gig-line/Tools/gen/generate_facade_textures.py

#!/usr/bin/env python3
"""Generate the facade texture maps the demo materials sample.

The materials started as procedural graphs only (noise + coursing), which reads
as tinted stone but has no grain. These maps add the grain: an ashlar stone
course pattern, a rendered stucco tooth, asphalt aggregate and concrete pores,
each as base colour plus a roughness map so the specular breaks up.

Standard library only — the PNG encoder is the same pure-zlib writer used for the
MPFB skin, so this runs on the host without numpy or Pillow.

    python3 Tools/gen/generate_facade_textures.py                 # write to /tmp/gigline/textures
    python3 Tools/gen/generate_facade_textures.py --size 1024
    python3 Tools/gen/generate_facade_textures.py --out Art/blender/textures

Output names match the Unreal import destination `/Game/Hollywood/Textures`:

    T_StoneAshlar_BC.png   T_StoneAshlar_R.png
    T_Stucco_BC.png        T_Stucco_R.png
    T_Asphalt_BC.png       T_Asphalt_R.png
    T_Concrete_BC.png      T_Concrete_R.png

Determinism: every pattern is a deterministic hash of the pixel coordinate, so a
re-run reproduces the same files byte for byte (no RNG state, no seam drift).
"""

from __future__ import annotations

import argparse
import math
import os
import struct
import zlib

# --- PNG -------------------------------------------------------------------


def write_png(path, width, height, rgb_rows):
    """Write 8-bit RGB rows (bytes) to a PNG. `rgb_rows` is one bytes per row."""
    raw = bytearray()
    for y in range(height):
        raw.append(0)  # filter type 0
        raw += rgb_rows[y]

    def chunk(tag, data):
        c = struct.pack(">I", len(data)) + tag + data
        c += struct.pack(">I", zlib.crc32(tag + data) & 0xFFFFFFFF)
        return c

    ihdr = struct.pack(">IIBBBBB", width, height, 8, 2, 0, 0, 0)  # colour type 2 = RGB
    png = b"\x89PNG\r\n\x1a\n" + chunk(b"IHDR", ihdr)
    png += chunk(b"IDAT", zlib.compress(bytes(raw), 6)) + chunk(b"IEND", b"")
    os.makedirs(os.path.dirname(os.path.abspath(path)), exist_ok=True)
    with open(path, "wb") as handle:
        handle.write(png)
    return path


# --- deterministic value noise --------------------------------------------


def _hash2(x, y, seed=0):
    """Deterministic 0..1 hash of an integer cell. No RNG, fully reproducible."""
    n = (x * 374761393 + y * 668265263 + seed * 1442695040888963407) & 0xFFFFFFFF
    n = (n ^ (n >> 13)) * 1274126177 & 0xFFFFFFFF
    return ((n ^ (n >> 16)) & 0xFFFF) / 65535.0


def value_noise(x, y, seed=0):
    """Smooth bilinear value noise at continuous (x, y) in cell units."""
    xi, yi = math.floor(x), math.floor(y)
    fx, fy = x - xi, y - yi
    # smoothstep weights so cells blend without visible lattice lines
    sx = fx * fx * (3.0 - 2.0 * fx)
    sy = fy * fy * (3.0 - 2.0 * fy)
    n00 = _hash2(xi, yi, seed)
    n10 = _hash2(xi + 1, yi, seed)
    n01 = _hash2(xi, yi + 1, seed)
    n11 = _hash2(xi + 1, yi + 1, seed)
    return (n00 * (1 - sx) + n10 * sx) * (1 - sy) + (n01 * (1 - sx) + n11 * sx) * sy


def fractal(x, y, octaves=4, seed=0):
    """Fractal sum of value noise, normalised to 0..1."""
    total, amp, freq, norm = 0.0, 1.0, 1.0, 0.0
    for _ in range(octaves):
        total += value_noise(x * freq, y * freq, seed) * amp
        norm += amp
        amp *= 0.5
        freq *= 2.0
    return total / norm


def clamp8(value):
    return max(0, min(255, int(value * 255.0 + 0.5)))


# --- patterns --------------------------------------------------------------
# Each returns (base_rgb_function, roughness_function) over u, v in 0..1.


