Compress baked PNGs and tighten XPbr shadows with URP quality tweaks.

Add png_compress to the model pipeline and update TownSquare lighting plus MaleExplorer/plaza textures.

Co-authored-by: Cursor <cursoragent@cursor.com>

Tools/model_tools/README.md

@@ -9,6 +9,7 @@
   -> model_translator：打包为 XPbr 两张图 + .mat/.meta
        _base.png  RGB=Albedo  A=AO/透明
        _mix.png   RG=球面法线  B=Metallic  A=Roughness
+       写出时 PNG 无损压缩（体积更小，像素不变）
 ```
 
 ## 环境

Tools/model_tools/bl_bake.py

@@ -7,6 +7,7 @@ import os
 import sys
 
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+from png_compress import compress_png, prepare_blender_png
 
 DEFAULT_RAY_PCT = 0.02   # 测量失败时回退：低模包围盒对角线 * 2%
 RAY_SAFETY = 1.5        # 自适应射线安全系数（分离 P99 × 此值）
@@ -199,8 +200,10 @@ def _bake_pass(low, high, target_node, name, bake_type, size, colorspace,
     path = os.path.abspath(os.path.join(outdir, "%s_%s.png" % (stem, name)))
     img.filepath_raw = path
     img.file_format = 'PNG'
+    prepare_blender_png(100)
     img.save()
     bpy.data.images.remove(img)
+    compress_png(path)
     return os.path.basename(path)
 
 

Tools/model_tools/bl_convert.py

@@ -9,6 +9,7 @@ import numpy as np
 
 # blender --python 不会把脚本目录加入 sys.path，手动加入以复用 unity_assets（纯 stdlib）
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+from png_compress import compress_png, prepare_blender_png
 from unity_assets import safe_name
 
 AO_NAME_RE = re.compile(r"(ao|occlusion|ambient)", re.I)
@@ -269,8 +270,10 @@ def _save_png(path, rgba):
     img.filepath_raw = path
     img.file_format = 'PNG'
     img.alpha_mode = 'CHANNEL_PACKED'
+    prepare_blender_png(100)
     img.save()
     bpy.data.images.remove(img)
+    compress_png(path)
 
 
 def _convert_material(mat, model_name, outdir, max_size, used_snames, src_dir):

Tools/model_tools/model_bake.py

@@ -8,6 +8,7 @@ import os
 from bl_bake import output_stem
 from bl_decimate import model_format
 from mt_run import HERE, find_blender, run_blender_script
+from png_compress import compress_pngs
 
 
 def main():
@@ -38,6 +39,9 @@ def main():
                            [args.high, args.low, outdir, str(args.size),
                             ray, str(args.samples)],
                            blender_args=("-t", "1"))
+    compress_pngs(
+        os.path.join(outdir, fname) for fname in (s.get("outputs") or {}).values()
+    )
     print("== %s（高 %d 面 / 低 %d 面，射线距离 %.4f）-> %s" %
           (s["stem"], s["high_tris"], s["low_tris"], s["ray_distance"], outdir))
     for name, fname in s["outputs"].items():

Tools/model_tools/model_lowpoly_bake.py

@@ -28,6 +28,7 @@ if str(_HERE) not in sys.path:
 from bl_bake import output_stem  # noqa: E402
 from bl_decimate import model_format  # noqa: E402
 from mt_run import find_blender, run_blender_script  # noqa: E402
+from png_compress import compress_pngs  # noqa: E402
 
 
 def _now_iso() -> str:
@@ -211,6 +212,9 @@ def run_pipeline(
         ],
         blender_args=("-t", "1"),
     )
+    compress_pngs(
+        str(bake_dir / fname) for fname in (bake.get("outputs") or {}).values()
+    )
 
     xpbr_dir = None
     xpbr_summary = None

Tools/model_tools/model_translator.py

@@ -8,6 +8,7 @@ import sys
 
 import unity_assets as ua
 from mt_run import HERE, find_blender, run_blender_script
+from png_compress import compress_dir_pngs
 
 
 def write_unity_assets(outdir, summary, max_size):
@@ -79,6 +80,7 @@ def translate_fbx(src, outdir, max_size=2048, blender=None):
     summary = run_blender_script(
         blender_exe, "bl_convert.py", [src, outdir, str(max_size)]
     )
+    compress_dir_pngs(outdir, suffixes=("_base.png", "_mix.png"))
     unity = write_unity_assets(outdir, summary, max_size)
     return {**summary, "unity": unity}
 

Tools/model_tools/png_compress.py

@@ -0,0 +1,139 @@
+"""Lossless PNG size reduction for bake outputs.
+
+Blender's default PNG compression is low (~15/100). Final _base/_mix (and
+bake maps) are rewritten with zlib level 9. Pillow `optimize=True` is used
+when available (system Python); Blender's interpreter falls back to IDAT
+recompress via stdlib only. Pixels are unchanged.
+"""
+from __future__ import annotations
+
+import os
+import struct
+import zlib
+from typing import Dict, Iterable, List, Optional
+
+PNG_SIG = b"\x89PNG\r\n\x1a\n"
+
+
+def prepare_blender_png(compression: int = 100) -> None:
+    """Blender Image.save() uses scene render PNG compression (0-100)."""
+    import bpy
+
+    settings = bpy.context.scene.render.image_settings
+    settings.file_format = "PNG"
+    settings.color_depth = "8"
+    settings.compression = int(compression)
+
+
+def compress_png(path: str, level: int = 9) -> Dict[str, int]:
+    """Rewrite `path` in place. Returns {before, after} byte sizes."""
