XML content

[galou]

I implemented Lua Scripting for BehaviorTree.CPP (details on this below) that uses XML content rather than an input port to allow for multi-line scripts in a nicer fashion. I needed to add support for XML content. Feel free to cherry-pick if interested.

The Lua scripting is a really nice thing. I can access fields of a structure for example. Non-existing variables are queried from the blackboard and I can write back any supported type to the blackboard. I wrote the bindings for the few types that I need (ROS messages) and this lack of generality is the reason why I have these nodes in a separate repo. Would you be interested in this work? Before adding this to the upstream repo, we would need a mean to allow the user to define the Lua bindings for his own types and functions. What would be your preferred way to do it?

[facontidavide]

I am certainly intrigued and want to know more. It would be great if you can show a motivating example

[galou]

A working example of BT xml:

<root main_tree_to_execute="Test" BTCPP_format="4">

  <BehaviorTree ID="Test">

    <Sequence>

      <Log severity="info" message="Behavior tree test_lua_script" />

      <LuaScript>
      <![CDATA[
      -- multi-line script
      info('Lua script on multiple lines')
      warn('Testing `warn`')
      error('Testing `error`')
      info('(2 < 3)?: ' .. tostring(2 < 3))
      ]]>
      </LuaScript>

      <LuaFile uri="package://brick_layer/bt_tests/script.lua" />

    </Sequence>

  </BehaviorTree>

</root>

and the accompanying script.lua:

print("script.lua")

-- Create a PoseStamped message.
p = geometry_msgs.msg.PoseStamped.new()
p.pose.position.x = 123456
print("p.pose.position.x = " .. p.pose.position.x)

-- Get values from the blackboard.
print("const_PALETTE_POSITIVE_PADDING = " .. (const_PALETTE_POSITIVE_PADDING or "nil"))  -- x is defined.
print("y = " .. (y or "nil"))  -- y is not defined.
print("brick_in_l1_pose.pose.position.x = " .. (brick_in_l1_pose.pose.position.x or "nil"))

-- Save values to the blackboard.
to_blackboard("p", p)

-- Copy a PoseStamped and modify a value to check indepedency.
copy_of_brick_in_l1_pose = brick_in_l1_pose
copy_of_brick_in_l1_pose.pose.position.x = 654321
to_blackboard("copy_of_brick_in_l1_pose", copy_of_brick_in_l1_pose)

-- Test the read- and write accessors to the blackboard through the `B` table.
if (B.brick_in_p1_pose == nil) then
  print("B.brick_in_p1_pose is nil")
else
  print("B.brick_in_p1_pose.position.x = " .. B.brick_in_p1_pose.pose.position.x)
end
B.copy_of_brick_in_p1_pose = B.brick_in_p1_pose

-- To test translated_pose and rotated_pose.

local function close(a, b)
  return math.abs(a - b) < 1e-6
end

-- Test translated_pose (C++ translatedPose).
p0 = geometry_msgs.msg.PoseStamped.new()
p0.pose.position.x = 1
p0.pose.position.y = 2
p0.pose.position.z = 3
p0.pose.orientation.x = 0.1618485433953521
p0.pose.orientation.y = 0.35910145565843743
p0.pose.orientation.z = -0.3186393198095994
p0.pose.orientation.w = 0.862160180834205

offset = geometry_msgs.msg.Point.new()
offset.x = 0.1
offset.y = 0.2
offset.z = 0.3

p1 = translated_pose(p0, offset.x, offset.y, offset.z)
p1_ok = (close(p1.pose.position.x, 1.3418572978311953)
         and close(p1.pose.position.y, 1.95321206812806)
	 and close(p1.pose.position.z, 3.144722069328421)
	 and close(p1.pose.orientation.x, p0.pose.orientation.x)
	 and close(p1.pose.orientation.y, p0.pose.orientation.y)
	 and close(p1.pose.orientation.z, p0.pose.orientation.z)
	 and close(p1.pose.orientation.w, p0.pose.orientation.w))
print("p1 ok: " .. tostring(p1_ok))


p2 = translated_pose(p0, offset)
p2_ok = (close(p2.pose.position.x, 1.3418572978311953)
         and close(p2.pose.position.y, 1.95321206812806)
	 and close(p2.pose.position.z, 3.144722069328421)
	 and close(p2.pose.orientation.x, p0.pose.orientation.x)
	 and close(p2.pose.orientation.y, p0.pose.orientation.y)
	 and close(p2.pose.orientation.z, p0.pose.orientation.z)
	 and close(p2.pose.orientation.w, p0.pose.orientation.w))
print("p2 ok: " .. tostring(p2_ok))

-- Test rotated_pose (C++ rotatedPose).
rotation = geometry_msgs.msg.Quaternion.new()
rotation.x = 0.19012781918757307
rotation.y = 0.3726484369487944
rotation.z = 0.3597140900688151
rotation.w = 0.834020580211641

p3 = rotated_pose(p0, rotation.x, rotation.y, rotation.z, rotation.w)
p3_ok = (close(p3.pose.position.x, p0.pose.position.x)
         and close(p3.pose.position.y, p0.pose.position.y)
         and close(p3.pose.position.z, p0.pose.position.z)
         and close(p3.pose.orientation.x, 0.5468199488834077)
	 and close(p3.pose.orientation.y, 0.5019792476912184)
	 and close(p3.pose.orientation.z, 0.03641684464379197)
	 and close(p3.pose.orientation.w, 0.6690878804885766))
print("p3 ok: " .. tostring(p3_ok))

p4 = rotated_pose(p0, rotation)
p4_ok = (close(p4.pose.position.x, p0.pose.position.x)
         and close(p4.pose.position.y, p0.pose.position.y)
         and close(p4.pose.position.z, p0.pose.position.z)
         and close(p4.pose.orientation.x, 0.5468199488834077)
         and close(p4.pose.orientation.y, 0.5019792476912184)
         and close(p4.pose.orientation.z, 0.03641684464379197)
         and close(p4.pose.orientation.w, 0.6690878804885766))
print("p4 ok: " .. tostring(p4_ok))