Model a White Ball

Before you proceed to code the process_image client node, you have to model a white ball and place it in your Gazebo World scene.

After modeling the white ball, you'll control its position in Gazebo by placing it at different positions in front of the robot’s camera. The process_image client node will be responsible for analyzing the robot’s image and requesting services from the server drive_bot node to drive the robot towards it.

Now, let’s go ahead and model the white ball using the Model Editor tool in Gazebo!

Model Editor

Here’s a reminder of how to open the model editor:

$ gazebo # then Edit-> Model Editor

Insert Sphere

Under the simple shapes menu of the Model Editor tool, click on a sphere and insert it anywhere in the scene.

Edit Size

Double click on the sphere, and change its radius to 0.1 both in Visual and Collision .

Change Color

To change the ball’s color to white, set its Visual Ambient, Diffuse, Specular, and Emissive RGBA values to 1.

Save

Save the white ball model as my_ball under the /home/workspace directory. Then exit the Model Editor tool and go back to the Gazebo main world.

Insert Ball

Now that you are back in the Gazebo main world, you can click on “Insert” and drop the white ball anywhere in the scene.

Relaunch Nodes

Now that you modeled the white ball, relaunch the nodes inside world.launch . Then verify that you can insert a my_ball anywhere inside your world.

Save

Place the white ball anywhere outside of your building structure, so that the robot would not see it. Then, save a copy of this new world under /home/workspace/catkin_ws/src/my_robot/worlds by replacing your old <yourname>.world file. Whenever you launch this newly saved world you should be able to see your building environment, in addition, the white ball.