Robot sim stress test: drop 30k cubes to check penetration, MuJoCo defaults are soft
ChongZzZhang · x · 2026-09-14
A technical thread on robotics simulation benchmarking: stress-test solvers by dropping 30,000 10-cm cubes onto a 3-cm resolution random heightfield and checking penetration. Kevin Zakka notes MuJoCo's defaults are soft and can be hardened via solref/solimp, and that PhysX has similar issues simulating heavy robots on thin light objects — feedback is welcome on the mjwarp/mujoco GitHub. ChongZzZhang says he ran solid side-by-side comparisons and param sweeps with Newton but accidentally erased local files and is recovering them from Claude Code history.
Related event: Roboticists Debate Contact Tuning as MuJoCo Defaults Prove Too Soft(4 posts)→
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