Sensor Schema

The Sensor Schema extends OpenUSD with typed prim schemas for the physics-based sensors in Isaac Sim. All sensor schemas inherit from a common IsaacBaseSensor base class and are defined in the isaacsim.robot.schema extension alongside the Robot Schema.

The schema source lives in source/extensions/isaacsim.robot.schema/sensor_schema/SensorSchema.usda.

Base Sensor

IsaacBaseSensor is the abstract base class for all typed sensor prims. It inherits from Xformable, so every sensor has a position and orientation on the stage.

Attribute	Type	Description
enabled	Bool	Set to True to enable this sensor, False to disable.

Contact Sensor (IsaacContactSensor)

IsaacContactSensor measures contact forces between the prim it is attached to and other prims in the scene. It inherits from IsaacBaseSensor.

See Contact sensor for usage documentation.

Attribute	Type	Description
threshold	Float2	Min and max force detected by this sensor, in (kg) * (stage length unit) / (second)^2.
radius	Float	Radius of the contact sensor sphere, in stage length units. A value of -1 uses the prim’s collision geometry.
color	Float4	Color of the contact sensor visualization sphere (R, G, B, A).
sensorPeriod	Float	Deprecated since isaacsim.robot.schema 6.2.0. Only used by the deprecated isaacsim.sensors.physx extension. Time between measurements in simulator seconds.

IMU Sensor (IsaacImuSensor)

IsaacImuSensor measures linear acceleration, angular velocity, and orientation of the prim it is attached to. It inherits from IsaacBaseSensor.

See IMU sensor for usage documentation.

Attribute	Type	Description
sensorPeriod	Float	Deprecated since isaacsim.robot.schema 6.2.0. Only used by the deprecated isaacsim.sensors.physx extension. Time between measurements in simulator seconds.
linearAccelerationFilterWidth	Int	Number of linear acceleration measurements used in the rolling average filter.
angularVelocityFilterWidth	Int	Number of angular velocity measurements used in the rolling average filter.
orientationFilterWidth	Int	Number of orientation measurements used in the rolling average filter.

Raycast Sensor (IsaacRaycastSensor)

IsaacRaycastSensor is a physics-raycast-based sensor with explicit per-ray origin offsets, direction vectors, and optional time offsets. It inherits from IsaacBaseSensor and is used by the isaacsim.sensors.experimental.physics extension.

See Physics raycast sensor for usage documentation.

Origins and directions are specified in the sensor prim’s local coordinate frame. At each physics step the sensor’s world transform is computed from the current rigid-body pose, optionally extrapolated forward using linear/angular velocity when a non-zero rayTimeOffset is specified. Each ray’s local origin and direction are then transformed into world space for the raycast.

All attributes are read once when the sensor is first evaluated after simulation starts. Changing attribute values while the simulation is playing has no effect; stop and restart the simulation to pick up changes.

Attribute	Type	Description
numRays	UInt	Number of rays cast by this sensor. rayOrigins and rayDirections must each have exactly this many elements.
minRange	Float	Minimum detection range in stage length units. Rays start at origin + direction * minRange.
maxRange	Float	Maximum detection range in stage length units.
rayOrigins	Float3[]	Per-ray origin translations in the sensor’s local coordinate frame.
rayDirections	Float3[]	Per-ray cast direction vectors in the sensor’s local coordinate frame. Vectors are normalized before use.
rayTimeOffsets	Float[]	Per-ray time offsets in seconds. When provided, only rays whose time offsets fall within the current physics step’s time window are fired. The sweep period equals max(rayTimeOffsets). If empty, all rays fire every step.
outputFrameOfReference	Token	Coordinate frame for hit positions and normals: SENSOR (default) or WORLD.
reportHitPrimPaths	Bool	When True, the sensor reading includes the USD prim path of each hit surface.

Deprecated Sensor Schemas

The following sensor schemas are defined in SensorSchema.usda but are deprecated:

• IsaacLightBeamSensor – Deprecated since isaacsim.robot.schema 6.2.0. Use IsaacRaycastSensor with isaacsim.sensors.experimental.physics instead. See Migrating to the physics raycast sensor.

The IsaacRtxLidarSensorAPI and IsaacRtxRadarSensorAPI are applied API schemas for the RTX sensor pipeline and are not physics-based sensors. See RTX Sensors for RTX sensor documentation.