robots/longtable.xml

<mujoco model="longtable">
    <compiler meshdir="assets" texturedir="assets"/>
    <asset>
        <texture name="texmarble" type="cube" file="marble.png"/>
        <material name="matmarble" texture="texmarble" rgba=".7 .7 .7 1"/>
        <mesh name="longtable_mesh" file="longtable.stl" />
    </asset>

    <default>
        <default class="collision">
            <geom condim="3" group="0" />
        </default>
        <default class="visual">
            <geom condim="3" group="1" conaffinity="0" contype="0" />
        </default>
    </default>

    <worldbody>
      <body name="base_link">
        <light mode="fixed" directional="false" diffuse=".8 .8 .8" specular="0.3 0.3 0.3" pos="0 0 -4.0" dir="0 0 1" />
        <geom class="collision" type="box" size="0.5 0.75 .02" rgba="0.266754 0.174546 0.0644028 1" />
        <geom class="collision" type="cylinder" size="0.03 0.39" pos="0.4 -0.7 0.39"  rgba="0.266754 0.174546 0.0644028 1" />
        <geom class="collision" type="cylinder" size="0.03 0.39" pos="-0.4 -0.7 0.39"  rgba="0.266754 0.174546 0.0644028 1" />
        <geom class="collision" type="cylinder" size="0.03 0.39" pos="0.4 0.7 0.39"  rgba="0.266754 0.174546 0.0644028 1" />
        <geom class="collision" type="cylinder" size="0.03 0.39" pos="-0.4 0.7 0.39"  rgba="0.266754 0.174546 0.0644028 1" />
        <geom class="visual" type="mesh" mesh="longtable_mesh" material="matmarble" />
      </body>
    </worldbody>
</mujoco>