Tape Measure Plugin

[JShep1]

An initial prototype of the tape measure plugin.

Hotkey for new measurement: m

See also #458 for right click mid-measure-action cancellation.

I made a few decisions here that I think we can discuss and possibly change:

• I added gui events for a mouse hover and the left click event in Scene3D. My reasoning was primarily that I needed to get the data from the ScreenToScene() call within Scene3D but didn't want to couple this plugin together with Scene3D itself. I'm not sure if this is the best route to go, but it was the best I could think of for now, are there any other better ideas as to how to do this? I was thinking we could eventually move the gui events header to ign-common so that ign-gui can contain plugins like this that don't depend on the ecm but still need data from the Scene3D would this be a reasonable path? Any foreseen issues?
• I only added singular measurements for now. There are a couple main reasons. The first is that text markers are only currently supported in OGRE 1.x, if we had multiple markers in a OGRE 2 scene, the user would have no way of knowing what the distance would be for each measurement. For this reason, I simply put the distance for the measurement within the gui window. The second reason is that we have no way of being able to selectively remove specific measurements if multiple existed within the scene. We will need to add support for user interaction with markers for this to be possible.

Additionally, @ColeOSRF is working on new icons for the measurement button and the delete button.

Example:

Depends on gazebosim/gz-gui#148 for gui events

[JShep1]

Design doc for this plugin can be found here https://github.com/ignitionrobotics/design/blob/master/tape_measure_tool.md

[chapulina]

Works well for me.

I don't think that this can be avoided if we use the MarkerManager, but a user could send a DELETE_ALL at any time and mess up the tape measure's markers. I think the least we can do is be prepared in case this happens, by never assuming the markers we placed will be there.

I tried calling the following service while using the tape measure, and the worst I could get is that one of the end markers disappears, but not both. You can also end up with no markers, but the distance is non-zero. I think these aren't big issues, but just something to keep in mind.

ign service -s /marker --reqtype ignition.msgs.Marker --reptype ignition.msgs.Empty --timeout 2000 --req "action: DELETE_ALL"

[chapulina]

I know this will probably be complicated to achieve with markers, but I'll just make an observation for the future.

The fixed scale means that the points may be too big or too small depending on what's being simulated and the user's zoom level. Maybe they're too big to measure the distance between fingers of a robot hand, but too small when measuring the size of a road. One option would be to scale it according to the zoom level like it's done for the transform controls:

[JShep1]

Good point, I believe that functionality is coming from this line? After thinking about it for a second, I think the effect comes from the world "moving away" and the visual gizmo staying the same size. @ColeOSRF do you know how this tool is usually handled in large vs small scenarios and when the user is zooming in and out?

[chapulina]

Just dropping a cross-reference link here. This requires: gazebosim/gz-gui#148

[chapulina]

Works for me! Before merging this, we need to:

• Merge Add gazebo gui events gz-gui#148
• Release ign-gui with ☝️
• Update the minimum required ign-gui version here

[chapulina]

🚀