physics-simulation

Apply both UsdPhysics.RigidBodyAPI and UsdPhysics.CollisionAPI to the same prim, then add MassAPI to set mass and center of mass. Splitting the APIs across parent and child prims causes intermittent collision failures.

Use Newton for RL training with thousands of environments, differentiable simulation, or soft bodies; use PhysX for legacy Isaac Sim 5.x scenes. Newton offers Featherstone, MuJoCo, XPBD, SemiImplicit, and VBD solvers with native Warp differentiability.

This usually happens when scaling a Cube prim that has CollisionAPI applied directly, causing PhysX to compute wrong collision bounds. Use a parent xform for position and a child mesh for scale, and enable CCD for fast-moving bodies.

XformCache reads the authored USD layer, but physics writes simulated state to Fabric, not the USD stage. Use RigidPrim.get_world_poses() or Articulation.get_world_poses() from isaacsim.core.experimental.prims after timeline.play() instead.

Use 60-120 Hz for standard scenes, 240 Hz for stacking and contact-rich tasks, and 480 Hz for vibration feeders, spinning bodies, or stiff contact chains. The physics timestep must be at least 4x faster than the highest frequency in the system.

No. PhysX resolves all contacts in a single island simultaneously, distributing momentum across all spheres instead of sequential transfer, and tuning iterations, Hz, or restitution does not fix it. The workaround is scripted analytical momentum transfer between end spheres on detected impact.