Pinch — tdlidar_pinch

Pinch thumb to index in mid-air and it becomes a smooth fader for any TouchDesigner parameter.

Category: Camera & Vision · Tier: Free · Needs: rear camera (hand-derived; no LiDAR required)

What it does

Reports a single number: how far apart your thumb tip and index tip are, measured on the first detected hand. The distance is normalized against the size of your palm, so it reads roughly the same whether your hand is near or far from the camera — fingers touching is near 0, fingers spread is the high end. It’s the air-fader: one clean value you map to volume, blur, speed, anything.

OSC in

| address | type | range | rate | |—|—|—|—| | /tdlidar/pinch | float | thumbTip↔indexTip distance, palm-normalized (~0 closed, larger = open) | per frame |

Outputs

out1 (CHOP) — one channel, pinch. The node tile previews out1.

Parameters

| par | default | what it does | |—|—|—| | OSC Port | 9000 | UDP port to listen on (match the app) |

Quick start (beginner)

  1. In the app, enable Hands (Pinch rides the hand pass) and show one hand to the rear camera.
  2. Drop the Pinch op — internally it’s just an OSC In CHOP → Select CHOP → out1 picking the tdlidar/pinch channel.
  3. Touch thumb to index, then spread them: the pinch value sweeps from ~0 upward.
  4. Wire out1 into the parameter you want to ride (e.g. a Blur TOP Filter Size) and pinch to drive it live.

Advanced patterns

  • Map to a useful range: raw pinch isn’t 0–1. Run out1 → Math CHOP (or Range CHOP) to remap your comfortable closed/open span onto exactly the target range, and clamp the ends so it can’t overshoot.
  • Smooth the fader: a Lag CHOP (lag ~0.1) turns a slightly jittery pinch into a buttery fader; raise the lag for slow, cinematic moves.
  • Pinch-to-click: threshold the value with a Logic / Trigger CHOP so a full pinch fires a one-shot bang (advance a slide, take a snapshot) instead of acting as a continuous fader.
  • Two faders from two hands: Pinch uses only the first hand. For an independent second axis, derive thumb↔index distance from the Hand op’s right landmarks and run it through the same Range → Lag chain.

Gotchas

  • It’s normalized, not metric — and not 0–1. Always remap with a Math/Range CHOP to your own observed closed/open values; don’t assume a fixed scale.
  • First hand only. If two hands are up, pinch follows whichever the app classifies first; it won’t average or pick the closer one.
  • Goes stale when no hand is detected. With no hand in frame the channel holds its last value rather than dropping to 0 — gate on the Hand op’s …/count if a held fader between gestures would cause trouble.