Engraves an SVG pattern onto the surface of an STL model using Blender’s Python API with shrinkwrap, solidify, and boolean modifiers.

wrap_pattern_stl.py

"""
Usage:
    blender --background --python wrap_pattern.py -- \
        --stl flask.stl \
        --svg pattern.svg \
        --output flask_wrapped.stl

    Notes:
      - The -- is required before the Python script arguments.
      - All paths are relative to this script's directory or absolute.
      - Output will be written to --output (default: flask_wrapped.stl).

    Requires:
      - Blender 2.80+
      - Built-in Python modules only (no pip install required)
"""

import bpy
import os
import sys
import argparse

# --- PARSE ARGS ---
def parse_args():
    argv = sys.argv
    if "--" in argv:
        argv = argv[argv.index("--") + 1:]
    else:
        argv = []

    parser = argparse.ArgumentParser(description="Engrave SVG pattern onto STL surface using Blender")
    parser.add_argument("--stl", required=True, help="Path to STL model")
    parser.add_argument("--svg", required=True, help="Path to SVG pattern")
    parser.add_argument("--output", default="flask_wrapped.stl", help="Output STL filename")
    parser.add_argument("--verbose", action="store_true", help="Enable verbose output")

    return parser.parse_args()

# --- MAIN ---
def main():
    args = parse_args()

    # --- RESOLVE PATHS ---
    script_dir = os.path.dirname(os.path.abspath(__file__))
    stl_path = os.path.abspath(os.path.join(script_dir, args.stl))
    svg_path = os.path.abspath(os.path.join(script_dir, args.svg))
    output_path = os.path.abspath(os.path.join(script_dir, args.output))

    # --- LOGGING ---
    if args.verbose:
        print(f"STL Path: {stl_path}")
        print(f"SVG Path: {svg_path}")
        print(f"Output Path: {output_path}")

    # --- CLEAR SCENE ---
    bpy.ops.wm.read_factory_settings(use_empty=True)

    # --- IMPORT STL ---
    bpy.ops.import_mesh.stl(filepath=stl_path)
    stl_obj = bpy.context.selected_objects[0]
    stl_obj.name = "BaseModel"

    # --- IMPORT SVG ---
    bpy.ops.import_curve.svg(filepath=svg_path)
    svg_objs = [obj for obj in bpy.context.selected_objects if obj.type == 'CURVE']

    # Convert SVG curves to mesh
    mesh_objs = []
    for curve_obj in svg_objs:
        bpy.context.view_layer.objects.active = curve_obj
        curve_obj.select_set(True)
        bpy.ops.object.convert(target='MESH')
        mesh_objs.append(curve_obj)

    # Join all SVG parts into one object
    for obj in bpy.context.selected_objects:
        obj.select_set(False)
    for obj in mesh_objs:
        obj.select_set(True)
    bpy.context.view_layer.objects.active = mesh_objs[0]
    bpy.ops.object.join()
    pattern_obj = bpy.context.active_object
    pattern_obj.name = "Pattern"

    # --- POSITION & WRAP ---
    pattern_obj.location.z += 0.01  # ensure slight contact

    shrinkwrap = pattern_obj.modifiers.new(name="Shrinkwrap", type='SHRINKWRAP')
    shrinkwrap.target = stl_obj
    shrinkwrap.wrap_method = 'PROJECT'
    shrinkwrap.wrap_mode = 'ON_SURFACE'
    shrinkwrap.use_negative_direction = True
    shrinkwrap.use_positive_direction = True
    shrinkwrap.offset = 0.001
    bpy.ops.object.modifier_apply(modifier="Shrinkwrap")

    # --- SOLIDIFY FOR DEPTH ---
    solidify = pattern_obj.modifiers.new(name="Solidify", type='SOLIDIFY')
    solidify.thickness = 0.5
    bpy.ops.object.modifier_apply(modifier="Solidify")

    # --- BOOLEAN DIFFERENCE ---
    bool_mod = stl_obj.modifiers.new(name="Boolean", type='BOOLEAN')
    bool_mod.operation = 'DIFFERENCE'
    bool_mod.object = pattern_obj
    bpy.context.view_layer.objects.active = stl_obj
    bpy.ops.object.modifier_apply(modifier="Boolean")

    # Optional cleanup
    bpy.data.objects.remove(pattern_obj, do_unlink=True)

    # --- EXPORT FINAL STL ---
    bpy.ops.export_mesh.stl(filepath=output_path)

    if args.verbose:
        print(f"Engraved STL saved to {output_path}")

# --- ENTRY POINT ---
if __name__ == "__main__":
    main()