Physics Simulation Engine。NVIDIA PhysX 5 (FOSS BSD・Apex)・Bullet Physics 3.x (Erwin Coumans)・Box2D 3.0 (2D Default)・Chipmunk2D・Jolt Physics (Horizon Forbidden West・Multi-thread)・Rapier 0.20 (Rust・Dimforge)・XPBD eXtended Position-Based Dynamics・Havok (Microsoft買収)・Cannon.js (3D Web)・Verlet Physics・SoftBody+RigidBody+Cloth・¥0 OSS、2026年Jolt+Rapier主流化。