Simulation parameters for static objects

Hello, there.

Intent: I’m trying to restrict the movement of agents in their environment by creating wall-like box assets/actors and positioning them around the area.

Problem: I’m unable to make the walls fixed in place. Moreover, the walls appear to slowly drift apart on their own.

  • The effect persists even if the walls are not close at the start of the simulation.
  • The drift is affected by some parameters, but never completely gone at all scales (shorter walls seem more stable).

Question: How could one make some objects (which may be positioned side by side, i.e. close enough to be considered in contact) fixed in place, i.e. not subject to physics? I assumed that asset_options.fix_base_link = True could serve this purpose, but it didn’t suffice in this case.

Thank you for your time and responses.


Setting asset_options.fix_base_link to True is the right way to achieve this. There shouldn’t be any drift. Would it be possible for you to share a code snippet that reproduces the issue?


While preparing the snippet, it turned out to be a silly mistake of mine (due to which different asset options were in effect, hence why fix_base_link did not work) and my puzzlement (at why sometimes there was drift and other times there wasn’t) erroneously pointed my attention towards simulation parameters.

Thank you for confirming the correct approach and my apologies for the oversight.

For completeness, I’m attaching a basic example, which (in the case of fix_base_link remaining turned off) highlights the interplay of args.dt, args.substeps, and args.env_size (custom parameter of length of the sides of the environment and that of its bounding walls/fence): The default settings should result in drift that is visible to the viewer, while a small change (e. g. lowering args.substeps=3 from 4) can eliminate it. (3.4 KB)

Regardless of this behaviour, I consider the case closed/solved.

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