SLOPE: Optimistic Potential Landscape Shaping for Model-based Reinforcement Learning

Abstract

Model-based reinforcement learning (MBRL) is sample-efficient but struggles in sparse reward settings. A critical bottleneck arises from the lack of informative gradients in sparse settings, where standard reward models often yield flat landscapes that struggle to guide planning. To address this challenge, we propose **S**haping **L**andscapes with **O**ptimistic **P**otential **E**stimates (**SLOPE**), a novel framework that shifts reward modeling from predicting sparse scalars to constructing informative potential landscapes. SLOPE employs optimistic distributional regression to estimate high-confidence upper bounds, which amplifies rare success signals and ensures sufficient exploration gradients. Evaluations on **30+** tasks across **5** benchmarks and **real-world robotic deployments**, demonstrate that SLOPE consistently outperforms leading baselines in **fully sparse**, **semi-sparse**, and **dense** rewards. The project code is available at https://anonymous.4open.science/r/SLOPE-CF13.