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Davide Faconti
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more docs
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‎docs/images/CrossDoorSubtree.png

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‎docs/tutorial_A_create_trees.md

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@@ -10,7 +10,7 @@ the former for the sake of completeness.
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## How to create your own ActionNodes
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You can find the source code here: [dummy_nodes.h](../sample_nodes/ dummy_nodes.h)
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You can find the source code here: [dummy_nodes.h](../sample_nodes/dummy_nodes.h)
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The default (and recommended) way to create a TreeNode is by inheritance.
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- GripperInterface::open()
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- GripperInterface::close()
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## Tutorial 01: a statically created Tree
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## A static Tree
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``` c++
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#include "dummy_nodes.h"
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```
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## Tutorial 02: a dynamically created Tree
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## A dynamically created Tree
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Give the following XML stored in the file __my_tree.xml__
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‎docs/tutorial_B_node_parameters.md

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- The __static__ method `requiredNodeParameters()` contains a single key/value pair.
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The string "default message" is the default value.
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- Parameters MUST be accessed using the method __getParam()__.
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- Parameters MUST be accessed using the method `getParam()`, preferably in the
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`tick()` method, since this value may change over time.
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``` c++ hl_lines="4 10 22"
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``` c++ hl_lines="5 9 18"
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class SaySomething: public ActionNodeBase
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{
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public:
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// There must be a constructor with this signature
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SaySomething(const std::string& name, const NodeParameters& params):
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ActionNodeBase(name, params) {}
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// It is mandatory to define this static method.
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static const NodeParameters& requiredNodeParameters()
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{
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static NodeParameters params = {{"message","default message"}};
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return params;
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}
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virtual NodeStatus tick() override
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{
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std::string msg;
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std::cout << "Robot says: " << msg << std::endl;
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return BT::NodeStatus::SUCCESS;
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}
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virtual void halt() override {}
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// It is mandatory to define this static method.
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static const NodeParameters& requiredNodeParameters()
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{
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static NodeParameters params = {{"message","default message"}};
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return params;
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}
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};
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```
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If we want the method `getParam()` to be able to parse a string
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and store its value into a Pose2D, we must provide our own specialization
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of `convertFromString<>()`.
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of `convertFromString<T>()`.
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In this case, we want to represent Pose2D as three real numbers separated by
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semicolons.
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``` c++ hl_lines="5"
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``` c++ hl_lines="6"
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// use this namespace
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namespace BT{
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// This template specialization is needed if you want
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// to AUTOMATICALLY convert a NodeParameter into a Pose2D
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template <> Pose2D convertFromString(const std::string& key)
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template <> Pose2D BT::convertFromString(const std::string& key)
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{
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// Three real numbers separated by semicolons
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// Three real numbers separated by semicolons.
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// You may use <boost/algorithm/string/split.hpp> if you prefer
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auto parts = BT::splitString(key, ';');
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if( parts.size() != 3)
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{
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return output;
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}
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}
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} // end naespace
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```
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We now define a synchronous ActionNode called __MoveBaseAction__.
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We now define a __asynchronous__ ActionNode called __MoveBaseAction__.
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The method `getParam()` will call the function `convertFromString<Pose2D>()` under the hood;
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alternatively, we can use the latter directly, for instance to convert the default
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Pose2D goal;
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if( getParam<Pose2D>("goal", goal) == false )
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{
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auto default_goal_value = requiredNodeParameters().at("goal");
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auto default_goal = requiredNodeParameters().at("goal");
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goal = BT::convertFromString<Pose2D>( default_goal_value );
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}
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halt_requested_ = false;
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int count = 0;
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// "compute" for 250 milliseconds or until halt_requested_ is true
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// "compute" for 250 milliseconds or until halt_requested_
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while( !halt_requested_ && count++ < 25)
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{
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SleepMilliseconds(10);
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}
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std::cout << "[ MoveBase: FINISHED ]" << std::endl;
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return halt_requested_ ? NodeStatus::SUCCESS : NodeStatus::SUCCESS;
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return halt_requested_ ? NodeStatus::FAILURE :
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NodeStatus::SUCCESS;
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}
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virtual void halt() override

‎docs/tutorial_D_subtrees.md

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One of the main advantages of Behavior Trees is that they are __intrinsically
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hierarchical__.
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You might have noticed that it is always possible to raise the level of
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abstraction looking one node up in the hierarchy of the tree.
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For example, in the [Introduction](BT_basics.md) page we have seen this tree:
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![FallbackNodes](images/FallbackBasic.png)
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The Sequence calle "Unlock" can be seen as an entire subtree with an arbitrary
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level of complexity.
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BehaviorTree.CPP provides a way to create reusable and composable Subtrees
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that can be included as nodes of a larger and more complex tree.
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## Example: subtrees in XML
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To use the Subtree funtionality, you __don't__ need to modify your
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__cpp__ code, nor your existing TreeNodes.
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Multiple BehaviorTrees can be created and composed in the XML itself.
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``` XML hl_lines="21"
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<root main_tree_to_execute = "MainTree">
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<!--------------------------------------->
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<BehaviorTree ID="DoorClosed">
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<Sequence name="door_closed_sequence">
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<Negation>
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<IsDoorOpen/>
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</Negation>
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<RetryUntilSuccesful num_attempts="4">
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<OpenDoor/>
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</RetryUntilSuccesful>
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<PassThroughDoor/>
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</Sequence>
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</BehaviorTree>
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<!--------------------------------------->
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<BehaviorTree ID="MainTree">
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<Fallback name="root_Fallback">
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<Sequence name="door_open_sequence">
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<IsDoorOpen/>
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<PassThroughDoor/>
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</Sequence>
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<SubTree ID="DoorClosed"/>
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<PassThroughWindow/>
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</Fallback>
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</BehaviorTree>
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<!--------------------------------------->
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</root>
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```
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The corresponding graphical representation is:
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![CrossDoorSubtree](images/CrossDoorSubtree.png)
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