Load BIM-VFI Model

Every VFI model in the Tween pack gets its own loader node, and this one loads the BIM-VFI checkpoint - the pack's best general-purpose frame interpolator. In the graph it sits at the head of a chain: Load BIM-VFI Model → BIM-VFI Interpolate → save. It's a thin node, but it packs three knobs that quietly matter more than you'd expect from a loader.

What it does. On first run it downloads the bim_vfi.pth checkpoint to ComfyUI/models/bim-vfi/ (it's a Google Drive download, so be patient on first use - the node is not frozen, it's fetching a few hundred MB). It outputs a single model object that wires straight into any BIM-VFI Interpolate or Segment Interpolate node's model input.

The inputs that matter:

• model_path - the checkpoint dropdown, defaulting to bim_vfi.pth. If you drop other checkpoints in models/bim-vfi/ they show up here.
• auto_pyr_level (on by default) - BIM-VFI processes frames in a coarse-to-fine pyramid, and this picks the level using the official policy: 5 below 1080p, 6 at 1080p, 7 at 4K. Leave it on. It's "smart defaults you don't have to think about" in the good sense.
• pyr_level - the manual pyramid override (3–7), only used when auto_pyr_level is off. More levels means it can capture larger motion but runs slower. You almost never need this.
• artifact_safe_mode (optional, off by default) - the interesting one. BIM-VFI has a known failure mode on blurry or large-motion shots where badly misaligned optical flow produces wrong-edge/halo artifacts around moving objects. This toggle disables the RGB refinement residual, which the official maintainer recommended as the workaround. Keep it off for normal footage (it can cost detail on easy shots) and flip it on selectively when you see halos.

How to install it. Install the pack itself - search "Tween" in ComfyUI Manager, or:

cd ComfyUI/custom_nodes
git clone https://github.com/Ethanfel/ComfyUI-Tween
pip install -r requirements.txt

Restart ComfyUI, add the node, and the checkpoint auto-downloads on the first execution of this loader. No separate model-hunting step, which is nicer than most VFI setups.

Gotchas. If the loader errors on first use, it's almost always the Google Drive fetch - check the console log and retry, or download bim_vfi.pth manually into models/bim-vfi/. And a licensing note worth having in your head: BIM-VFI is research/education-only. Commercial use requires permission from the KAIST lab, so if this feeds a product, use the Apache-2.0 models in the pack (EMA, SGM, GIMM, LDF) instead. The loader doesn't enforce this for you - that's between you and the license.