The club is only as findable as the room.
A golf shaft is a dark quarter-inch stick moving past 100 mph — the hardest thing in the bay to track. What decides how well we track it isn't really the algorithm; it's the room it's swung in. A bright bay with a plain wall gives up the whole swing arc; a dark sim room hides half of it. And where the room can't help, a few grams of retroreflective tape on the shaft — lit by a small ring at the lens — lift club tracking to instrument grade. But tape changes a club's swing weight, so the bare shaft had to get there too — and it has: a plain steel shaft is now read as its own ruler, in the shipping pipeline and on by default, and against a hand-drawn mark it matches the taped club. Dark graphite — drivers, fairway woods, hybrids and black-graphite iron shafts — is the case that keeps tape in the job.
Club and ball tracking now runs in the analysis pipeline, on by default — this page explains the method behind it. The numbers are produced, not yet signed off: every part of it is still being measured against a hand-annotated corpus of real swings before anything is released. See how we earn the numbers →
The room does half the work
Before any code runs, the room has already decided how easy the club is to see. It's your choice — nobody should repaint a wall or bin a sim room to use a camera — but two things matter here, and they aren't equal.
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Light is the hard limit
Missing photons can't be recovered in software. A dark room forces long exposures (more blur) and high gain (more noise), and the shaft either vanishes into dark surrounds or washes out against a bright mat. No detector fixes that after the fact.
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A quiet background is second
Static clutter — window frames, screens, club racks — invites false locks, but it's manageable: the tracker can veto anything that was already sitting in the empty scene. Manageable isn't free, but unlike darkness it isn't a wall.
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An honest ladder
Best to worst: bright light and a plain wall (full performance), bright but busy, dark but plain, and — the typical home simulator — dark and busy. That last one is the hard case, and it's exactly where tape earns its place.
The point of the tape. The retroreflective option below is deliberately environment-independent — it makes the hardest room behave like the ideal one. That's why it's the right answer for a black sim room, and largely unnecessary in a bright bay with a quiet backdrop.
Illustrative — light first, background second; tape lifts tier 4 to tier 1.
A few grams of tape, instrument grade
Vision-only tracking is the default, and no one has to touch their clubs. But a hard room takes its toll on any photometric detector long before it troubles a marker — and a black graphite shaft is a hard room all by itself. For a dark bay, or for the driver, woods and hybrids in any bag, a taped shaft changes the problem entirely.
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Bands become bright blobs
Retroreflective tape lit by a small light at the lens throws that light straight back, saturating as bright, compact dots whatever the background — dark wall or blown-out mat alike. A banded shaft is trackable exactly where a plain one is invisible.
- ✓
Known spacing is geometry
Bands at measured spacings turn every frame into direct geometry: projected spacing against known spacing gives the shaft's foreshortening outright, the line of bands gives its angle without leaning on the hands, and the clubhead follows as a known extrapolation even when the head can't be seen.
- ✓
A pattern, not a lucky flash
Along-shaft distance ratios survive projection, so the pattern reads the same at any club angle. A specular glint is one blob; several bands in a line at the recorded ratios are unmistakably ours — and because blur smears across the shaft while the gaps run along it, the pattern survives the impact streak.
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One physical rule
Retro tape returns light to its source within a ~1–2° cone, so the light must sit at the lens — a small LED ring, not the ceiling. Visible-band only; never IR, which fights launch monitors.
Optional by design — and getting more so. The untaped tracker stays the product, and every taped swing doubles as dense ground truth for proving the unmarked detector, so both improve together. Taping is an opt-in high-accuracy mode — never a requirement — and on a bare steel shaft's angle the untaped club now stands on its own. Where it still earns its keep is the graphite end of the bag: a matte black shaft gives the unmarked reader neither the brightness nor the grip-end transition it works from, so drivers, fairway woods, hybrids and black-graphite iron shafts are the clubs worth taping. What a bare club gives you → · How to mark up a club →
Illustrative — a “2–1–3” band pattern, lit from the lens and read as geometry.
A bare shaft is its own ruler
Tape works — but six bands of glass bead on a shaft change the club's swing weight, and a club whose swing weight has changed produces a different swing. That makes the measuring instrument part of what's being measured. So the tape had to become optional in fact, not just in principle — and for a steel shaft it is: a plain iron off the rack now goes through the same stack, with nothing stuck to it.
