# Sensing

> Sensor nodes read a video stream or the device and give back fixed, labelled control lanes from 0 to 1.

Source: https://docs.tune.toys/concepts/sensing/

Sensing nodes turn what a camera sees, or how a device moves, into control lanes you can plug into any parameter.

## What it does

[Hands](https://docs.tune.toys/nodes/sense.hands/), [Face](https://docs.tune.toys/nodes/sense.face/), [Body](https://docs.tune.toys/nodes/sense.body/) and [Gestures](https://docs.tune.toys/nodes/sense.gesture/) take a `video` input from a source and emit a fixed, labelled control output with values from 0 to 1. [Motion](https://docs.tune.toys/nodes/sense.motion/) reads the device's accelerometer and gyroscope and has no input. Each lane has a fixed label and position, listed on the node's page.

The tracking nodes run MediaPipe models in the browser. A model downloads only after the person consents, with its size shown, and is cached afterwards. Video and sensor data stay on the device; the Toy never records or uploads them. When tracking is lost the lanes hold their last values and the `present` lane falls after 220 ms.

A sensor's output is wide, so it cannot go straight into a parameter. Use [Select lanes](https://docs.tune.toys/nodes/ctl.select/) with `"audio": {"channels": 1, "firstChannel": N}` to pick one lane (lanes count from 1; for example the Face `mouth` lane is lane 9), then plug that one-lane cable into a parameter socket such as `{ "node": "filter", "port": "@cutoff" }`. Shape it first with [Scale](https://docs.tune.toys/nodes/ctl.scale/) or [Smooth](https://docs.tune.toys/nodes/ctl.smooth/).

Video needs the browser's WebGPU engine for pictures; sensing runs where the browser supports it. The Player and exports do not run video or sensing yet.

## Tips

- Connecting all lanes straight to a one-lane input is a width conflict and is rejected.
- Use `present` to mute or fade a sound when nobody is in view.

## See also

[Video](https://docs.tune.toys/concepts/video/), [Control lanes](https://docs.tune.toys/concepts/control-lanes/), [Select lanes](https://docs.tune.toys/nodes/ctl.select/), [Smooth](https://docs.tune.toys/nodes/ctl.smooth/).