Black scene in Gazebo when launching robot

edit

I've been trying to spawn a robot that I designed through SolidWorks in Gazebo through a launch file. I've been able, after testing with other urdf files, to isolate the problem in the urdf file of my robot. I've been checking and rechecking, rebuilt, retried, but I haven't been able to find it. I don't know if there is any additional tag that I need to put or what.

The file is the following one:

    <?xml version="1.0" encoding="utf-8"?>
<!-- This URDF was automatically created by SolidWorks to URDF Exporter! Originally created by Stephen Brawner (brawner@gmail.com)
     Commit Version: 1.6.0-1-g15f4949  Build Version: 1.6.7594.29634
     For more information, please see http://wiki.ros.org/sw_urdf_exporter -->
<robot
  name="robot" xmlns:xacro="http://ros.org/wiki/xacro">

  <gazebo>
    <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
      <robotNamespace>/myrobot</robotNamespace>
    </plugin>
  </gazebo>

  <link
    name="base_link">
    <inertial>
      <origin
        xyz="0.0123124347014089 0.0505768275758483 0.15"
        rpy="0 0 0" />
      <mass
        value="0.630838996758129" />
      <inertia
        ixx="0.000486003425974024"
        ixy="-4.0867892138948E-20"
        ixz="-1.48375522376699E-20"
        iyy="0.00152536968068318"
        iyz="-1.84823168117317E-21"
        izz="0.00132299502191583" />
    </inertial>
    <visual>
      <origin
        xyz="0 0 0"
        rpy="0 0 0" />
      <geometry>
        <mesh
          filename="package://urdf_screencast/meshes/base_link.STL" />
      </geometry>
      <material
        name="">
        <color
          rgba="0.749019607843137 0.749019607843137 0.749019607843137 1" />
      </material>
    </visual>
    <collision>
      <origin
        xyz="0 0 0"
        rpy="0 0 0" />
      <geometry>
        <mesh
          filename="package://urdf_screencast/meshes/base_link.STL" />
      </geometry>
    </collision>
  </link>

  <link
    name="Link_1">
    <inertial>
      <origin
        xyz="0.0494537742604109 0.0123643555558083 0.0416713225379099"
        rpy="0 0 0" />
      <mass
        value="0.0589092038804175" />
      <inertia
        ixx="5.20170683662542E-05"
        ixy="-2.9517247336885E-07"
        ixz="3.25086601912495E-07"
        iyy="0.000116905037934805"
        iyz="1.38108194550258E-08"
        izz="7.57088192052892E-05" />
    </inertial>
    <visual>
      <origin
        xyz="0 0 0"
        rpy="0 0 0" />
      <geometry>
        <mesh
          filename="package://urdf_screencast/meshes/Link_1.STL" />
      </geometry>
      <material
        name="">
        <color
          rgba="0.749019607843137 0.749019607843137 0.749019607843137 1" />
      </material>
    </visual>
    <collision>
      <origin
        xyz="0 0 0"
        rpy="0 0 0" />
      <geometry>
        <mesh
          filename="package://urdf_screencast/meshes/Link_1.STL" />
      </geometry>
    </collision>
  </link>

  <joint
    name="fix_bottom_up"
    type="fixed">
    <origin
      xyz="0.10878 -0.03875 0.09475"
      rpy="1.5708 0 3.1416" />
    <parent
      link="base_link" />
    <child
      link="Link_1" />
    <axis
      xyz="0 0 1" />
  </joint>

  <link
    name="Link_2">
    <inertial>
      <origin
        xyz="-0.0525323569937009 0.051803889250599 0.0412124918069813"
        rpy="0 0 0" />
      <mass
        value="0.0237376231761265" />
      <inertia
        ixx="1.70730388713891E-05"
        ixy="1.06258051836124E-08"
        ixz="4.35505916910561E-07"
        iyy="5.0620665601632E-05"
        iyz="1.32281442514884E-07"
        izz="3.48311372724787E-05" />
    </inertial>
    <visual>
      <origin
        xyz="0 0 0"
        rpy="0 0 0" />
      <geometry>
        <mesh
          filename="package://urdf_screencast/meshes/Link_2.STL" />
      </geometry>
      <material
        name="">
        <color
          rgba="0.749019607843137 0.749019607843137 0.749019607843137 1" />
      </material>
    </visual>
    <collision>
      <origin
        xyz="0 ...