Physically plausible balloon dynamics via position-based constraints and geodesic-weighted forces

This paper presents a lightweight balloon-dynamics method, built on the Position-Based Dynamics (PBD) framework, that reproduces real-time inflation-deflation-rotation as air is injected and released. Unlike volume/CFD approaches that require expensive fluid-structure coupling, our method avoids explicit fluid simulation by combining Bernoulli-derived reaction forces with PBD distance and volume constraints. Rotation is modeled as a global rigid-body motion (single rotation/quaternion update about the center of mass), while local shape changes are handled through constraint-based position correction-eschewing cluster-level or per-vertex local twisting. Geodesic-distance weighting of reaction forces and the separate treatment of translational and rotational components improve physical plausibility; minimal iterations and rigid-body rotation approximation preserve computational efficiency. Experiments on meshes with diverse geometries and mass distributions show consistent real-time performance on high-resolution models while capturing the characteristic balloon behaviors. The approach is well-suited for interactive applications such as games, VR/AR, and real-time physics-based content.