Environment Generation
Contact sensor creation
Contact sensors are automatically created during environment configuration to detect physical contacts between objects and the gripper.
How sensors are created
When environments are generated, RoboLab dynamically creates contact sensors based on two configuration fields:
contact_object_list: List of object names to monitor (defined in the Task class)@dataclass class MyTask(Task): contact_object_list = ["table", "apple", "plate"] # <-- contact sensors are created for these objects. scene = import_scene("my_scene.usda", contact_object_list)contact_gripper: Dictionary mapping gripper names to prim path patterns (defined in robot configs, e.g.,robolab/robots/droid.py)
Three types of sensors are created. In the code, objects are separated by two underscores __.
| Sensor Type | Naming Pattern | Purpose |
|---|---|---|
| Batch gripper sensor | {gripper}__all_objs |
Efficient batch queries for gripper vs all objects |
| Pairwise gripper-object | {gripper}__{object} |
Individual gripper-object contact checks |
| Pairwise object-object | {object1}__{object2} |
Object-to-object contact detection |
Force direction convention
The sensor's force_matrix_w returns forces on the sensor body from the filter body. When retrieving contact forces via WorldState.get_contact_force(body1, body2):
- If sensor exists as
body1__body2: force is returned as-is - If sensor exists as
body2__body1(reversed): force is negated to give force onbody1frombody2
This ensures get_contact_force(obj, surface) returns an upward force (positive Z) when an object rests on a surface.
Usage
This information is accessible via RoboLab's world state:
# Querying contact forces (robolab/core/world/world_state.py)
world = get_world(env)
force = world.get_contact_force("apple", "table") # Force on apple from table
supported = world.is_supported_on_surface("apple", "plate") # Contact force cone check
Key files
robolab/core/sensors/contact_sensor_utils.py: Sensor creation and lookup functionsrobolab/core/world/world_state.py:get_contact_force(),is_supported_on_surface()