1 The idea
One track works two ways. Stabilise applies it inverted: the tracked feature stands still and the plate moves. Match-move applies it forward: an element follows the feature. Either way, a track only holds things at the same depth as the feature.
The orange-and-white warning decal was lined up on the right rock on frame 1. Change the track driving the decal, Apply as (Stabilise or Match-move) and the Reference frame, and watch the slide now and the worst over the shot. Turn on the Stabilised view to see what each track locks.
match-move: +(track(f) − track(ref)) · stabilise: −(track(f) − track(ref))2 Hands-on
Task: make the decal stick to the rock, with the worst slide over all 48 frames at most 1 px.
Start with the Stabilised view: the right track makes the right rock stand still. Then check Apply as, and the frame the decal was lined up on.
3 Deep dive
One track, two directions
A Tracker only records how far a feature moved on each frame. When you use it, you either cancel that motion (stabilise) or give it to something else (match-move).
To make an element ride with the plate it is always match-move. A stabilise applied to the element pushes it the opposite way.
| Stabilise | Match-move | |
|---|---|---|
| Track direction | Inverted | Forward |
| What stands still | The tracked feature | The element, relative to the feature |
| What moves | The whole plate | The element |
| Used for | QC a track, work on a steady picture | Stick an element to the plate |
A track only holds its own depth
When the camera moves, near things move further in frame than far things (parallax). The hill point is about 150 m away and the decal’s rock about 11 m on frame 1, so they move by different amounts.
Driving the decal with the hill track lets it slide off the rock by about 45 px on the worst frame. No reference frame fixes that, because it’s a depth difference. A very distant background behaves almost like one flat layer, so its 2D track can hold things just as far away even when the camera moves.
Before you use a track, stabilise on it: if the surface the element sits on doesn’t stand still, the track is at the wrong depth.
The reference frame has no correction
On the reference frame the transform is zero; every other frame moves relative to it. So it must be the frame you lined the element up on. Line up on frame 1 with the reference left on 24, and the element shifts away from where you put it.
Pick the reference frame first and only then export. Do the line-up on that same frame with the element’s own Transform, placed upstream of the match-move.
- 1Track a feature at the same depth
- 2Set the reference frame
- 3Transform to line up
- 4Match-move
- 5Watch the whole shot playing
Linked, baked and how many points
A linked match-move is expression-linked to the Tracker, so later track edits follow. A baked one copies the keys and doesn’t. A one-point track gives translation only; rotation and scale need two or more points.
For objects that must be rock-steady, per-frame track noise reads as jitter. Mask out anything moving in the tracked area, or use a constant offset where nothing should move.
| Type | Result |
|---|---|
| Linked | Follows later track edits |
| Baked | Copies keys, ignores later edits |
| One point | Translation only |
| Two or more points | Adds rotation and scale |
The stabilised view is a test, not the verdict
Stabilising on a track and scrubbing fast is a strict check, but here the element is resampled twice, once by the match-move and again by the stabilise, so a little edge shimmer can be resampling, not track error. Judge the final result on the normal, un-stabilised picture while it plays.
4 In real work
In Nuke
- Tracker: track a feature on the surface the element sits on, at the same depth.
- Tracker, Transform tab: go to the line-up frame and press set to current frame to make it the reference frame.
- Transform on the element: line it up on that frame, before the match-move.
- Tracker Export: choose Transform (match-move), which stays linked by expressions while the track may still change (the baked version copies the keys), then Merge (over) onto the plate.
- QC: copy the transform set to stabilise and scrub fast, then remove it; judge the result un-stabilised.
Common mistakes → the fix
- ✗ Applying the stabilise to the element✓ Elements always get the match-move; a stabilise moves them the wrong way.
- ✗ Lining up on one frame with the reference frame on another✓ Set the reference frame to the line-up frame before exporting.
- ✗ Using a far track to hold a near element✓ Track a feature at the element’s depth.
- ✗ Adding a second match-move after a roto that already rides the first✓ Mask first, then share one match-move; otherwise the motion is applied twice.
- ✗ Judging the result in the stabilised view✓ Edges jitter from double filtering; judge the final un-stabilised, in motion.
Before you send the shot
- Stabilising on the track holds the surface the element sits on still.
- The element uses match-move, not stabilise.
- The reference frame matches the line-up frame.
- Each branch has only one match-move.
- The whole shot, un-stabilised and playing, shows no slide or jitter.
5 Check yourself
The decal moves against the rock even though it uses that rock’s own track. Why?
🔒 Answer the question above and this card opens
1. Which track should drive a decal on a rock near camera?
2. You lined the element up on frame 1, but the Tracker’s reference frame is 24. What do you see?
Where the numbers come from: A 48-frame handheld shot (640×360) rendered in Blender (Cycles) through our desert set, with a green screen on a pole and a drone flying across. Frame 1 is the still plate’s camera. Every true position comes from the scene’s own 3D (truth.json, dist.f32). The tracks here are the scene’s true 2D positions (projected from Blender’s camera), so the only slide you see comes from the choice of track, direction and reference frame, not from tracking noise.