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The tape was never what made the shaft bright
Measured on the same iron, the same rig and the same exposure: bare steel between the bands saturates the sensor at address and through the lit downswing exactly as the bands do, and even in the dark arc at the top of the backswing it still reads 35–90 grey levels over a background of 6–8. What the tape uniquely supplied was never contrast — it was metric geometry.
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Two landmarks replace six bands
A bare shaft carries its own marks at known millimetre positions: the grip end, where black rubber becomes bright steel, and the ferrule and hosel at the far end. Two landmarks at recorded distances pin down exactly the two unknowns the bands used to give — how many pixels a millimetre is worth in this frame, and how far up the shaft the hands are — with no which-way-round ambiguity, because the grip end is the one near the hands.
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A lock is a lock
What comes out is fed to the tracker at exactly the point the tape's answer was: the same hard anchor for the global solve, the same confidence tier, the same right to publish an address frame or a held finish where the club is barely moving. A taped club still uses its tape — it just stops being the only route to a measured frame.
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Where steel ends, tape starts
Both landmarks are steel facts: the grip end works because black rubber meets bright metal, and the brightness above is the shaft itself returning light. A matte black graphite shaft gives neither — no transition to find, and a shaft that reads as dark as the room behind it. So the driver, the fairway woods, the hybrids and any black-graphite iron shafts stay tape's territory; steel irons and wedges no longer need it. A bag can be mixed — the tracker is told per club, and takes whichever route that club offers. Taping a graphite shaft →
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What you have to tell it
Three numbers per club, taken once with a tape measure: the exposed shaft from the bottom of the grip to the top of the hosel, the hosel's distance from the butt, and where your hands end on the grip. That's the whole setup cost of an unmarked club. How to measure a club →
Where it stands. Scored against hand-drawn marks on seven swings of an unmarked 6-iron, the published shaft direction sits 2.1° from the mark at the median — against 2.3° for a taped club put through the same stack, and 4.5° for that same taped club as the tracker shipped. One club, one session and one marker's hand — enough to turn the path on, not enough to call it proven. That was a steel 6-iron, and steel is what the unmarked path is measured on; graphite has not been scored at all, and tape remains the honest answer there. It now runs on by default for every club, taking the bare route where the shaft allows it; the clubhead's exact position on a bare shaft still trails the taped one, and the numbers keep being measured against the corpus like every other part of the stack. How we earn the numbers →
Illustrative — the grip end and the hosel sit at known distances; two of them are all the geometry the bands used to supply.
The fastest move in sport
Most rooms aren't the ideal bay and most clubs aren't taped — so the tracker still has to find a plain shaft in whatever light the room gives it. That's the product default, and it's a hard problem: a full swing lasts under two seconds, the downswing a fraction of that, and at those speeds an ordinary camera fights two things at once.
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Severe motion blur
Past 100 mph a thin shaft isn't a crisp line — it smears into a faint, semi-transparent wedge of grey across the frame.
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Background clutter
Alignment sticks, trouser creases, shadows and seams in the turf all look line-like — and tempt a naive tracker into "finding" a club that isn't there.
Illustrative — the club becomes a faint fan; the ground lies in wait.
How the computer looks
Rather than search the whole frame at once, the tracker works outward from what it already knows for certain.
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Anchor on the hands
It first finds the golfer's hands from the body-pose skeleton. That becomes the pivot everything else is measured from.
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Search outward in rays
It casts search lines out from the hands in a circle, only as far as a club could possibly reach.
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Look for a ridge
Along each ray it looks for a long, high-contrast run of dark pixels — the signature of a real shaft, not a stray mark.
Illustrative — rays sweep outward from the hands.
Where the naive way fails
Blind to the golfer's body, that basic search falls into two classic traps.
- ✗
Panicking when cropped
To guess scale it assumed a fixed height. Crop the feet out of frame and that guess collapses — the search widens to the whole image and gets lost in the noise.
- ✗
Locking onto tiny lines
A club is longer than an arm, yet the basic search would happily lock onto a two-inch sleeve crease or watch strap beside the hands — bright, sharp and completely wrong.
Illustrative — a crop and a crease, both leading the search astray.
Scale and gate by the arm
The fix is to tie the search to the skeleton itself. The golfer's own arm sets both how far to look and how short is too short.
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Sizing from the arm, not a guess
We measure the arm on screen, shoulder to wrist. A club is always around 1.8–2.2× that length, so the search radius is set precisely — however the video is framed or cropped.
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A physical-length gate
A club is longer than an arm, full stop. Anything shorter than one arm length is rejected outright, so sleeve folds and watch straps never reach the matching stage.
