blender_render.py

"""Drive Blender to photorealistically render the generated DrivAer car.

Generates the part-labelled car mesh, dumps it to an npz, and runs Blender
(Cycles, GPU) headless to produce a studio render of the REAL geometry -
metallic paint, glass, chrome rims, rubber tyres, emissive lamps.

This is the photoreal render of the actual 3D model (not a diffusion image),
so it matches the car you can rotate / simulate / inspect.
"""
from __future__ import annotations

import glob
import os
import subprocess
import tempfile
from pathlib import Path
from typing import Optional

import numpy as np

HERE = Path(__file__).parent
SCRIPT = HERE / "render_car_blender.py"
_BLENDER = None


def find_blender() -> Optional[str]:
    global _BLENDER
    if _BLENDER:
        return _BLENDER
    cands = []
    import shutil
    p = shutil.which("blender")
    if p:
        cands.append(p)
    cands += sorted(glob.glob(
        r"C:\Program Files\Blender Foundation\Blender *\blender.exe"), reverse=True)
    cands += sorted(glob.glob(
        r"C:\Program Files\Blender Foundation\*\blender.exe"), reverse=True)
    for c in cands:
        if c and os.path.exists(c):
            _BLENDER = c
            return c
    return None


def available() -> bool:
    return find_blender() is not None


def _hex(color) -> str:
    import vehicle_realgen as G
    rgb = G.resolve_color(color) if isinstance(color, str) else color
    if rgb is None:
        rgb = (0.69, 0.71, 0.74)
    return "".join(f"{int(max(0,min(1,c))*255):02x}" for c in rgb[:3])


def render(length_mm=4700.0, width_mm=1900.0, height_mm=1450.0,
           roof=0.0, nose=0.0, rake=0.0, target_cd=None,
           color="silver", out_path: Optional[str] = None,
           timeout=600, mode="photoreal") -> Optional[str]:
    blender = find_blender()
    if blender is None:
        return None
    import drivaer_meshgen as MG
    d = MG.generate(length_mm=length_mm, width_mm=width_mm, height_mm=height_mm,
                    roof=roof, nose=nose, rake=rake, target_cd=target_cd)
    if d is None:
        return None
    tmp = Path(tempfile.gettempdir()) / "chatcad_car_mesh.npz"
    np.savez(tmp, verts=d["verts"].astype(np.float32),
             faces=np.asarray(d["faces"], np.int32),
             region=np.asarray(d["region"], np.int32))
    out_path = out_path or str(HERE / "output" / "blender_car.png")
    Path(out_path).parent.mkdir(parents=True, exist_ok=True)
    cmd = [blender, "-b", "-noaudio", "-P", str(SCRIPT), "--",
           str(tmp), out_path, _hex(color), mode]
    try:
        subprocess.run(cmd, timeout=timeout, capture_output=True)
    except Exception:
        return None
    return out_path if os.path.exists(out_path) else None


if __name__ == "__main__":
    print("blender:", find_blender())
    import time
    t = time.time()
    p = render(length_mm=4600, height_mm=1350, roof=0.6, nose=0.4,
               target_cd=0.24, color="red")
    print("rendered:", p, "in %.1fs" % (time.time() - t))