Notes

How Workout Director is built

A series on the iPhone app and its backend.

• Counting reps without the video leaving the phone →

  30 Oct 2026 · Workout Director, part 1

  The camera feed never leaves the iPhone.

• Drawing exercise figures from code →

  30 Oct 2026 · Workout Director, part 2

  Every exercise figure in the app is a 3D render of one rigged body, posed from a spec, measured against pose-estimation targets and drawn as line art.

Coming next

• Choosing a pose model for the phone

  Part 3

• Most of a rep counter is the reps it doesn't count

  Part 4

• Testing counting changes before they ship

  Part 5

• A voice coach that asks before it acts

  Part 6

• A small TypeScript backend on AWS Lambda

  Part 7

• Shipping without breaking old phones

  Part 8

• What I'd do differently

  Part 9

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