CWRU ROS Camera Plugin

This plugin is intended to resolve some of the functional problems with the old gazebo_ros_pkgs camera plugin:

• Can specify fx and fy directly instead of calculating to FOV.
• Independant horizontal and vertical fx/fy can now be entered.
• cx and cy no longer automatically snap to half the resolution (+0.5 for some reason).
• Camera info and image topics can be named arbitrarily.
• Redundant entry of intrinsics for the actual camera and the camera info (potentially allowing mismatched camera info) has been eliminated.
• Camera coordinates now follow the OpenCV axial convention instead of some random other convention.
• Distortion model now matches that used by OpenCV instead of the normalized model Gazebo uses.

Installation

The improved camera plugin requires Gazebo 11 to function fully. Despite the dire warnings on the Gazebo versioning page, anything in cwru_robotics that worked will Gazebo 9 should work with 11, and installation is a one-time process. Simply follow the instructions from OSRF:

sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'

wget https://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -

sudo apt-get update

sudo apt-get install ros-melodic-gazebo11-dev ros-melodic-gazebo11-plugins ros-melodic-gazebo11-ros ros-melodic-gazebo11-ros-control ros-melodic-gazebo11-ros-pkgs

The package also requires OpenCV, cv_bridge, and image_manip:

sudo apt-get install ros-melodic-opencv-apps ros-melodic-cv-bridge
git clone https://github.com/lucasw/image_manip.git

Use

The utility includes a self-contained camera macro to which all of the necessary parameters are passed as arguments. Simply add <xacro:include filename="$(find cwru_ros_camera)/modular_camera.urdf" /> to the beginning of your file to make the macro available, and then call it:

<xacro:cwru_camera
	parent="camera_optical_link"
	image_topic="/camera/image_raw_color"
	info_topic="/camera/camera_info"
	k1="-0.433351"
	k2=" 0.257538"
	k3="-0.090683"
	p1=" 0.000512"
	p2=" 0.000263"
	
	f_x="1600.0"
	f_y="1600.0"
	c_x="1152"
	c_y="648"
	r_u="2304"
	r_v="1296"
/>

Argument	Description
parent	The link you want the camera to attach to.
image_topic	The ROS topic you want the camera output published to.
info_topic	The ROS topic you want the camera info published to (optional).
k1	K1 distortion parameter (optional).
k1	K1 distortion parameter (optional).
k2	K2 distortion parameter (optional).
k3	K3 distortion parameter (optional).
p1	P1 distortion parameter (optional).
p2	P2 distortion parameter (optional).
f_x	Horizontal focal length.
f_y	Vertical focal length.
c_x	Horizontal image center (px).
c_y	Vertical image center (px).
r_u	Horizontal image size (px).
r_v	Horizontal image size (px).
rupdate_rate	Maximum framrate the camera will update (in hz).

An example use can be found in cwru_ros_camera/urdf/test_camera.urdf. It is run automatically by cwru_ros_camera/launch/test_camera.launch.

References

• vimjay
• gazebo-ros-pkgs