Running Blender on multiple GPUs on Modal.com

readme.md

1. Put example.blend file near blend.py
2. Run modal run blend.py

blend.py

from pathlib import Path
from typing import Dict
import modal
import modal.gpu

app = modal.App("blender")

rendering_image = (
    modal.Image.debian_slim(python_version="3.11")
    .apt_install("xorg", "libxkbcommon0", "ffmpeg")
    .pip_install("bpy==4.1.0")
)

def configure_rendering(ctx):
    # configure the rendering process
    ctx.scene.render.engine = "CYCLES"
    ctx.scene.render.resolution_x = 1920
    ctx.scene.render.resolution_y = 1080
    ctx.scene.render.resolution_percentage = 100
    ctx.scene.render.image_settings.file_format = 'PNG'
    ctx.scene.cycles.samples = 4096

    cycles = ctx.preferences.addons["cycles"]

    cycles.preferences.compute_device_type = "CUDA"
    ctx.scene.cycles.device = "GPU"
  
    # reload the devices to update the configuration
    cycles.preferences.get_devices()
    for device in cycles.preferences.devices:
        device.use = True

    # report rendering devices -- a nice snippet for debugging and ensuring the accelerators are being used
    for dev in cycles.preferences.devices:
        print(
            f"ID:{dev['id']} Name:{dev['name']} Type:{dev['type']} Use:{dev['use']}"
        )

@app.function(
    gpu=modal.gpu.L4(count=8),
    image=rendering_image,
)
def render(blend_file: bytes, frame_number: int = 0) -> bytes:
    """Renders the n-th frame of a Blender file as a PNG."""
    import bpy

    input_path = "/tmp/input.blend"
    output_path = f"/tmp/output-{frame_number}.png"

    # Blender requires input as a file.
    Path(input_path).write_bytes(blend_file)

    bpy.ops.wm.open_mainfile(filepath=input_path)
    bpy.context.scene.frame_set(frame_number)
    bpy.context.scene.render.filepath = output_path
    configure_rendering(bpy.context)
    bpy.ops.render.render(write_still=True)

    # Blender renders image outputs to a file as well.
    return Path(output_path).read_bytes()

@app.function(image=rendering_image)
def run(blend_bytes: bytes) -> bytes:
    output_directory = Path("/tmp") / "render"
    output_directory.mkdir(parents=True, exist_ok=True)
    args = [
        (blend_bytes, frame) for frame in range(1, 1, 1)
    ]
    images = list(render.starmap(args))
    return images[0]

@app.local_entrypoint()
def main():
    output_directory = Path("/tmp") / "render"
    output_directory.mkdir(parents=True, exist_ok=True)

    input_path = Path(__file__).parent / "example.blend"
    blend_bytes = input_path.read_bytes()

    video_bytes = run.remote(blend_bytes)
    video_path = Path(__file__).parent / "image.png"
    video_path.write_bytes(video_bytes)
    print("DONE!")