Mask2Real-WM: Segmentation Masks as a Sim-to-Real Bridge for Controllable Dexterous World Models

Learning action-conditioned world models for dexterous manipulation that are genuinely controllable requires capturing complex, high-dimensional hand kinematics from limited real-world data. We present Mask2Real-WM, a two-stage world model that improves controllability for dexterous hands under a limited real-data budget by decoupling pixel prediction into a dynamics model and a rendering model. The dynamics model predicts future segmentation masks from past masks and a high-dimensional action sequence. The rendering model converts the predicted masks into photorealistic RGB images. This design allows us to train the dynamics model on a large synthetic dataset spanning the full range of hand motions and interactions. We then fine-tune the dynamics model and train the rendering model on only 2.5 h of real demonstrations to obtain a controllable world model. We compare five models with matched training recipes on a 23-DoF robotic system, measuring per-DoF controllability both with random target commands and with sinusoidal per-DoF actuation, judged blind by human raters. The decoupled model achieves the strongest controllability, with further gains from simulation data. Beyond improved controllability, Mask2Real-WM produces sharper frames while maintaining comparable perceptual quality.