Behavior Trees Library in C++. Batteries included.
This release includes a lot of important changes. This is a non comprehensive list.
With my great surprise, this release seems to be ABI compatible with 4.5.2
ReactiveSequence and ReactiveFallback are unfortunately hard to use correctly. There was a long discussion about what should happen when one of these nodes has multiple asynchronous children and there is no easy answer.
The default behavior is not more similar to version 3.8, but this also means that users must be very careful. Read this issue for details: https://github.com/BehaviorTree/BehaviorTree.CPP/issues/755
We introduce here a new idiom and syntax: the global blackboard. Usually each Subtree (including the main tree) has its own blackboard, isolated from the others, unless we do remapping.
We additionally provide a top-level blackboard that can be accessed from everywhere, without any manual remapping, using the prefix "@"
See example: https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/examples/t19_global_blackboard.cpp
We added a timestamp and a sequence number to each entry in the blackboard (both updated when we set the value).
This allow use to determine if the value we are reading in the blackboard is "new" (since the last time we accessed it) or "obsolate".
We added the methods Blackboard::getStamped and TreeNode::getInputStamped.
Additionally, we added 3 new builtin nodes that use this functionality:
SkipUnlessUpdated: decorator that skip the execution of the children unless an entry was updated, since the last time.WaitValueUpdate: decorator that remains in RUNNING state, unless an entry was updated. Executes the child if it did.WasEntryUpdated: action that returns SUCCESS if an entry was updated, FAILURE otherwise.Details: https://github.com/BehaviorTree/BehaviorTree.CPP/pull/802
We use the operator ".." to concatenate strings and numbers (inspired by Lua). Give this:
prefix := 'value_';
val := 42;
str:= prefix .. val
The variable "str" should contain the string "value_42"
We added a method to send comands directly to the database and to append extra information to a state transition in the Transitions table.
See example https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/examples/t16_sqlite_log.cpp
We simplified the way a custom type can be converted from/to JSON. See the example here: https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/examples/t11_groot_howto.cpp#L13-L27
Related somehow to the JSON convertion mentioned earlier. We add some methods to save/load the state of a blackboard. usefull if you want to reset it correctly, withour destrying it and rebuilding it from scratch.
See this tutorial: https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/examples/t17_blackboard_backup.cpp
Added more convertToString specializations
This release fix some important bugs in the scripting language, most notably in the equal operators, that now support enums and boolean more correctly.
The way default port values is specified is also being changed, to include default pointers to the blackboard too.
Example of how ports with complex types can be initialized.
Note that the case represented in pointC requires the implementation of convertFromString<Point2D>()
static PortsList providedPorts()
{
return {BT::InputPort<Point2D>("input", "no default value"),
BT::InputPort<Point2D>("pointA", Point2D{1, 2}, "default value is [1,2]"),
BT::InputPort<Point2D>("pointB", "{point}", "default value inside blackboard {point}"),
BT::InputPort<Point2D>("pointC", "5,6", "default value is [5,6]"),
BT::InputPort<Point2D>("pointD", "{=}", "default value inside blackboard {pointD}")};
}
But this new syntax is still experimental and will become stable in release 4.6.0
LockedPtr
static_assert when trying to register a derived TreeNode with abstract methodsBT::Any. These ports can connect to each other or to strongly typed portsKeyValueVector metadata() in your custom TreeNode.Any::castPtr added, to access the content of Any without copying.writeTreeXSD() addedThe most notable addition in this release is related to this issue: https://github.com/BehaviorTree/BehaviorTree.CPP/issues/702
The only valid ports are those remapped to a port entry.
This version introduces some refactoring of the Blackboard class and other minor bug fixes.
But the most important change is the introduction of the SubTree Model.
See example ex05_subtree_mode.cpp for details
WakeUpSignal
Both ReactiveSequence and ReactiveFallback were updated to better resemble each other and, partially, the logic they add in version 3.8.
Report any issue you may have.
This is the most improtant change in this release: https://github.com/BehaviorTree/BehaviorTree.CPP/commit/57a26632fb5c237e88e7da5a93a911c861407891
Related to this issue: https://github.com/BehaviorTree/BehaviorTree.CPP/issues/653
Previously, ports created by SetBlackboard would be recognized as strings instead of being considered "typeless" (as they should).
Tutorial 12 was improved to make it easier to register custom type in the "blackboard visualized" of Groot2.
ReactiveFallback was fixed
Pre conditions script will be invoked less often now (i.e., only when really required)