Two-Pass Shock Propagation for Stable Stacking with Gauss-Seidel 46

Rigid body simulators using the Gauss–Seidel method have been widely adopted for their simplicity, efficiency, and robustness. However, these methods struggle when simulating stable stacking with frictional contact because, unlike global methods, local methods, such as Gauss–Seidel, resolve constraints individually, leading to slow information propagation between bodies. To address this limitation, we introduce two-pass shock propagation, a technique that preserves the advantages of local methods while achieving stable and efficient simulation of frictional stacking without the need to rely on global approaches. The core idea behind two-pass shock propagation is that the upward pass leaves unused impulses on the bottom body, which can be stored and effectively applied during the downward pass. Through extensive experiments, we demonstrate that two-pass shock propagation significantly improves both performance and accuracy.