io_export_paper_model.py

# -*- coding: utf-8 -*-
# This script is Free software. Please share and reuse.
# ♡2010-2020 Adam Dominec <adominec@gmail.com>

## Code structure
# This file consists of several components, in this order:
# * Unfolding and baking
# * Export (SVG or PDF)
# * User interface
# During the unfold process, the mesh is mirrored into a 2D structure: UVFace, UVEdge, UVVertex.

bl_info = {
    "name": "Export Paper Model",
    "author": "Addam Dominec",
    "version": (1, 2),
    "blender": (2, 83, 0),
    "location": "File > Export > Paper Model",
    "warning": "",
    "description": "Export printable net of the active mesh",
    "doc_url": "{BLENDER_MANUAL_URL}/addons/import_export/paper_model.html",
    "category": "Import-Export",
}

# Task: split into four files (SVG and PDF separately)
# * does any portion of baking belong into the export module?
# * sketch out the code for GCODE and two-sided export

# TODO:
# QuickSweepline is very much broken -- it throws GeometryError for all nets > ~15 faces
# rotate islands to minimize area -- and change that only if necessary to fill the page size

# check conflicts in island naming and either:
# * append a number to the conflicting names or
# * enumerate faces uniquely within all islands of the same name (requires a check that both label and abbr. equals)

import bpy
import bl_operators
import bmesh
import mathutils as M
from re import compile as re_compile
from itertools import chain, repeat, product, combinations
from math import pi, ceil, asin, atan2
import os.path as os_path

default_priority_effect = {
    'CONVEX': 0.5,
    'CONCAVE': 1,
    'LENGTH': -0.05
}

global_paper_sizes = [
    ('USER', "User defined", "User defined paper size"),
    ('A4', "A4", "International standard paper size"),
    ('A3', "A3", "International standard paper size"),
    ('US_LETTER', "Letter", "North American paper size"),
    ('US_LEGAL', "Legal", "North American paper size")
]


def first_letters(text):
    """Iterator over the first letter of each word"""
    for match in first_letters.pattern.finditer(text):
        yield text[match.start()]
first_letters.pattern = re_compile(r"((?<!\w)\w)|\d")


def is_upsidedown_wrong(name):
    """Tell if the string would get a different meaning if written upside down"""
    chars = set(name)
    mistakable = set("69NZMWpbqd")
    rotatable = set("80oOxXIl").union(mistakable)
    return chars.issubset(rotatable) and not chars.isdisjoint(mistakable)


def pairs(sequence):
    """Generate consecutive pairs throughout the given sequence; at last, it gives elements last, first."""
    i = iter(sequence)
    previous = first = next(i)
    for this in i:
        yield previous, this
        previous = this
    yield this, first


def fitting_matrix(v1, v2):
    """Get a matrix that rotates v1 to the same direction as v2"""
    return (1 / v1.length_squared) * M.Matrix((
        (v1.x*v2.x + v1.y*v2.y, v1.y*v2.x - v1.x*v2.y),
        (v1.x*v2.y - v1.y*v2.x, v1.x*v2.x + v1.y*v2.y)))


def z_up_matrix(n):
    """Get a rotation matrix that aligns given vector upwards."""
    b = n.xy.length
    s = n.length
    if b > 0:
        return M.Matrix((
            (n.x*n.z/(b*s), n.y*n.z/(b*s), -b/s),
            (-n.y/b, n.x/b, 0),
            (0, 0, 0)
        ))
    else:
        # no need for rotation
        return M.Matrix((
            (1, 0, 0),
            (0, (-1 if n.z < 0 else 1), 0),
            (0, 0, 0)
        ))


