Request FrameAligned view, as in ROS1

[jowaibel]

In ROS1's rviz, there used to be a FrameAligned view that allowed to align the view exactly with a target frame. This is crucial for, e.g., a flight simulator where the user wants to see the view of the aircraft moving in 6 degrees of freedom. (In this case, the target frame would be the body frame.)

ThirdPersonFollower would work for a robot that moves on the horizontal plane only but not for an aircraft moving and rotating in 3 dimensions.

I cannot understand why this feature has not been ported and nobody asked for it since rviz2 came out. It would highly appreciate if it could be added to rviz2. Thank you very much!

[christophebedard]

It was simply never ported. PRs are welcome 😄

[jowaibel]

Hi @christophebedard, I have not worked with the rviz source code before. If you could sketch what needs to be done to do the work and point me to the right fields, I will see what I can do.

[christophebedard]

I've only looked at the RViz source code once myself, but any time is a good time to learn!

The plugin is defined in an XML file:

• In ROS 1, the rviz/FrameAligned plugin is defined here: https://github.com/ros-visualization/rviz/blob/250c0c2875758953f98f3b1982d11b55f527b295/plugin_description.xml#L294-L298
• In ROS 2, it would be added somewhere here:

  rviz/rviz_default_plugins/plugins_description.xml

  Lines 450 to 497 in 7b31f1c

  	<!-- View Controller plugins -->
  	<class
  	name="rviz_default_plugins/FPS"
  	type="rviz_default_plugins::view_controllers::FPSViewController"
  	base_class_type="rviz_common::ViewController"
  	>
  	<description>
  	Control the camera like in a First Person Shooter game: drag left to look left, etc.
  	</description>
  	</class>
  	<class
  	name="rviz_default_plugins/Orbit"
  	type="rviz_default_plugins::view_controllers::OrbitViewController"
  	base_class_type="rviz_common::ViewController"
  	>
  	<description>
  	Makes it easy to move around a given point in space, looking at it from any angle.
  	</description>
  	</class>
  	<class
  	name="rviz_default_plugins/TopDownOrtho"
  	type="rviz_default_plugins::view_controllers::FixedOrientationOrthoViewController"
  	base_class_type="rviz_common::ViewController"
  	>
  	<description>
  	Orthographic projection, seen from the top.
  	</description>
  	</class>
  	<class
  	name="rviz_default_plugins/XYOrbit"
  	type="rviz_default_plugins::view_controllers::XYOrbitViewController"
  	base_class_type="rviz_common::ViewController"
  	>
  	<description>
  	Makes it easy to move around a given point on the XY plane, looking at it from any angle.
  	</description>
  	</class>
  	<class
  	name="rviz_default_plugins/ThirdPersonFollower"
  	type="rviz_default_plugins::view_controllers::ThirdPersonFollowerViewController"
  	base_class_type="rviz_common::ViewController">
  	<description>
  	Follow a target frame and turn the viewing direction with the yaw of the target frame.
  	</description>
  	</class>

You can see that each plugin definition in the XML file has a type, which is essentially a class name. Each plugin class is registered in its .cpp file:

• In ROS 1, the rviz::FrameViewController class is registered here (see the FrameViewController class above): https://github.com/ros-visualization/rviz/blob/250c0c2875758953f98f3b1982d11b55f527b295/src/rviz/default_plugin/view_controllers/frame_view_controller.cpp#L165
• In ROS 2, for example, this is how the rviz_default_plugins::view_controllers::FPSViewController class is registered:

  rviz/rviz_default_plugins/src/rviz_default_plugins/view_controllers/fps/fps_view_controller.cpp

  Lines 265 to 266 in 7b31f1c

  	PLUGINLIB_EXPORT_CLASS(
  	rviz_default_plugins::view_controllers::FPSViewController, rviz_common::ViewController)

Now, you can see that the ROS 1 FrameViewController class extends the FPSViewController class: https://github.com/ros-visualization/rviz/blob/250c0c2875758953f98f3b1982d11b55f527b295/src/rviz/default_plugin/view_controllers/frame_view_controller.h#L42. This FPSViewController class is itself a plugin, and it also exists in ROS 2, which I linked to above.

Therefore, I believe you just need to create a FrameViewController class that extends the existing FPSViewController class and essentially copy the logic from the ROS 1 implementation of FrameViewController. Looking at the ROS 1 FPSViewController class and the ROS 2 FPSViewController class, there are some differences, so you'll most likely have to adapt some things when porting FrameViewController to ROS 2.

Let me know if something isn't clear or if you have any questions.