Apple Pencil — tdlidar_pencil

Brush a TouchDesigner parameter with real pen pressure and tilt — draw weight and angle straight into your visuals.

Category: Touch & Input · Tier: Free · Needs: iPad + Apple Pencil

What it does

Streams the Apple Pencil’s position on the iPad screen plus its pressure, tilt and the direction it’s pointing, and fires a flag when you double-tap the barrel. Pressure makes a natural fader (press harder = more), tilt gives you a second analogue axis from the same hand, and azimuth is the compass direction the pen leans. It’s the most expressive single input in the family because one stroke carries position, weight and angle at once.

OSC in

| address | type | range | rate | |—|—|—|—| | /tdlidar/pencil/x | float | 0–1 normalized screen X | pen rate | | /tdlidar/pencil/y | float | 0–1 normalized screen Y | pen rate | | /tdlidar/pencil/pressure | float | 0–1 press force | pen rate | | /tdlidar/pencil/tilt | float | pen tilt angle | pen rate | | /tdlidar/pencil/azimuth | float | lean direction (radians) | pen rate | | /tdlidar/pencil/barreltap | float | double-tap flag (momentary) | on tap |

Outputs

out1 (CHOP) — channels named after the addresses without the leading slash: tdlidar/pencil/x, …/y, …/pressure, …/tilt, …/azimuth, …/barreltap. The op grabs /tdlidar/pencil/* generically, so whichever of these the app emits will appear.

Parameters

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

Quick start (beginner)

  1. On an iPad with a paired Pencil, enable Apple Pencil in the TDLiDAR app.
  2. Drop the Apple Pencil op. Touch the Pencil to the screen and watch out1 light up.
  3. Press harder and softer — tdlidar/pencil/pressure swings 0→1. Export it onto a Blur size, a line width, or an emission rate for an instant pressure brush.
  4. Add tdlidar/pencil/x / …/y onto a Geo COMP Translate to position the brush as you draw.

Advanced patterns

  • Two-axis brush: map pressure to one parameter and tilt to another (e.g. pressure → opacity, tilt → hue) so a single stroke paints with weight and angle.
  • Direction from azimuth: azimuth is radians — a Math CHOP ×57.2958 gives degrees you can feed into a rotate, so the pen’s lean steers a streak or comb direction.
  • Barrel-tap as a mode switch: Trigger CHOP on barreltap → Count CHOP to cycle a Switch TOP between brush presets, hands stay on the pen.
  • Stroke smoothing: a Filter CHOP on X/Y gives clean vector strokes; pair with a Slope CHOP to derive stroke speed for speed-reactive thickness.

Gotchas

  • iPad + Pencil only — on an iPhone these channels never appear.
  • App support for Pencil may be partial; the tox deliberately grabs /tdlidar/pencil/* generically, so you’ll see exactly the channels the app currently emits and no error for the missing ones. Check out1’s channel list to confirm what’s live.
  • barreltap is momentary (a brief 1 then back to 0) — always route it through a Trigger/Count, don’t read it as a held state.
  • X/Y are normalized 0–1, not points; range-map before using as pixel/metric coordinates.