Isaac Sim 6 Troubleshooting — Large USD Scene Hangs

Purpose

Diagnose Isaac Sim startup hangs, stage-load stalls, MDL/shader compilation freezes, physics stepping blocks, Replicator/Hydra issues, Nucleus latency, and GPU OOM crashes.

Prerequisites

• Built Isaac Sim ($ISAAC_SIM_DIR or _build/linux-x86_64/release).
• NVIDIA GPU with a current driver (nvidia-smi).
• Shell env contract from isaac-sim-orchestrator: $ISAAC_SIM_DIR, $ISAAC_LAB_DIR, $WORKSPACE_DIR.

Limitations

• Symptom lists are heuristic; root causes can overlap across subsystems.
• Some fixes require local Kit builds or NVIDIA internal-only packages.

Troubleshooting