Track Modifier

The Track modifier references a Tracker node and follows one of its tracked Patterns. The value of the target parameter (typically a 2D Position) is updated on every frame from the motion of the tracking point.

Very useful because, unlike a direct connection between two nodes, you can add tracking as a modifier on parameters that do not support a regular connection (e.g. the position of a Bitmap Mask, the Center of a Glow, etc.).

• Right-click a 2D parameter → Modify With → Track.
• Creates a Track node linked to the target parameter. Then set up the source Tracker.

Direct connection (Tracker output)

Possible when the target parameter is a visible input of the node. An explicit link that is visible in the graph.

Track modifier

For any 2D parameter of the node, even those not exposed as inputs. More universal.

Rule: if the target parameter has a connectable input and it stays readable → direct connection. Otherwise → Track modifier.

Sticker that follows a subject:
Tracker1 (tracked subject)
   ↓
Sticker.Center → Track modifier (Tracker = Tracker1, Pattern = 1)
   = the sticker automatically follows the subject

Glow centered on a tracked face:
FaceTracker (Planar Tracker) tracking the face
   ↓
Glow.Center → Track modifier (Tracker = FaceTracker)
   = the glow follows the face frame by frame

Animated bitmap mask:
Tracker.Position
   ↓
BitmapMask.Center → Track modifier
   = the mask follows the tracking

With Vector Result to split axes:
Tracker1.Position.X → Vector Result.X
Tracker2.Position.Y → Vector Result.Y
   ↓
Position → hybrid X/Y modifier from 2 trackers

Tracker

Reference to a Tracker node in the composition. Pick it from the dropdown or drag & drop the Tracker.

Pattern Index (default: 1)

If the Tracker holds several tracked patterns, choose which one to use. Classic Fusion Trackers can hold 1-4 patterns.

Offset X / Y

Offset in pixels from the tracked position. Lets you place it slightly next to the exact point (e.g. above a tracked face).

• Sticker / annotation following a subject - a label that follows an animated character. Track modifier on Center.
• Tracked Glow / Defocus - an effect centered on a moving subject, followed automatically with no manual animation.
• Animated mask - Bitmap Mask, Polygon Mask, Ellipse Mask centered on a tracked subject.
• Tracked particle emitter - a pEmitter whose Position follows a subject (sparks around a tracked magic wand).
• Combined multi-trackers - Track modifier + Vector Result = hybrid X/Y from different trackers.
• Replacing assets after tracking - once a Tracker is computed, hook several parameters to it for a tracking-based pipeline.

• The Tracker must be computed first - the Track modifier does not do the tracking itself, it reads an existing Tracker. Make sure the Tracker has properly tracked the subject.
• Pattern Index for multi-track - if a single Tracker holds several patterns, choose carefully. Pattern 1 = the first pattern defined.
• Offset for adjustments - to shift slightly (e.g. a sticker above the face), a positive Offset Y does the job.
• Can be combined with other modifiers - Track + Calculation to scale the trajectory, Track + Perturb to add shake on top of the tracking.
• Automatic update if the Tracker is re-tracked - changing a Tracker (re-tracking, adjustments) automatically affects every linked Track modifier. A non-destructive workflow.
• Prefer the Planar Tracker for surfaces - the Track modifier works with the classic Tracker but also with the Planar Tracker (which outputs Position + Rotation + Scale).
• For 3D-aware workflows, consider the Camera Tracker, whose locator points the Track modifier can also use.