Add checkerboard texture and update workspace URDFs for better visibility

workspace/workspace.urdf

@@ -11,17 +11,10 @@
       <geometry>
         <mesh filename="plane.obj" scale="0.015 0.015 1"/>
       </geometry>
-      <material name="DarkGrey">
-        <!-- <color rgba="0.2 0.2 0.2 1"/> -->
-        <color rgba="0. 0. 0. 1"/>
+      <material name="Checkerboard">
+        <color rgba="0.5 0.5 0.5 1"/>
+        <texture filename="checkerboard.png"/>
       </material>
     </visual>
-    <!-- <collision>
-      <origin rpy="0 0 0" xyz="0 0 -0.005"/>
-      <geometry>
-        <box size="2.0 3.0 0.01"/>
-      </geometry>
-    </collision> -->
   </link>
 </robot>
-