def stone_ashlar(courses=8, per_course=4):
    """Coursed ashlar: horizontal beds, staggered vertical joints, stone grain."""
    course_h = 1.0 / courses

    def block_uv(u, v):
        row = int(v / course_h)
        shift = 0.5 * (row % 2) / per_course  # stagger alternate courses
        col = int(((u + shift) % 1.0) * per_course)
        return row, col, (v % course_h) / course_h, ((u + shift) % 1.0) * per_course - col

    def base(u, v, px, py):
        row, col, fj, fi = block_uv(u, v)
        tone = 0.62 + 0.10 * _hash2(row, col, 11)          # each block a little different
        grain = 0.06 * (fractal(px * 0.15, py * 0.15, 5, 3) - 0.5) * 2.0
        # joint: a dark band along the bed and the head of each block
        joint = 0.0
        if fj < 0.055 or fi < 0.055:
            joint = -0.22
        value = tone + grain + joint
        return (value * 1.02, value, value * 0.94)          # faintly warm stone

    def rough(u, v, px, py):
        row, col, fj, fi = block_uv(u, v)
        base_r = 0.66 + 0.10 * _hash2(row, col, 29)
        if fj < 0.055 or fi < 0.055:
            base_r = 0.86                                     # joints are matte
        return base_r + 0.06 * fractal(px * 0.2, py * 0.2, 3, 7)

    return base, rough


def stucco():
    def base(u, v, px, py):
        blot = fractal(px * 0.03, py * 0.03, 4, 21)
        tooth = fractal(px * 0.9, py * 0.9, 3, 22)
        value = 0.58 + 0.12 * (blot - 0.5) + 0.05 * (tooth - 0.5)
        return (value * 1.03, value, value * 0.96)

    def rough(u, v, px, py):
        return 0.74 + 0.18 * fractal(px * 0.06, py * 0.06, 3, 31)

    return base, rough


def asphalt():
    def base(u, v, px, py):
        agg = fractal(px * 1.4, py * 1.4, 3, 41)              # fine aggregate
        patch = fractal(px * 0.02, py * 0.02, 3, 42)           # repair patches
        value = 0.055 + 0.05 * (patch - 0.5) + 0.06 * (agg - 0.5)
        return (value, value, value * 1.05)                    # cool bitumen

    def rough(u, v, px, py):
        return 0.90 + 0.08 * fractal(px * 0.5, py * 0.5, 2, 43)

    return base, rough


def concrete():
    def base(u, v, px, py):
        pores = fractal(px * 0.8, py * 0.8, 3, 51)
        tone = fractal(px * 0.04, py * 0.04, 4, 52)
        value = 0.50 + 0.10 * (tone - 0.5) + 0.05 * (pores - 0.5)
        return (value * 1.01, value, value * 0.97)

    def rough(u, v, px, py):
        return 0.84 + 0.10 * fractal(px * 0.15, py * 0.15, 3, 53)

    return base, rough


TEXTURES = {
    "T_StoneAshlar": stone_ashlar(),
    "T_Stucco": stucco(),
    "T_Asphalt": asphalt(),
    "T_Concrete": concrete(),
}


def render(name, pattern, size):
    """Render one texture; returns {suffix: path} for _BC and _R."""
    base_fn, rough_fn = pattern
    paths = {}
    for suffix, fn in (("BC", base_fn), ("R", rough_fn)):
        # Wrap in a function so the inner loop stays tight.
        rows = []
        for y in range(size):
            v = y / size
            row = bytearray()
            for x in range(size):
                u = x / size
                value = fn(u, v, x / size * size / 64.0, y / size * size / 64.0)
                if isinstance(value, tuple):
                    row += bytes((clamp8(value[0]), clamp8(value[1]), clamp8(value[2])))
                else:
                    grey = clamp8(value)
                    row += bytes((grey, grey, grey))
            rows.append(bytes(row))
        path = os.path.join(OUT_DIR, f"{name}_{suffix}.png")
        write_png(path, size, size, rows)
        paths[suffix] = path
    return paths


def main(argv=None) -> int:
    global OUT_DIR
    ap = argparse.ArgumentParser(description=__doc__,
                                 formatter_class=argparse.RawDescriptionHelpFormatter)
    ap.add_argument("--out", default="/tmp/gigline/textures",
                    help="output directory (default /tmp/gigline/textures)")
    ap.add_argument("--size", type=int, default=512, help="edge length in pixels")
    args = ap.parse_args(argv)
    OUT_DIR = args.out

    print(f"writing {len(TEXTURES) * 2} maps at {args.size}² to {OUT_DIR}")
    for name, pattern in TEXTURES.items():
        paths = render(name, pattern, args.size)
        for suffix, path in paths.items():
            print(f"  {os.path.basename(path):28} {os.path.getsize(path):>8} bytes")
    return 0


OUT_DIR = "/tmp/gigline/textures"

if __name__ == "__main__":
    raise SystemExit(main())