Jittery/unstable contacts for a simple STL file of a box resting on a plane? about mujoco

[kurtenkera]

As a further addition to this issue, below is a video of a cylinder primitive geom with 3 stable contact points (these points remain stable over time):

stable_cylinder_contacts.webm

However, when I rest the cylinder on top of a box geom, the contact points are unstable (see below)? This is worrying for me, as these experiments are all performed with MuJoCo's primitive geom objects (not with STL files). I'm worried that if contact forces are unstable for these native MuJoCo objects, there will be equal or increased unreliability for more complex geometries?

unstable_cylinder_contacts.webm

[yuvaltassa]

1. This is working as intended. Jittery objects are a problem, jittery contact points are not. Mesh-plane collisions generate 3 contacts which is all you need for stability. Since there are 4 corners, they are bound to jump around.
2. If this really bothers you (though it shouldn't), try multiccd.