+    path = os.path.abspath(path)
+    before = os.path.getsize(path)
+    after = before
+    tmp = path + ".pngcompress.tmp"
+    try:
+        if _compress_with_pillow(path, tmp, level) or _compress_idat(path, tmp, level):
+            new_size = os.path.getsize(tmp)
+            if new_size < before:
+                os.replace(tmp, path)
+                after = new_size
+            elif os.path.isfile(tmp):
+                os.remove(tmp)
+    finally:
+        if os.path.isfile(tmp):
+            try:
+                os.remove(tmp)
+            except OSError:
+                pass
+    return {"before": before, "after": after}
+
+
+def compress_pngs(paths: Iterable[str], level: int = 9) -> List[Dict[str, object]]:
+    reports = []
+    for path in paths:
+        if not path or not os.path.isfile(path):
+            continue
+        if os.path.splitext(path)[1].lower() != ".png":
+            continue
+        sizes = compress_png(path, level=level)
+        reports.append({"path": os.path.abspath(path), **sizes})
+    return reports
+
+
+def compress_dir_pngs(directory: str, suffixes: Optional[Iterable[str]] = None) -> List[Dict[str, object]]:
+    """Compress PNGs in a directory. `suffixes` like ('_base.png', '_mix.png')."""
+    directory = os.path.abspath(directory)
+    names = sorted(os.listdir(directory)) if os.path.isdir(directory) else []
+    suffix_tuple = tuple(suffixes) if suffixes else None
+    paths = []
+    for name in names:
+        if not name.lower().endswith(".png"):
+            continue
+        if suffix_tuple and not name.endswith(suffix_tuple):
+            continue
+        paths.append(os.path.join(directory, name))
+    return compress_pngs(paths)
+
+
+def _compress_with_pillow(src: str, dst: str, level: int) -> bool:
+    try:
+        from PIL import Image
+    except ImportError:
+        return False
+    try:
+        with Image.open(src) as im:
+            im.load()
+            im.save(dst, format="PNG", optimize=True, compress_level=level)
+    except Exception:
+        return False
+    return os.path.isfile(dst)
+
+
+def _write_chunk(buf: bytearray, ctype: bytes, data: bytes) -> None:
+    buf.extend(struct.pack(">I", len(data)))
+    buf.extend(ctype)
+    buf.extend(data)
+    buf.extend(struct.pack(">I", zlib.crc32(ctype + data) & 0xFFFFFFFF))
+
+
+def _compress_idat(src: str, dst: str, level: int) -> bool:
+    with open(src, "rb") as f:
+        data = f.read()
+    if len(data) < 8 or data[:8] != PNG_SIG:
+        return False
+    pos = 8
+    before_idat: List[tuple] = []
+    after_idat: List[tuple] = []
+    idat_parts: List[bytes] = []
+    seen_idat = False
+    while pos + 12 <= len(data):
+        length = struct.unpack(">I", data[pos : pos + 4])[0]
+        ctype = data[pos + 4 : pos + 8]
+        end = pos + 8 + length
+        if end + 4 > len(data):
+            return False
+        cdata = data[pos + 8 : end]
+        pos = end + 4
+        if ctype == b"IDAT":
+            idat_parts.append(cdata)
+            seen_idat = True
+            continue
+        if seen_idat:
+            after_idat.append((ctype, cdata))
+        else:
+            before_idat.append((ctype, cdata))
+        if ctype == b"IEND":
+            break
+    if not idat_parts:
+        return False
+    raw = zlib.decompress(b"".join(idat_parts))
+    packed = zlib.compress(raw, level)
+    out = bytearray(PNG_SIG)
+    for ctype, cdata in before_idat:
+        _write_chunk(out, ctype, cdata)
+    _write_chunk(out, b"IDAT", packed)
+    for ctype, cdata in after_idat:
+        _write_chunk(out, ctype, cdata)
+    with open(dst, "wb") as f:
+        f.write(out)
+    return True

Tools/model_tools/tests/test_png_compress.py

@@ -0,0 +1,31 @@
+import os
+import sys
+import tempfile
+import unittest
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+from png_compress import compress_png
+
+
+class CompressPngTests(unittest.TestCase):
+    def test_pixels_unchanged_and_smaller(self):
+        from PIL import Image
+
+        w = h = 64
+        pixels = [(40, 80, 120, 255)] * (w * h)
+        with tempfile.TemporaryDirectory() as d:
+            path = os.path.join(d, "a.png")
+            im = Image.new("RGBA", (w, h))
+            im.putdata(pixels)
+            im.save(path, format="PNG", compress_level=0, optimize=False)
+            before = os.path.getsize(path)
+            src_bytes = list(Image.open(path).getdata())
+            sizes = compress_png(path)
+            after_im = Image.open(path)
+            self.assertEqual(list(after_im.getdata()), src_bytes)
+            self.assertLess(sizes["after"], before)
+            self.assertEqual(sizes["before"], before)
+
+
+if __name__ == "__main__":
+    unittest.main()