Compatibility with py-trees-js

[arnoldad]

Hi all, happily using py-trees for our project.

I was looking into using py-trees-js for a browser-based visualization, however it seems that the JSON format required for py-trees-js differs (in structure-not just format) from any of the tree outputs available in py-trees. Am i missing something? A way to serialize a shapshot of the running tree into json that is interpretable by the javascript library?

I could of course, write my own way to convert into json meeting that spec, but it seems like there must be some way its already being done in the source...

Any tips?

[stonier]

Sorry for the delay, been a hectic winter.

You're right, the interchange format could be better defined. To boot, some of the json structure contains tree state, some of it contains visualisation details (e.g. colour). I should have separated those concerns. The open source examples of how it is done right now are in the ros repos:

• py_trees_ros_interfaces/BehaviourTree.msg - the tree serialisation, though this is purely for introspection purposes.

NB: Without introducing a really hard constraint mandating behaviours exposing their internal states, it's not possible to have a tree serialisation that can be used for execution. That format also minimises the bandwidth - it only transmits the blackboard delta, since blackboards can get really heavy.

• Populating BehaviourTree.msg in-between tree ticks.

• Converting BehaviourTree.msg -> JSON - relaying the information to the web app

I'll go ahead and create some issues - it would be nice to re-architect some of these interfaces to be more 'standard' and producable from the core py_trees library itself.

[stonier]

What approach did you take in the interim?