mujoco

<mujoco>
  <include file="scene.xml"/>

  <option cone="elliptic" solver="CG" sleep_tolerance=".01">
    <flag sleep="enable"/>
  </option>

  <default>
    <default class="gripper">
      <geom type="box" size="0.02 0.15 0.02" rgba="0.5 0.5 0.5 1"
            solref="0.001 1" friction="2 0.1 0.1"/>
      <joint type="slide" axis="0 0 1" range="-1 1"/>
      <default class="finger">
        <geom size="0.01 0.06 0.03"/>
        <joint type="slide" range="0 0.1"/>
      </default>
    </default>
  </default>

  <worldbody>
    <body name="gripper_solid" pos="0.2 0.45 0.2">
      <joint name="lift_solid" class="gripper"/>
      <geom class="gripper"/>
      <body name="left_finger_r" pos="0.05 -0.1 0" childclass="finger">
        <joint name="left_slide_r" axis="0 1 0"/>
        <geom rgba="0.8 0.2 0.2 1"/>
      </body>
      <body name="right_finger_r" pos="0.05 0.1 0" childclass="finger">
        <joint name="right_slide_r" axis="0 -1 0"/>
        <geom rgba="0.8 0.2 0.2 1"/>
      </body>
    </body>

    <body name="gripper_hollow" pos="0.2 0 0.2">
      <joint name="lift_hollow" class="gripper"/>
      <geom class="gripper"/>
      <body name="left_finger_s" pos="0.05 -0.1 0" childclass="finger">
        <joint name="left_slide_s" axis="0 1 0"/>
        <geom rgba="0.2 0.8 0.2 1"/>
      </body>
      <body name="right_finger_s" pos="0.05 0.1 0" childclass="finger">
        <joint name="right_slide_s" axis="0 -1 0"/>
        <geom rgba="0.2 0.8 0.2 1"/>
      </body>
    </body>

    <body name="solid" pos=".32 0 .2">
      <flexcomp
        origin="0 0 0" count="8 2 12" cellcount="2 1 2"
        type="grid" name="soft_mesh" dim="3" spacing=".025 .05 .025"
        mass="0.43" radius="0.005" dof="trilinear" rgba="0.7 0.9 0.7 1">
        <edge equality="strain" solref="0.001 1"/>
        <contact selfcollide="none"
              friction="2.0 0.5 0.01"
              solref="0.001 1"
              solimp="0.99 0.999 0.001"/>
      </flexcomp>
    </body>

    <body name="hollow" pos=".32 .45 .2">
      <flexcomp
        origin="0 0 0" count="8 2 12" cellcount="2 1 2"
        type="grid" name="soft_mesh_2" dim="3" spacing=".025 .05 .025"
        mass="0.43" radius="0.005" dof="trilinear" rgba="0.9 0.7 0.7 1">
        <elasticity young="1e5" poisson="0.3" damping="0" elastic2d="bend" thickness="0.03"/>
        <edge equality="strain" solref="0.001 1" solimp="0.99 0.999 0.001"/>
        <contact selfcollide="none"
              friction="2.0 0.5 0.01"
              solref="0.001 1"
              solimp="0.99 0.999 0.001"/>
      </flexcomp>
    </body>
  </worldbody>

  <equality>
    <joint joint1="right_slide_r" joint2="left_slide_r"/>
    <joint joint1="right_slide_s" joint2="left_slide_s"/>
  </equality>

  <actuator>
    <position name="lift_r" joint="lift_solid" kp="400" dampratio="1" ctrlrange="-1 1"/>
    <position name="grasp_r" joint="left_slide_r" kp="10" dampratio="1" ctrlrange="0 5"/>

    <position name="lift_s" joint="lift_hollow" kp="400" dampratio="1" ctrlrange="-1 1"/>
    <position name="grasp_s" joint="left_slide_s" kp="10" dampratio="1" ctrlrange="0 5"/>
  </actuator>
</mujoco>