rigidax

Differentiable rigid-body kinematics and dynamics in JAX, compiled from MJCF and URDF by MuJoCo, with physical parameters as pytree leaves so jax.grad and vmap run over masses, inertias, offsets and gravity. Batched inverse kinematics and motion retargeting; every quantity is ground-truth tested against MuJoCo on random trees plus G1/A2/Panda, and against Pinocchio.