Illustrative — the arm sets both the reach and the floor.
A swing is a double pendulum
Mechanically, the lead arm and club behave like two linked pendulums. That gives a physics-based guardrail for where the club can plausibly be.
- ✓
A predictable wrist-cock angle
The angle between lead arm and club follows a known curve through the swing — near straight at address, hinged near the top, holding lag, releasing back to straight at impact.
- ✓
A moving angle guardrail
Knowing the swing phase and the arm's angle, the model predicts where the club should be, allows a soft margin around it, and rejects anything that grossly breaks the physics. Because the swing reverses direction exactly once, the rotation direction inside each phase is known — which makes a 180° flip structurally impossible rather than merely unlikely.
Illustrative — the physics narrows the search to a sector.
Solve the whole swing, not each frame
Here is the part that matters most, and the part that changed. The tracker does not decide where the club is on frame 40 and then move on to frame 41. It lays out every plausible club angle on every frame at once, and picks the single best path through all of them.
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A grid, not a guess
Each frame gets a row of candidate shaft angles, each scored by how much real evidence the image offers for it. That is the only thing the pixels are asked.
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The physics is the cost of moving
Stepping from one frame's angle to the next carries a price set by the constraints above — the club may not reverse direction mid-phase, may not exceed a plausible rotation rate, may not leave the wrist's reachable envelope. The best path is the one that explains the evidence and obeys the swing.
- 3
A bad frame costs nothing
Where the image gives up entirely, the path simply crosses the gap under those same rules — a bounded, one-directional sweep rather than a straight line drawn between two guesses. It is honest about which samples were measured and which were bridged.
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Why this replaced the old approach
The previous tracker met each false positive with another generic guard and bought its honesty by abstaining, so coverage shrank with every patch. Judging a whole path against the physics rejects counterfeits by understanding them, and keeps the real measurements it used to throw away.
Illustrative — candidates everywhere, one path chosen.
Don't fight the blur — predict it
At the bottom of the downswing the club is a ghost. So we stop hunting for a crisp line and change the rules for the high-speed zone.
- ✓
Expect a wedge, not a line
From the club's speed and the camera's exposure time, the model works out how wide the blurred fan should be — then looks for that fan instead of a sharp edge.
- ✓
Add up the faint energy
Any single pixel in the smear is too faint to trust, but summing the light across the whole predicted sweep adds up to a confident detection.
Illustrative — energy summed across the predicted sweep.
Two tracks that check each other
Because the tracker produces both a measured path and a predicted one, it can grade its own work — and show that working on replay.
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Measured vs predicted
One path comes from the pixels, the other from the physics model. The gap between them is a running health check on the tracker.
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A "ghost" overlay for testing
During checks, a faint dashed prediction can be drawn behind the solid detected club, making any drift easy to spot by eye.
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A clubhead trail on replay
Replays draw a fading, glowing trail of the last few clubhead positions, so swing path and release read at a glance.
Illustrative — measured and predicted, side by side, with the trail.
Tuned to the footage in front of it
A few touches let the tracker adapt to real, messy video rather than assuming ideal conditions.
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Exposure, measured not assumed
A quick first pass measures how wide the blur smear actually is on this footage, so the model uses the real exposure rather than a fixed default.
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Eased for unusual swings
It gauges how clean the footage is and relaxes or tightens its assumptions for non-standard stances, instead of forcing one setting on everyone.
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Handedness, worked out for you
Left- or right-handed is read once per swing from the direction the hands travel — which needs no club detection at all, and so is available before the search even starts. Nothing to set.
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Club lifted off the background
A still background is estimated and subtracted, and the moving body is masked out, so the faint club smear stands clear of everything else.
Still being proven. These refinements are built and improving, not signed off. Next on the bench: projecting the physics through the camera's true 3D geometry, calibrating against motion-sensor ground truth, and extending the model to down-the-line views — each held to the same validation bar before it ships. The constraints and the global solve, in engineering terms →
Illustrative — isolating the club from a moving scene.
The room, the tape, the physics.
Good club tracking starts with the room, leans on a few grams of tape where the room — or a black graphite shaft — can't help, and now does without it on bare steel, reading the shaft's own landmarks as geometry — while for every plain shaft in between it falls back on what a body and a swing can physically do. All of it is drawn from the literature, kept open to inspect, and held against real swings before it ships. The first beta shipped in September 2026; it's still a prototype under validation, with 1.0 targeted for late in the year.