1 The idea
You don’t paint the chest markers frame by frame. Paint one clean frame, hold it (FrameHold), and let the track carry the patch through the shot. Here the patch is already painted on frame 12.
Switch “Patch follows” from “Nothing” to a track, set the tracker’s reference frame, and watch “Worst frame” and the per-frame bars under the picture. The camera rolls about 5.6 degrees and pushes in until the chest is about 13% bigger, so keep an eye on the ends of the shot.
M(f) = T(f) · T(ref)⁻¹, so M(ref) = identity2 Hands-on
Make the frame-12 patch hide the markers on every frame: worst frame under 10% marker left
Read the bars (red = still failing). If every frame is off, even the painted one, look at the reference frame. If the middle is fine but the ends slip, ask whether this track captures the whole move.
3 Deep dive
Paint once, use it for the whole shot
Painting every frame is slow, and each frame comes out slightly different, so the fix boils when played. The usual answer is a still-frame patch: hold one frame, paint it clean, and let the track move the patch through the shot.
There are only a few steps, and each has a reason. Denoising before the paint and regraining after it keeps frozen grain out of the patch.
- 1Denoise
- 2FrameHold at ref
- 3Paint the patch
- 4Match-move with the track
- 5Soft roto mask
- 6Regrain
The reference frame is where the track is zero
A match-move measures motion relative to the reference frame. On that frame the transform is identity: it moves nothing, so a patch painted there sits exactly in place and is then carried to the other frames.
Paint on frame 12 with the reference frame at 0, and frame 12 gets moved by the motion between frames 0 and 12. The patch is offset from the painted frame on, and that offset follows it to every frame.
Set the tracker’s reference frame first, then hold and paint on that same frame.
One track point or two
A single track point gives position only. When the camera rolls or pushes in, the patch neither rotates nor scales with it: near frame 12 it still looks right, but it slips more the further you go. On this shot the other markers slip by up to about 8.1 px at the ends.
Tracking markers are made to be tracked: high contrast and small, here about 15 px across, so they make good track points themselves. Track them on the original plate, before they are painted out.
| Track | What it captures | On this shot |
|---|---|---|
| 1 point (move only) | Position | Fine in the middle, slips at the ends |
| 2 or more points | Position, rotation and scale | Follows the roll and the push |
Edges, grain, and when the track dies
Mask the patch with a soft roto; a hard edge shows as a ring around it. A patch held from a grainy frame carries frozen grain, so denoise before painting and regrain so the grain changes every frame (see PC5).
If a track point leaves the frame or gets covered, the patch drifts from that frame on. Fade the fix out where the feature is gone, and scan every frame, not one still.
Play the whole shot and watch both ends: a patch usually fails furthest from the reference frame.
4 In real work
In Nuke
- Tracker: track two or more markers with T, R and S on, and set the reference frame to the frame you will paint.
- FrameHold the plate at that same reference frame (denoise first if the plate is grainy).
- RotoPaint: clone the markers out on the held frame.
- Set the Tracker to match-move, or export a Transform from it, to carry the patch through the shot.
- A soft-edged Roto as the mask → Merge (over) the patch onto the plate.
- Grain2 to regrain the patch, with the seed animated: the default seed is a constant, so the grain would freeze.
Common mistakes → the fix
- ✗ Leaving the reference frame on the first frame while painting on another✓ Set the reference frame to the frame you painted and held.
- ✗ Using a move-only track on a shot that rolls or pushes in✓ Track two or more points and use translate, rotate and scale.
- ✗ A hard-edged patch mask✓ Use a soft roto and judge the seam with a contrast-boosted viewer.
- ✗ Holding a patch taken from a grainy frame✓ Denoise before painting, then regrain so the grain changes every frame.
- ✗ Not noticing a track point leaving the frame✓ Fade the fix out where the feature is gone, and scan every frame.
Before you send the shot
- The track’s reference frame matches the painted frame.
- The track includes rotate and scale if the camera rolls or pushes.
- Every frame checked, including both ends of the shot.
- No ring at the patch edge, even with the viewer pushed.
- The grain on the patch moves every frame, not frozen.
- Track points stay in frame, or the fix is faded out where they don’t.
5 Check yourself
The patch was painted on frame 12, but the tracker’s reference frame is still 0. What happens?
🔒 Answer the question above and this card opens
1. With the 1-point track and reference frame 12, the bars are low in the middle and climb at both ends. Why?
2. One track point leaves the frame mid-shot. What happens to the patch, and what do you do?
Where the numbers come from: 24 frames rendered in Blender from our own handheld 50 mm camera move around the standing robot, with and without markers. Track data are the markers’ exact projected centres from Blender (a perfect tracker; real trackers add jitter), the painted patch is the clean render of frame 12, move, rotate and scale are 2D similarity transforms computed in your browser, and “marker left” and its limit are our own teaching measure.