Preliminary diagnostic comparison. Analytic 4 cm cube, 100 g, initial speed 1 m/s, nominal friction 0.4, gravity 9.81 m/s², timestep 1 ms. No robot, controller or imported mesh.
| Stack | Travel (full recording) | Stays below 1 mm/s (s) | Maximum per-step momentum residual |
|---|---|---|---|
| PhysX CPU / Isaac Sim | 126.920 mm | 0.255 | 5.83e-08 N·s |
| Newton / MuJoCo-Warp | 126.984 mm | 0.266 | 2.76e-07 N·s |
| MuJoCo CPU · slide | 126.986 mm | 0.266 | 3.00e-14 N·s |
| Genesis | 126.956 mm | 0.262 | 8.12e-13 N·s |
The ideal non-rotating Coulomb slider stops after 127.42 mm and 0.25484 s. This is a reference calculation, not ground truth for a compliant, rotating 3D cube. Equal friction coefficients do not equate contact models.
Normal and friction forces are summed on the cube in world coordinates. PhysX uses step impulses divided by dt; other stacks expose native solver force samples. Do not compare individual contact peaks without considering contact count, compliance and force sampling. The audit checks mΔv = ΣFΔt; it verifies recording consistency, not physical accuracy.
