Hand — tdlidar_hand

Raise one or both hands in front of the rear camera and have fully-rigged finger skeletons drive your scene.

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

What it does

Tracks up to two hands and rebuilds each as a 21-landmark skeleton — wrist, plus four joints per finger out to each fingertip. The op plots those landmarks as points and draws the finger bones, locking each bone to a fixed length so a finger never stretches or warps as the hand moves toward or away from the camera. Use it to puppet geometry, scrub parameters with a fingertip, or spawn particles from the tips.

OSC in

| address | type | range | rate | |—|—|—|—| | /tdlidar/body/hands/count | int | number of hands (0–2) | per frame | | /tdlidar/body/hands/distance | float | hand distance, metres | per frame | | /tdlidar/body/hands/frame | int | heartbeat — increments every frame so TD knows data is live even when the hand is still | per frame | | /tdlidar/body/hands/<side>/<landmark> | x,y,z + rx,ry,rz | 21 landmarks × (x,y normalized image, z metres) + unit bone direction | per frame |

21 landmark order: wrist, thumb_cmc, thumb_mcp, thumb_ip, thumb_tip, index_mcp, index_pip, index_dip, index_tip, middle_mcp, middle_pip, middle_dip, middle_tip, ring_mcp, ring_pip, ring_dip, ring_tip, pinky_mcp, pinky_pip, pinky_dip, pinky_tip. <side> is left / right, classified by the wrist’s screen position.

Outputs

  • out_pop (POP) — up to 2 × 21 points with the finger-bone topology, lengths locked by rigid IK. This is the hand skeleton you render or instance onto.
  • out1 (CHOP) — tdlidar/body/hands/count, …/distance, …/frame, and the per-landmark channels for mapping and triggers.

Parameters

| par | default | what it does | |—|—|—| | OSC Port | 9000 | UDP port to listen on (match the app) | | Lock Bone Lengths | On | rigid-IK clamp so fingers keep constant length regardless of noisy Z (off = raw landmarks) | | Z Scale | 1.0 | depth multiplier; 0 = flatten the hand into the screen plane | | Aspect | auto | screen aspect ratio so the hand isn’t stretched | | Pos Scale | 1.0 | overall size of the hand in your scene | | Show Bones | On | draw finger bones (off = landmark points only) |

Quick start (beginner)

  1. In the app, enable Hands and point the rear camera at your hand.
  2. Drop the Hand op. Raise a hand — out_pop fills with a 21-point hand skeleton that follows your fingers.
  3. Wire out_pop into a Geometry COMP → Render TOP with a Line MAT to draw the finger bones.
  4. Watch tdlidar/body/hands/count on out1: 0, 1 or 2 tells you how many hands are live.

Advanced patterns

  • Particles from fingertips: select the five *_tip landmarks (thumb_tip, index_tip, …) out of out_pop into a Particle GPU / source POP, so sparks stream off each fingertip you move.
  • Per-finger curl: for one finger, take the unit bone directions (rx,ry,rz of its mcp→pip→dip segments) and feed them through a Math CHOP dot-product to measure how bent the finger is — a clean 0→1 curl value per finger, great for triggering states.
  • Heartbeat = liveness gate: because …/frame increments every frame even when the hand is dead still, compare it to its own delayed value (Lag/Logic) to know the stream is alive vs. the app paused — don’t infer “no movement” as “no data”.
  • Smooth: a Lag CHOP on out1 (or lag on the POP positions) softens tracking noise before driving anything visible.

Gotchas

  • Side is by screen position, not chirality. left/right is decided by where the wrist sits on screen, so it’s stable whether you show palm, back or edge — but it is not anatomical handedness. Don’t assume right = the person’s right hand.
  • Z is metric but noisy; X/Y normalized are the trustworthy shape. Rigid IK (Lock Bone Lengths) exists precisely so depth jitter doesn’t warp the fingers — leave it on unless you specifically want raw landmarks.
  • Data arrives every frame, even when motionless. The …/frame heartbeat means channels keep ticking; gate downstream logic on …/count, not on “did a value change”.
  • Shares the /tdlidar/body/… bucket with Body, Pinch and Gesture.