mujoco

<mujoco model="example">
  <compiler angle="radian" autolimits="true"/>
  <default class="main">
    <geom rgba="0.8 0.6 0.4 1"/>
  </default>
  <asset>
    <texture type="skybox" builtin="gradient" rgb1="1 1 1" rgb2="0.6 0.8 1" width="256" height="1536"/>
  </asset>
  <worldbody>
    <light pos="0 1 1" dir="0 -0.707107 -0.707107" diffuse="1 1 1"/>
    <body pos="0 0 1">
      <joint pos="0 0 0" type="ball"/>
      <geom size="0.06 0.2" pos="0 0 -0.2" type="capsule"/>
      <body pos="0 0 -0.4">
        <joint pos="0 0 0" axis="0 1 0"/>
        <joint pos="0 0 0" axis="1 0 0"/>
        <geom size="0.04 0.15" pos="0.15 0 0" quat="0.707107 0 -0.707107 0" type="capsule"/>
        <body pos="0.3 0 0">
          <joint pos="0 0 0" axis="0 1 0"/>
          <joint pos="0 0 0" axis="0 0 1"/>
          <geom size="0.1 0.08 0.02" pos="0.1 0 0" type="ellipsoid"/>
          <site name="end1" pos="0.2 0 0" size="0.01"/>
        </body>
      </body>
    </body>
    <body pos="0.3 0 0.1">
      <joint type="free"/>
      <geom size="0.07 0.1" type="cylinder"/>
      <site name="end2" pos="0 0 0.1" size="0.01"/>
    </body>
  </worldbody>
  <tendon>
    <spatial range="0 0.6" width="0.005">
      <site site="end1"/>
      <site site="end2"/>
    </spatial>
  </tendon>
</mujoco>