.ops.recalc_face_normals(bm, faces=bm.faces)

    obj = new_mesh_object("TailFin", bm)
    obj.location = (0.0, 0.72, 0.24)
    return obj


def make_material(name, base_rgb, metallic, roughness, emission_rgb=None, emission_strength=0.0):
    existing = bpy.data.materials.get(name)
    if existing:
        bpy.data.materials.remove(existing)
    mat = bpy.data.materials.new(name)
    mat.use_nodes = True
    bsdf = mat.node_tree.nodes.get("Principled BSDF")
    bsdf.inputs["Base Color"].default_value = (*base_rgb, 1.0)
    bsdf.inputs["Metallic"].default_value = metallic
    bsdf.inputs["Roughness"].default_value = roughness
    if emission_rgb is not None:
        bsdf.inputs["Emission Color"].default_value = (*emission_rgb, 1.0)
        bsdf.inputs["Emission Strength"].default_value = emission_strength
    return mat


def assign_materials():
    mat_hull = make_material("Mat_Hull", (0.35, 0.37, 0.42), 0.6, 0.4)
    # Accent starts team-blue; Ship._apply_team_color() overrides this per-team at runtime.
    mat_accent = make_material("Mat_Accent", (0.25, 0.55, 1.0), 0.3, 0.5, (0.25, 0.55, 1.0), 0.9)
    mat_canopy = make_material("Mat_Canopy", (0.15, 0.85, 1.0), 0.8, 0.1, (0.15, 0.85, 1.0), 1.4)
    mat_nacelle_body = make_material("Mat_NacelleBody", (0.22, 0.24, 0.28), 0.7, 0.35)
    mat_engine_glow = make_material(
        "Mat_EngineGlow", (1.0, 0.55, 0.15), 0.1, 0.4, (1.0, 0.55, 0.15), 4.0
    )

    def assign_single(obj_name, mat):
        obj = bpy.data.objects[obj_name]
        obj.data.materials.clear()
        obj.data.materials.append(mat)

    assign_single("Hull", mat_hull)
    assign_single("Nose", mat_accent)
    assign_single("TailFin", mat_accent)
    assign_single("Canopy", mat_canopy)

    for name in ["EngineGlowL", "EngineGlowR"]:
        obj = bpy.data.objects[name]
        obj.data.materials.clear()
        obj.data.materials.append(mat_nacelle_body)  # slot 0: body
        obj.data.materials.append(mat_engine_glow)  # slot 1: rear exhaust glow cap
        polys = obj.data.polygons
        max_y = max(p.center.y for p in polys)
        for p in polys:
            p.material_index = 1 if p.center.y > max_y - 0.01 else 0


def build_ship():
    clear_scene()
    build_hull()
    build_nose()
    build_canopy()
    build_nacelle("EngineGlowL", -0.42)
    build_nacelle("EngineGlowR", 0.42)
    build_tailfin()
    assign_materials()


def export(repo_root):
    import os

    blend_path = os.path.join(repo_root, BLEND_PATH)
    bpy.ops.wm.save_as_mainfile(filepath=blend_path)

    for obj_name, rel_path in PART_GLB_PATHS.items():
        bpy.ops.object.select_all(action="DESELECT")
        obj = bpy.data.objects[obj_name]
        obj.select_set(True)
        bpy.context.view_layer.objects.active = obj
        bpy.ops.export_scene.gltf(
            filepath=os.path.join(repo_root, rel_path),
            export_format="GLB",
            use_selection=True,
            export_apply=True,
            export_materials="EXPORT",
        )

    print("Exported per-part glbs. Now run extract_meshes.gd inside Godot")
    print("to produce the ship_*.res files that ship.tscn references.")


if __name__ == "__main__":
    import os

    # Assumes this script lives at <repo_root>/tools/blender/gen_ship.py.
    repo_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
    build_ship()
    export(repo_root)