Changing argument values to defaults so that they can be overridden.

Author: Juan Ignacio Ubeira

turtlebot_rviz_launchers/launch/view_model.launch

@@ -32,9 +32,9 @@
  -->
 
 <launch>
-  <arg name="base"       value="$(optenv TURTLEBOT_BASE kobuki)"/>  <!-- create, rhoomba -->
-  <arg name="stacks"     value="$(optenv TURTLEBOT_STACKS hexagons)"/>  <!-- circles, hexagons -->
-  <arg name="3d_sensor"  value="$(optenv TURTLEBOT_3D_SENSOR kinect)"/>  <!-- kinect, asus_xtion_pro -->
+  <arg name="base"       default="$(optenv TURTLEBOT_BASE kobuki)"/>  <!-- create, rhoomba -->
+  <arg name="stacks"     default="$(optenv TURTLEBOT_STACKS hexagons)"/>  <!-- circles, hexagons -->
+  <arg name="3d_sensor"  default="$(optenv TURTLEBOT_3D_SENSOR kinect)"/>  <!-- kinect, asus_xtion_pro -->
 
   <include file="$(find turtlebot_bringup)/launch/includes/robot.launch.xml">
     <arg name="base" value="$(arg base)" />