Affordances#

An affordance is an interaction that an object makes available to the robot — opening a door, pressing a button, turning a knob. By attaching affordances to objects, Arena gives tasks a standard interface to interact with them, regardless of the specific object.

Examples of Pressable and Openable objects — Two examples of affordances. A drill and coffee machine are **Pressable** (`is_pressed()`, `press()`); a microwave and cardboard box are **Openable** (`is_open()`, `close()`).#

How an object gets an affordance#

Affordances are added to an object through multiple inheritance. The microwave inherits from both LibraryObject and Openable, and declares the joint name that the affordance controls:

@register_asset
class Microwave(LibraryObject, Openable):
    name = "microwave"
    tags = ["object", "openable"]
    object_type = ObjectType.ARTICULATION

    # Openable affordance parameters
    openable_joint_name = "microjoint"
    openable_threshold = 0.5  # open if joint > threshold, closed otherwise

The Openable mixin implements is_open() and close() using the joint name provided — no further setup needed.

Why this matters#

Because tasks are written against the affordance interface rather than a specific object, the same task works with any object that has the right affordance. OpenDoorTask works with the microwave, a fridge, a cabinet — any Openable. This is what makes tasks modular and reusable across different scenes.