Mesh-mesh collision not working

[HaoliangWang]

The collisions between two meshes seem to be not working? Although the meshes collides with the ground plane correctly. Here's a simple script to reproduce the behavior. The output video of this script can be found here

demo.mov

The cylinder.stl file used in this script is downloaded from the brax repo: https://github.com/google/brax/tree/241f9bc5bbd003f9cfc9ded7613388e2fe125af6/brax/v1/tests/testdata.

import brax.v1 as brax
import jax
import jax.numpy as jnp
from google.protobuf import text_format
from IPython.display import HTML, display
import brax.v1.io.html as html


CONFIG = """
    dt: 0.05 substeps: 10 friction: 1.0
    gravity { z: -9.8 }
    bodies {
      name: "Mesh1" mass: 1
      colliders { mesh { name: "Cylinder1" scale: 0.1 } }
      inertia { x: 1 y: 1 z: 1 }
    }
    bodies {
      name: "Mesh2" mass: 1
      colliders { mesh { name: "Cylinder2" scale: 0.1 } }
      inertia { x: 1 y: 1 z: 1 }
    }
    bodies { name: "Ground" frozen: { all: true } colliders { plane {} } }
    defaults {
      qps { name: "Mesh1" pos: {x: 0 y: 0 z: 1.5} }
      qps { name: "Mesh2" pos: {x: 0 y: 0 z: 5} rot: {x: 0 y: 90 z: 0} }
    }
    mesh_geometries {
      name: "Cylinder1"
      path: "cylinder.stl"
    }
    mesh_geometries {
      name: "Cylinder2"
      path: "cylinder.stl"
    }
  """


sys = brax.System(text_format.Parse(CONFIG, brax.Config()))
qp = sys.default_qp(0)
qp, _ = sys.step(qp, jnp.array([]))

jit_step = jax.jit(sys.step)

frames = []
for i in range(1000):
    print(i)
    qp, _ = jit_step(qp, jnp.array([]))
    frames.append(qp)

html_string = html.render(sys, frames)
display(HTML(html_string))