Fixing Bodies Dynamically

[tomalner18]

Hi, I'm looking for a way to fix/lock a body in its current position. Is it possible, for example, to set the joint ranges - in this case of a body with a 'free' joint - to the object's current q during a rollout. If you have any kind of example that would be amazing, thanks!

[btaba]

Hi @tomalner18 , thanks for using brax!
You'd want to edit the dof limits

brax/brax/base.py

Line 294 in 3b72c95

limit: Tuple[jp.ndarray, jp.ndarray]

here's an example

@jax.jit
def do_stuff(sys, state):
  state = pipeline.step(sys, state, jp.zeros(sys.act_size()))
  sys = sys.replace(dof=sys.dof.replace(limit=(sys.dof.limit[0].at[0].set(0), sys.dof.limit[1].at[0].set(0))))
  state = pipeline.step(sys, state, jp.zeros(sys.act_size()))
  return state

let us know if that works!