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Complete SCAIL-2 ComfyUI Workflow Guide: Character Replacement, Animation & Long Video Setup

Step-by-step tutorial on running SCAIL-2 natively in ComfyUI — covering SAM3 object tracking, Replacement vs Animation modes, model directory setup, and long video segment extension.

By CGFlowStudio
•
2026-08-20

Complete SCAIL-2 ComfyUI Workflow Guide: Character Replacement, Animation & Long Video Setup

SCAIL-2 represents a giant leap forward in AI character motion control and video editing. Built as an end-to-end character animation architecture on top of Wan 2.1 (14B), SCAIL-2 allows creators to take a reference portrait image and drive it using any video clip.

Crucially, SCAIL-2 operates without intermediate openpose skeletons or DWPose keypoint extractors. Using native SAM3 tracking and direct feature conditioning, SCAIL-2 supports two primary production modes: In-Video Character Replacement (swapping an actor in a scene with your character) and Standalone Character Animation (making your reference character perform motion against a clean background).

With native support now available in ComfyUI, this guide walks you step-by-step through setting up models, choosing between Replacement and Animation modes, executing long video chunking subgraphs, and troubleshooting common issues.

1. Introduction & Key Advantages

Traditional AI character swap pipelines required chaining multiple separate tools: pose extractors, ControlNet nodes, face swappers, and inpainting masks. SCAIL-2 consolidates this into an integrated single-pass model.

💡
Why SCAIL-2 Outperforms Keypoint Pipelines: Keypoint models (like DWPose or OpenPose) lose subtle hand gestures, clothing physics, and head tilt nuances. SCAIL-2 conditions directly on raw video latents and SAM3 masks, capturing micro-movements, fabric flow, and lighting consistency seamlessly.

Core Highlights

  • No Pose Extraction Required: Direct latent video conditioning replaces skeleton pipelines.
  • Dual Mode Support: Seamless toggle between Character Replacement (replace_mode = true) and Character Animation (replace_mode = false).
  • SAM3 Object Tracking Integration: Uses SAM3 (sam3.1_multiplex) for automated subject segmentation in both reference images and driving videos.
  • Long Video Segment Extension: Built-in chunking pipeline (81-frame default segments) allowing unlimited video duration via sequential subgraphs.

2. Getting Started – Loading the Official Workflow

ComfyUI includes an official native template for SCAIL-2 Character Replacement.

1 Update ComfyUI

Update ComfyUI to the latest release to ensure native nodes (WanSCAILToVideo, SCAIL2ColoredMask, SAM3Segment) are installed.

2 Open Template Library

Click Templates in the ComfyUI top menu and search for SCAIL-2 Character Replacement.

3 Examine Subgraph Architecture

The template contains two main visual sections: the **Base Subgraph** (renders the initial 81-frame segment) and **Extend Subgraphs** (chains subsequent segments for long videos).

3. How the Long Video Chunking Workflow Works

SCAIL-2 renders video in temporal chunks (default 81 frames per segment with an overlapping temporal boundary) to stay within VRAM bounds.

Long Video Segment Chaining Flow
Segment 0 (Base)
Base Subgraph

Renders Frames 0–80 using driving video & reference image.

Segment 1 (Extend)
Extend Subgraph 1

Takes final frames of Segment 0 as temporal overlap to render Frames 81–160.

Segment N (Extend)
Extend Subgraph N

Chains additional segments until full driving video length is rendered.

Manual Execution Note: In the default native workflow, each Extend segment subgraph must be queued manually after the preceding segment finishes rendering, ensuring strict memory release between chunks.

4. Two Operating Modes Explained

SCAIL-2 supports two primary production modes dictated by the replace_mode parameter and background mask color settings:

Mode 1 (Default) replace_mode = true

In-Video Character Replacement

Replaces the tracked actor inside the original video with your reference character while preserving the original background, lighting, and environmental interaction.

Mask Background Color: WHITE (#FFFFFF)
Mode 2 replace_mode = false

Standalone Character Animation

Extracts the performance motion from the driving video and applies it to your reference character against a generated or prompt-defined backdrop.

