Hi MuJoCo community, Is it possible to simulate soft terrains using MuJoCo? For example, I would like to simulate a robot walking on sand. After reading the documentation, I see that solref and solimp can be used to adjust softness, slip, and the way how contacts interact. However, I am not sure if it is possible to use these parameters to simulate sandy terrain, and what would be their best value combination to achieve it using Mujoco version 1.5 (since I saw solref provide additional features for Mujoco 2.0 when set to negative values). Any help or experience about this would be greatly appreciated. Thanks in advance.