Regions

Regions#

This exercise demonstrates how to define a Region and connect it into the kinematic tree so it moves with a body.

You will:

  • Load the table URDF from the loading worlds exercise

  • Create a region representing the table surface and attach it to the table surface named “top”

  • Move the table and observe that the region follows

0. Setup#

1. Load the table and attach a surface region#

Your goal:

  • Parse table.urdf into a variable named world

  • Find the table body named top in world.bodies

  • Create a thin Region named table_surface and attach it to top via a FixedConnection

  • Store the region in a variable named surface_region

  • Save its initial position in a variable named before_pos

world = URDFParser.from_file(table_urdf).parse()
# Find the table surface body named "top"
top = [b for b in world.bodies if b.name.name == "top"][0]
# Create a thin region at the table surface and attach it to the body "top"
surface_region = Region(name=PrefixedName("table_surface"))
surface_shape = Box(origin=TransformationMatrix(reference_frame=surface_region), scale=Scale(1.0, 1.0, 0.001))
surface_region.area = [surface_shape]
with world.modify_world():
    world.add_kinematic_structure_entity(surface_region)
    world.add_connection(FixedConnection(parent=top, child=surface_region, _world=world))
# Remember the initial pose
before_pos = surface_region.global_pose.to_position().to_np()[:3]

2. Move the table and check the region#

Your goal:

  • Add a Connection6DoF between a new body named root and the current root of the table world

  • Move the table by setting the 6DoF connection’s origin to TransformationMatrix.from_xyz_rpy(x=1.0, y=2.0, reference_frame=world.root) inside a modification block

new_root = Body(name=PrefixedName("root"))
with world.modify_world():
    root_to_table = Connection6DoF(parent=new_root, child=world.root, _world=world)
    world.add_connection(root_to_table)
with world.modify_world():
    root_to_table.origin = TransformationMatrix.from_xyz_rpy(x=1.0, y=2.0, reference_frame=world.root)
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