Mask Background Color: BLACK (#000000)

5. Model Installation & Directory Structure

Place all required SCAIL-2 checkpoints, text encoders, VAEs, and SAM3 tracking weights into the corresponding ComfyUI subdirectories:

📂 SCAIL-2 Model Component Directory Structure ComfyUI/models/
📂 ComfyUI/models/
📁 diffusion_models/
📄 wan2.1_14B_SCAIL_2_fp16.safetensors (Core SCAIL-2 DiT Model)
📁 text_encoders/
📄 umt5_xxl_fp8_e4m3fn_scaled.safetensors
📁 clip_vision/
📄 clip_vision_h.safetensors (Reference Character Feature Extractor)
📁 vae/
📄 Wan2_1_VAE_bf16.safetensors
📁 loras/
📄 wan2.1_SCAIL_2_DPO_lora_bf16.safetensors
📄 lightx2v_I2V_turbo_lora.safetensors (Optional 4-step acceleration)
📁 checkpoints/ (or sam3/)
📄 sam3.1_multiplex_fp16.safetensors (SAM3 Object Tracker)

6. Step-by-Step Execution Guide

Step 1: Input Preparation & SAM3 Tracking Setup

  1. Load Reference Image: Load your character portrait into the Load Image node. Set sam3_image_object text field to describe your subject (e.g. "woman, jacket").
  2. Load Driving Video: Load your target motion video. Set sam3_video_object to identify the person being tracked in the video (e.g. "man running").
  3. Verify Mask Preview: Inspect the SAM3 mask preview node to ensure the subject is cleanly segmented without background bleeding.

Step 2: Configure Shared Parameters

Set identical parameters across both Base and Extend subgraphs:

Parameter Configuration Reference

width / height: Must be divisible by 16 (e.g. 832 x 480 or 1024 x 576).
replace_mode: Set to true for character swap; false for animation.
frame_count: Set to 81 (standard segment length).
pose_strength: Recommended 1.0 for tight motion adherence.

Step 3: Run Base Subgraph (Segment 0)

Click Queue Prompt to render the first 81 frames of your video segment. ComfyUI will execute SAM3 tracking, encode latent conditioning, run WanSCAILToVideo, and decode Segment 0.

Step 4: Extending for Long Videos (Segments 1+)

For videos longer than 81 frames:

  1. Locate Extend Subgraph: Find the Extend Subgraph 1 node group on your canvas.
  2. Verify Connections: Ensure latent and mask outputs from Segment 0 feed into previous_latent and previous_mask input sockets of Segment 1.
  3. Set Segment Index: Set segment_index = 1.
  4. Queue Segment 1: Trigger Queue Prompt for Segment 1 rendering.
  5. Repeat for Subgraph N: Duplicate Extend subgraphs and increment segment_index for additional video length.

7. Key Parameters Reference Table

Parameter Name Recommended Value Functional Purpose
replace_mode true (Swap) / false (Anim) Toggles between in-video character replacement and standalone character performance.
sam3_image_object Text string (e.g. "girl") SAM3 text prompt for segmenting the reference character portrait.
sam3_video_object Text string (e.g. "man" ) SAM3 text prompt for tracking the actor in the driving video.
segment_index 0 (Base), 1, 2… (Extend) Temporal chunk index for long video generation.
pose_strength 0.8 – 1.0 Controls how strictly motion follows the driving video trajectory.
frame_count 81 (Default) Number of frames rendered per segment block.

8. Troubleshooting & Common Pitfalls

⚠️ Mismatched Mask Background Color

If using Replacement Mode (replace_mode = true), background mask color in SCAIL2ColoredMask must be White. If using Animation Mode (replace_mode = false), background mask must be Black. Mismatched colors cause severe background tearing.

📐 Aspect Ratio Discrepancies

Ensure the output width/height matches the aspect ratio of your driving video. If driving video is 16:9 widescreen, set canvas resolution to 832x480 or 1024x576 to avoid temporal distortion.

💾 VRAM Optimization (16GB GPUs)

If encountering Out-of-Memory crashes on 16GB VRAM GPUs, load quantized FP8 or GGUF versions of wan2.1_14B_SCAIL_2 and enable CPU offloading for UMT5 text encoding.

9. Conclusion & Next Steps

SCAIL-2 delivers unparalleled AI character replacement and motion animation inside ComfyUI without complex openpose intermediate nodes. By mastering SAM3 tracking inputs, selecting the correct replace_mode, and chaining Extend subgraphs, you can transform static character artwork into long, cinematic motion sequences.

Next Steps to Explore

  • Experiment with Animation Mode (replace_mode = false) to place reference characters in brand-new environments.
  • Combine SCAIL-2 with ControlNet or LightX2V Turbo LoRA for accelerated preview iterations.
  • Check out related tutorials on our ComfyHub Tutorials Directory.