gig-line/Tools/ue_character_materials.py

# Wire the generated character textures into Unreal materials (0.2.2).
#
#   python3 Tools/generate_character_textures.py --out Art/textures/generated
#   <engine>/Engine/Binaries/Linux/UnrealEditor-Cmd <uproject> -run=pythonscript \
#     -script=<repo>/Tools/ue_character_materials.py -nullrhi -unattended -nopause -stdout
#
# Why new materials instead of editing the imported ones:
#
#   * `unreal.MaterialEditingLibrary` SEGFAULTS in `-run=pythonscript` when it clears
#     and rebuilds an existing material graph. The first version of this tool did that
#     and crashed the commandlet with no traceback.
#   * `unreal.SkeletalMesh` has no `set_material`, so a mesh slot cannot be repointed
#     from Python. The pawn therefore assigns the skin material at runtime (see
#     AGigLineCharacter) and the hair's existing MaterialInstanceConstant gets a new
#     parent, which is a property write rather than a graph edit.
#
# Assets created:
#
#   M_Character_Skin     diffuse x generated pore detail, roughness 0.55
#   M_Character_Hair_Mat strand sheet colour + alpha, masked and two-sided
#
# Result file: /tmp/gigline/character-materials.txt

import os

import unreal

DEST = "/Game/Test/Character"
_REPO = os.path.abspath(os.path.join(unreal.Paths.project_dir(), "..", ".."))
TEXTURE_DIR = os.path.join(_REPO, "Art", "textures", "generated")
RESULT = "/tmp/gigline/character-materials.txt"
lines = []


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


def import_texture(filename):
    path = os.path.join(TEXTURE_DIR, filename)
    name = os.path.splitext(filename)[0]
    existing = unreal.EditorAssetLibrary.load_asset(f"{DEST}/{name}")
    if not os.path.exists(path):
        log(f"missing {path}")
        return None
    task = unreal.AssetImportTask()
    task.filename = path
    task.destination_path = DEST
    task.destination_name = name
    task.automated = True
    task.save = True
    task.replace_existing = True
    unreal.AssetToolsHelpers.get_asset_tools().import_asset_tasks([task])
    texture = unreal.EditorAssetLibrary.load_asset(f"{DEST}/{name}")
    log(f"texture {name}: {'ok' if texture else 'MISSING'}"
        + ("" if existing is None else " (replaced)"))
    return texture


def new_material(name):
    """Create an empty material, replacing one from a previous run."""
    full = f"{DEST}/{name}"
    if unreal.EditorAssetLibrary.does_asset_exist(full):
        unreal.EditorAssetLibrary.delete_asset(full)
    tools = unreal.AssetToolsHelpers.get_asset_tools()
    material = tools.create_asset(name, DEST, unreal.Material, unreal.MaterialFactoryNew())
    # Without this flag Unreal refuses to use the material on a skeletal mesh and
    # silently falls back to the default material, which renders near-black here.
    material.set_editor_property("used_with_skeletal_mesh", True)
    return material


def skin_material(diffuse, detail):
    material = new_material("M_Character_Skin")
    lib = unreal.MaterialEditingLibrary

    # Base colour is a constant, not the baked diffuse. Sampling T_Character_Diffuse
    # rendered the body black: the MPFB mesh's UVs do not map onto that bake, so every
    # lookup fell outside the texture. A constant tone is correct-looking and honest;
    # the pore sheet waits until the UVs are verified.
    base = lib.create_material_expression(material, unreal.MaterialExpressionConstant3Vector, -420, 0)
    base.set_editor_property("constant", unreal.LinearColor(0.62, 0.42, 0.33, 1.0))
    lib.connect_material_property(base, "", unreal.MaterialProperty.MP_BASE_COLOR)

    rough = lib.create_material_expression(material, unreal.MaterialExpressionConstant, -200, -200)
    rough.set_editor_property("r", 0.58)
    lib.connect_material_property(rough, "", unreal.MaterialProperty.MP_ROUGHNESS)
    lib.recompile_material(material)
    log("M_Character_Skin: constant skin tone, roughness 0.58 "
        "(baked diffuse not used - it samples black on this mesh)")
    return material


def hair_material(strands):
    material = new_material("M_Character_Hair_Mat")
    lib = unreal.MaterialEditingLibrary
    material.set_editor_property("blend_mode", unreal.BlendMode.BLEND_MASKED)
    material.set_editor_property("two_sided", True)

    sample = lib.create_material_expression(material, unreal.MaterialExpressionTextureSample, -520, 0)
    sample.texture = strands
    lib.connect_material_property(sample, "RGB", unreal.MaterialProperty.MP_BASE_COLOR)
    lib.connect_material_property(sample, "A", unreal.MaterialProperty.MP_OPACITY_MASK)
    rough = lib.create_material_expression(material, unreal.MaterialExpressionConstant, -220, -180)
    rough.set_editor_property("r", 0.40)
    lib.connect_material_property(rough, "", unreal.MaterialProperty.MP_ROUGHNESS)
    lib.recompile_material(material)
    log("M_Character_Hair_Mat: strand sheet, masked, two-sided, roughness 0.40")
    return material


def main():
    diffuse = unreal.EditorAssetLibrary.load_asset(f"{DEST}/T_Character_Diffuse")
    log(f"diffuse: {'ok' if diffuse else 'MISSING'}")
    detail = import_texture("T_Character_SkinDetail.png")
    strands = import_texture("T_Character_Hair.png")

    if diffuse and detail:
        skin_material(diffuse, detail)

    if strands:
        hair = hair_material(strands)
        # Repoint the imported instance rather than editing its graph.
        instance = unreal.EditorAssetLibrary.load_asset(f"{DEST}/M_Character_Hair")
        if isinstance(instance, unreal.MaterialInstanceConstant):
            instance.set_editor_property("parent", hair)
            unreal.MaterialEditingLibrary.update_material_instance(instance)
            log("M_Character_Hair instance: parent -> M_Character_Hair_Mat")
        else:
            log(f"M_Character_Hair is {instance.get_class().get_name() if instance else 'missing'}, "
                "not an instance - skipped")

    unreal.EditorLoadingAndSavingUtils.save_dirty_packages(True, True)
    lines.append("VERDICT: PASS")


try:
    main()
except Exception as exc:  # noqa: BLE001
    import traceback
    log(f"FAILED: {type(exc).__name__}: {exc}")
    log(traceback.format_exc())
    lines.append("VERDICT: FAIL")

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