Troubleshooting

No points appear in Live mode

Press Test Sensor. It prints the sensor's identity, health, and available scan modes. No response means Houdini can't talk to the sensor.
Check the port. Leave Port blank for auto-detect, or set it explicitly (e.g. COM3).
Check the motor lead. The 5V cable must be plugged in — the motor won't spin on data power alone.
Give it a moment. The motor takes about two seconds to spin up on the first cook.
Lots of gaps is normal. On an open desk, most returns are invalid (nothing in range). Point the sensor at a wall to see a dense arc.

The sensor won't connect at all

No Windows chime and nothing new in Device Manager → cable or port problem, not a driver problem. Try a different USB port and swap the data cable — a faulty data cable stops the device enumerating entirely.
Enumerates but silent → check the adapter's baud switch is set to 256000.

"Port is in use" / permission errors

A serial port can only be opened by one program. Close anything else that might hold it:

Another Houdini session in Live mode → set its Mode → Off.
A separate tester/serial app → close it.
A crashed process → the motor may keep spinning; unplug the 5V lead or restart to release the port.

Houdini crashed and the motor is still spinning

The motor runs independently of Houdini once started. Stop it by unplugging the 5V lead (safe — it's just motor power), or reconnect and set Mode → Off.

Guides ended up in my simulation

You fed the solver from Output 0 (Points & Guides). Switch to Output 1 (Points), which strips the rplidar_viz guide geometry. Or turn off the Visualize guides, or delete the rplidar_viz group downstream. See Outputs and Attributes.

Tracking locks onto furniture instead of the hand

Almost always the missing background bake. A real room clusters into 7–11 blobs per scan, and the largest is usually a chair or a wall corner — Single mode is picking the biggest thing present, which is working as designed and isn't what you wanted.

Go Live, clear the interaction area completely, press Bake Background, then turn on Subtract Background. If it still wanders, tighten Blob Size min/max (a hand is roughly 0.05–0.15 m) — that throws out room geometry before clustering ever has to choose. See Background subtraction.

Tracking sees nothing at all after a background bake

You most likely baked while standing in the interaction area, so you were recorded as part of the static scene. Step out and bake again. Re-bake whenever the sensor moves or the room is rearranged.

If it's an object hugging a wall that disappears, lower the Foreground Margin — a return has to be at least that much closer than the background to count as foreground.

Blob ids keep changing / a track keeps restarting

Raise Hold Time. Brief dropouts (a hand turning edge-on) end the track and the next appearance gets a fresh id.
Raise Max Speed if the motion is genuinely fast — a blob that moves further between frames than the gate allows can't be matched to its own track.
Raise Min Points if the blob is breaking apart into specks at the edge of its range.

My solver suddenly sees only a few points

Check Solver Output in the Tracking tab. Set to Blobs, Output 1 carries only the tracked blob points — a handful, by design. Set it back to All Points for the full scan cloud.

Playback shows nothing

Confirm Mode = Playback and a valid file is picked in Recording File (or leave it blank for the newest).
Confirm the Recording Directory points at where your .jsonl files actually live.
Make sure the timeline is playing or you've scrubbed — Playback is driven by the playbar clock.

The asset won't load

RPLidar In ships as .hdalc, which loads only in Houdini Indie and Apprentice, not commercial (FX/Core) licenses.

Changing Scan Mode or Baud pauses the stream

Expected. Changing either restarts the sensor stream, which takes about two seconds.