🤖 AI Summary
This work addresses the challenge of generating diverse and physically plausible humanoid motions with existing physics-based control methods—such as VAEs or AMP—which often suffer from information loss or mode collapse. The authors propose a two-stage framework: first, a high-fidelity motion-tracking controller is trained; then, its policy is distilled into a spherical latent action space, augmented with a discriminator and local semantic consistency constraints to structure the latent space. This approach uniquely integrates spherical latent representations, policy distillation, and adversarial discrimination, enabling stable, semantically meaningful random sampling while preserving fine-grained motion details. Evaluated on a newly collected two-hour martial arts motion capture dataset, the method generates realistic, physically valid, and morphology-agnostic combat behaviors using only simple rule-based rewards.
📝 Abstract
Learning motion priors for physics-based humanoid control is an active research topic. Existing approaches mainly include variational autoencoders (VAE) and adversarial motion priors (AMP). VAE introduces information loss, and random latent sampling may sometimes produce invalid behaviors. AMP suffers from mode collapse and struggles to capture diverse motion skills. We present the Spherical Latent Motion Prior (SLMP), a two-stage method for learning motion priors. In the first stage, we train a high-quality motion tracking controller. In the second stage, we distill the tracking controller into a spherical latent space. A combination of distillation, a discriminator, and a discriminator-guided local semantic consistency constraint shapes a structured latent action space, allowing stable random sampling without information loss. To evaluate SLMP, we collect a two-hour human combat motion capture dataset and show that SLMP preserves fine motion detail without information loss, and random sampling yields semantically valid and stable behaviors. When applied to a two-agent physics-based combat task, SLMP produces human-like and physically plausible combat behaviors only using simple rule-based rewards. Furthermore, SLMP generalizes across different humanoid robot morphologies, demonstrating its transferability beyond a single simulated avatar.