Composite Objects are any models that have sub-objects that can be referenced to in the TDW API.
Each sub-object may also be a mechanism (a TDW-specific idiom). Currently, the following mechanism have been implemented:
| Mechanism | Behavior | Example |
|---|---|---|
hinge |
Swings freely on a pivot point around an axis. | A box with a lid |
motor |
Can rotate on a pivot point around an axis by applying a target velocity and a force magnitude. | A helicopter propeller |
spring |
Can rotate on a pivot point around an axis by applying a target position. The motion will appear "spring-like" | Jack-in-the-box |
light |
Can be turned on or off. | A lightbulb |
none |
(No mechanism) | A chest of drawers |
Each sub-object has a Rigidbody, segmentation color, etc. All of this can be retrieved from output data like any other object (e.g. via send_transforms or send_rigidbodies). The difference is that each sub-objects ID is defined by Unity at runtime rather than assigned by the user in a controller.
To receive a map of sub-objects in a composite object, send the send_composite_objects command to receive CompositeObjects data.
Certain commands can only be sent to certain types of sub-objects (e.g. set_motor only works with motors). For a list of all sub-object commands, see the Command API documentation under "SubObjectCommand".
There are two example controllers for composite objects:
composite_object.py(Tests output data and sub-object commands)open_box.py(Basic demo of a Sticky Mitten Avatar opening a box with a lid)