KAGE-Bench: Fast Known-Axis Visual Generalization Evaluation for Reinforcement Learning
This provides a systematic tool for researchers to analyze visual generalization failures in RL, though it is incremental as it builds on existing environments and methods.
The paper tackles the problem of evaluating visual generalization in reinforcement learning by introducing KAGE-Bench, a benchmark that isolates individual visual shifts, and finds that background and photometric shifts often cause complete failure in pixel-based agents while agent-appearance shifts are less harmful.
Pixel-based reinforcement learning agents often fail under purely visual distribution shift even when latent dynamics and rewards are unchanged, but existing benchmarks entangle multiple sources of shift and hinder systematic analysis. We introduce KAGE-Env, a JAX-native 2D platformer that factorizes the observation process into independently controllable visual axes while keeping the underlying control problem fixed. By construction, varying a visual axis affects performance only through the induced state-conditional action distribution of a pixel policy, providing a clean abstraction for visual generalization. Building on this environment, we define KAGE-Bench, a benchmark of six known-axis suites comprising 34 train-evaluation configuration pairs that isolate individual visual shifts. Using a standard PPO-CNN baseline, we observe strong axis-dependent failures, with background and photometric shifts often collapsing success, while agent-appearance shifts are comparatively benign. Several shifts preserve forward motion while breaking task completion, showing that return alone can obscure generalization failures. Finally, the fully vectorized JAX implementation enables up to 33M environment steps per second on a single GPU, enabling fast and reproducible sweeps over visual factors. Code: https://avanturist322.github.io/KAGEBench/.