gig-line/Tools/mpfb_character_export.py

# MPFB character export for the Blender -> Unreal pipeline (0.1.0 acceptance).
#
# Generates a default human, adds the standard deform rig with weights,
# materializes the v2 skin, bakes its diffuse to a texture, and exports
# FBX with the named export preset "ue_character_v1".
#
#   blender -b --factory-startup --python Tools/mpfb_character_export.py -- \
#     --out /tmp/gigline/character.fbx \
#     --save-blend Art/blender/character/character-<date>.blend

import argparse
import os
import sys

import bpy

REPORT = "/tmp/mpfb-export-report.txt"
lines = []


def log(msg):
    lines.append(str(msg))


def enable_mpfb():
    bpy.ops.preferences.addon_enable(module="bl_ext.blender_org.mpfb")
    assert "bl_ext.blender_org.mpfb" in bpy.context.preferences.addons, "MPFB did not enable"


def build_character():
    for obj in list(bpy.data.objects):
        bpy.data.objects.remove(obj, do_unlink=True)

    bpy.ops.mpfb.create_human("EXEC_DEFAULT")
    human = bpy.context.active_object
    log(f"create_human: {human.name}, {len(human.data.vertices)} verts, dims={[round(d, 3) for d in human.dimensions]}")

    bpy.ops.mpfb.add_standard_rig("EXEC_DEFAULT")
    armatures = [o for o in bpy.data.objects if o.type == "ARMATURE"]
    log(f"add_standard_rig: {len(armatures)} armature(s), bones={[len(a.data.bones) for a in armatures]}")

    bpy.ops.object.select_all(action="DESELECT")
    human.select_set(True)
    bpy.context.view_layer.objects.active = human
    bpy.ops.mpfb.create_v2_skin("EXEC_DEFAULT")
    mats = [m.name for m in human.data.materials]
    log(f"create_v2_skin: materials={mats}")
    return human


def bake_diffuse(human, size=1024):
    mat = human.data.materials[0]
    nodes, links = mat.node_tree.nodes, mat.node_tree.links

    img = bpy.data.images.new("T_Skin_Diffuse", size, size)
    tex_node = nodes.new("ShaderNodeTexImage")
    tex_node.image = img
    nodes.active = tex_node
    tex_node.select = True

    bsdf = next((n for n in nodes if n.type == "BSDF_PRINCIPLED"), None)
    bsdf_input = bsdf.inputs["Base Color"] if bsdf else None
    if bsdf is not None:
        for link in list(links):
            if link.to_node == bsdf and link.to_socket == bsdf_input:
                links.remove(link)
        links.new(tex_node.outputs["Color"], bsdf_input)

    scene = bpy.context.scene
    scene.render.engine = "CYCLES"
    scene.cycles.device = "CPU"
    scene.cycles.samples = 1
    scene.render.bake.use_pass_direct = False
    scene.render.bake.use_pass_indirect = False
    scene.render.bake.use_pass_color = True
    scene.render.bake.margin = 8

    bpy.ops.object.select_all(action="DESELECT")
    human.select_set(True)
    bpy.context.view_layer.objects.active = human
    bpy.ops.object.bake(type="DIFFUSE", pass_filter={"COLOR"}, use_clear=True)
    img.filepath = "/tmp/gigline/T_Skin_Diffuse.png"
    img.filepath_raw = img.filepath
    img.file_format = "PNG"
    img.save()
    log(f"bake: baked {size}x{size} diffuse -> {img.filepath} (filepath now set for FBX)")

    # MPFB's v2 skin is a node-group tree the FBX exporter cannot map to a
    # texture. Build a flat export material carrying the baked diffuse so the
    # FBX (and therefore Unreal) gets a real texture.
    export_mat = bpy.data.materials.new("M_Character_Export")
    export_mat.use_nodes = True
    nt = export_mat.node_tree
    nt.nodes.clear()
    out = nt.nodes.new("ShaderNodeOutputMaterial")
    bsdf = nt.nodes.new("ShaderNodeBsdfPrincipled")
    tex = nt.nodes.new("ShaderNodeTexImage")
    tex.image = img
    nt.links.new(tex.outputs["Color"], bsdf.inputs["Base Color"])
    nt.links.new(bsdf.outputs["BSDF"], out.inputs["Surface"])
    human.data.materials.clear()
    human.data.materials.append(export_mat)
    log("export material: M_Character_Export with baked texture assigned")


def export_fbx(human, path):
    os.makedirs(os.path.dirname(path), exist_ok=True)
    # Named export preset "ue_character_v1" — change only via a new preset name.
    bpy.ops.export_scene.fbx(
        filepath=path,
        use_selection=False,
        object_types={"ARMATURE", "MESH"},
        apply_unit_scale=True,
        apply_scale_options="FBX_SCALE_NONE",
        axis_forward="-Y",
        axis_up="Z",
        use_space_transform=True,
        use_mesh_modifiers=True,
        add_leaf_bones=False,
        path_mode="COPY",
        embed_textures=False,
        mesh_smooth_type="OFF",
        bake_space_transform=False,
    )
    log(f"export: FBX preset ue_character_v1 -> {path}")


def main():
    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
    parser = argparse.ArgumentParser()
    parser.add_argument("--out", default="/tmp/gigline/character.fbx")
    parser.add_argument("--save-blend", default=None)
    args = parser.parse_args(argv)

    enable_mpfb()
    human = build_character()
    bake_diffuse(human)
    if args.save_blend:
        os.makedirs(os.path.dirname(args.save_blend), exist_ok=True)
        bpy.ops.wm.save_as_mainfile(filepath=args.save_blend)
        log(f"save: {args.save_blend}")
    export_fbx(human, args.out)

    with open(REPORT, "w") as f:
        f.write("\n".join(lines) + "\n")


main()