def cage_fit(points, aspect):
    """Find rotation for a minimum bounding box with a given aspect ratio
    returns a tuple: rotation angle, box height"""
    def guesses(polygon):
        """Yield all tentative extrema of the bounding box height wrt. polygon rotation"""
        for a, b in pairs(polygon):
            if a == b:
                continue
            direction = (b - a).normalized()
            sinx, cosx = -direction.y, direction.x
            rot = M.Matrix(((cosx, -sinx), (sinx, cosx)))
            rot_polygon = [rot @ p for p in polygon]
            left, right = [fn(rot_polygon, key=lambda p: p.to_tuple()) for fn in (min, max)]
            bottom, top = [fn(rot_polygon, key=lambda p: p.yx.to_tuple()) for fn in (min, max)]
            horz, vert = right - left, top - bottom
            # solve (rot * a).y == (rot * b).y
            yield max(aspect * horz.x, vert.y), sinx, cosx
            # solve (rot * a).x == (rot * b).x
            yield max(horz.x, aspect * vert.y), -cosx, sinx
            # solve aspect * (rot * (right - left)).x == (rot * (top - bottom)).y
            # using substitution t = tan(rot / 2)
            q = aspect * horz.x - vert.y
            r = vert.x + aspect * horz.y
            t = ((r**2 + q**2)**0.5 - r) / q if q != 0 else 0
            t = -1 / t if abs(t) > 1 else t  # pick the positive solution
            siny, cosy = 2 * t / (1 + t**2), (1 - t**2) / (1 + t**2)
            rot = M.Matrix(((cosy, -siny), (siny, cosy)))
            for p in rot_polygon:
                p[:] = rot @ p  # note: this also modifies left, right, bottom, top
            if left.x < right.x and bottom.y < top.y and all(left.x <= p.x <= right.x and bottom.y <= p.y <= top.y for p in rot_polygon):
                yield max(aspect * (right - left).x, (top - bottom).y), sinx*cosy + cosx*siny, cosx*cosy - sinx*siny
    polygon = [points[i] for i in M.geometry.convex_hull_2d(points)]
    height, sinx, cosx = min(guesses(polygon))
    return atan2(sinx, cosx), height


def create_blank_image(image_name, dimensions, alpha=1):
    """Create a new image and assign white color to all its pixels"""
    image_name = image_name[:64]
    width, height = int(dimensions.x), int(dimensions.y)
    image = bpy.data.images.new(image_name, width, height, alpha=True)
    if image.users > 0:
        raise UnfoldError(
            "There is something wrong with the material of the model. "
            "Please report this on the BlenderArtists forum. Export failed.")
    image.pixels = [1, 1, 1, alpha] * (width * height)
    image.file_format = 'PNG'
    return image


def store_rna_properties(*datablocks):
    return [{prop.identifier: getattr(data, prop.identifier) for prop in data.rna_type.properties if not prop.is_readonly} for data in datablocks]


def apply_rna_properties(memory, *datablocks):
    for recall, data in zip(memory, datablocks):
        for key, value in recall.items():
            setattr(data, key, value)


class UnfoldError(ValueError):
    def mesh_select(self):
        if len(self.args) > 1:
            elems, bm = self.args[1:3]
            bpy.context.tool_settings.mesh_select_mode = [bool(elems[key]) for key in ("verts", "edges", "faces")]
            for elem in chain(bm.verts, bm.edges, bm.faces):
                elem.select = False
            for elem in chain(*elems.values()):
                elem.select_set(True)
            bmesh.update_edit_mesh(bpy.context.object.data, loop_triangles=False, destructive=False)


class Unfolder:
    def __init__(self, ob):
        self.do_create_uvmap = False
        bm = bmesh.from_edit_mesh(ob.data)
        self.mesh = Mesh(bm, ob.matrix_world)
        self.mesh.check_correct()

    def __del__(self):
        if not self.do_create_uvmap:
            self.mesh.delete_uvmap()

    def prepare(self, cage_size=None, priority_effect=default_priority_effect, scale=1, limit_by_page=False):
        """Create the islands of the net"""
        self.mesh.generate_cuts(cage_size / scale if limit_by_page and cage_size else None, priority_effect)
        self.mesh.finalize_islands(cage_size or M.Vector((1, 1)))
        self.mesh.enumerate_islands()
        self.mesh.save_uv()