Lidar Sensors#

An ovrtx lidar scene needs an OmniLidar sensor prim and a RenderProduct whose PointCloud RenderVar requests the channels the application will read. The same USDA pattern is used by C and Python; application code loads the scene, steps the RenderProduct, and maps the output.

Configure the Lidar Prim#

Python Example Scene

    def OmniLidar "Lidar" (
        prepend apiSchemas = ["OmniSensorGenericLidarCoreAPI"]
    )
    {
        token omni:sensor:Core:elementsCoordsType = "CARTESIAN"
        double2 omni:sensor:frameRate = (10, 1)

        double3 xformOp:translate = (0, 0, 1)
        float3 xformOp:rotateXYZ = (90, 0, -90)
        uniform token[] xformOpOrder = ["xformOp:translate", "xformOp:rotateXYZ"]
    }

C Example Scene

    def OmniLidar "Lidar" (
        prepend apiSchemas = ["OmniSensorGenericLidarCoreAPI"]
    )
    {
        token omni:sensor:Core:elementsCoordsType = "CARTESIAN"
        double2 omni:sensor:frameRate = (10, 1)

        double3 xformOp:translate = (0, 0, 1)
        float3 xformOp:rotateXYZ = (90, 0, -90)
        uniform token[] xformOpOrder = ["xformOp:translate", "xformOp:rotateXYZ"]
    }

Use OmniSensorGenericLidarCoreAPI for the generic lidar model. In Z-up scenes, keep the scene Z-up and rotate the lidar prim so sensor +X points in the intended forward direction.

Important Output Attributes#

Attribute	Values	Use
`omni:sensor:Core:elementsCoordsType`	`CARTESIAN` or `SPHERICAL`	Coordinate representation for point tensors.
`omni:sensor:Core:outputFrameOfReference`	`SENSOR`, `WORLD`, or `CUSTOM`	Frame of reference for all outputs.
`omni:sensor:Core:customFrameOfReferenceTrafo`	`[x, y, z, roll, pitch, yaw]`	Custom transform used when the output frame is `CUSTOM`.
`omni:sensor:Core:outputMotionCompensationState`	`NONCOMPENSATED` or `COMPENSATED`	Motion compensation state for outputs.
`omni:sensor:Core:includeInvalidPoints`	`true` or `false`	Preserve invalid returns in the point tensors when true.
`omni:sensor:Core:partialOutputs`	`true` or `false`	Emit partial scans as the sensor sweeps.
`omni:sensor:Core:instantLidar`	`true` or `false`	Emit a full scan every frame for simplified workflows.

Configure PointCloud Output#

Python Example Scene

    def "Render"
    {
        def "Products"
        {
            def RenderProduct "LidarProduct"
            {
                rel camera = </World/Lidar>
                rel orderedVars = [<../../Vars/PointCloud>]
            }
        }

        def "Vars"
        {
            def RenderVar "PointCloud"
            {
                uniform string sourceName = "PointCloud"
                string[] channels = [
                    "Coordinates",
                    "Intensity",
                    "Counts",
                    "TimeOffsetNs"
                ]
            }
        }
    }

C Example Scene

    def "Render"
    {
        def "Products"
        {
            def RenderProduct "LidarProduct"
            {
                rel camera = </World/Lidar>
                rel orderedVars = [<../../Vars/PointCloud>]
            }
        }

        def "Vars"
        {
            def RenderVar "PointCloud"
            {
                uniform string sourceName = "PointCloud"
                string[] channels = [
                    "Coordinates",
                    "Intensity",
                    "Counts",
                    "TimeOffsetNs"
                ]
            }
        }
    }

Request only the channels the consumer needs. Counts and Flags are auto-enabled and delivered like ordinary channel tensors.

Lidar Channels#

Channel	Meaning
`Counts`	Number of delivered point entries. Use it to bound every per-point tensor.
`Coordinates`	Point coordinates in the configured coordinate representation and frame.
`Intensity`	Processed return strength.
`TimeOffsetNs`	Per-point time offset relative to the sensor timestamp.
`Flags`	Per-point status bits. The `VALID` bit is `0x40`.
`EmitterId`, `ChannelId`, `TickId`, `EchoId`	Emitter, detector/channel, scan tick, and return identifiers.
`TickState`	Active scan pattern state for the tick that produced the point.
`MaterialId`, `ObjectId`	Hit material and object identifiers.
`HitNormal`, `Velocity`	Surface normal and velocity at the hit point.

Interpreting Lidar Output#

Within the first Counts[0] entries, a point is valid when Flags[i] & 0x40 is non-zero. Do not compare Flags[i] == 0x40 because other lidar-specific bits can be set at the same time.

With includeInvalidPoints = false, invalid returns are dropped before output. With includeInvalidPoints = true, invalid entries can be present inside the Counts range and must be filtered by Flags before using channels such as Coordinates, Intensity, HitNormal, or Velocity as real returns.

For map/read code, see Reading Sensor PointClouds.