Small colored dots or marks placed on green screens, sets, or actors to provide reference points for motion tracking in visual effects – enable software to calculate camera movement, object position, and 3D space reconstruction for CGI integration.
What are Tracking Dots?
Tracking Dots are small markers on greenscreens, sets, or actors that serve as reference points for VFX software. They enable precise motion tracking and the correct placement of CGI elements in the image.
Basic Principle
| Aspect | Description |
|---|---|
| Definition | Visual reference points |
| Purpose | Motion tracking |
| Material | Stickers, tape, paint |
| Removal | In post-production |
Types
| Type | Usage |
|---|---|
| Screen Markers | On greenscreen |
| Set Markers | On set/props |
| Body Markers | On actors |
| Floor Markers | On the floor |
Characteristics
| Characteristic | Requirement |
|---|---|
| Color | High contrast |
| Size | Field of view dependent |
| Shape | Mostly round/cross-shaped |
| Matte | Non-reflective |
Greenscreen Dots
| Aspect | Specification |
|---|---|
| Color | Red, blue, yellow |
| Size | 2-5 cm diameter |
| Spacing | Regular grid |
| Number | At least 8-12 visible |
Placement
| Factor | Consideration |
|---|---|
| Framing | Enough dots in the frame |
| Depth | Different Z-planes |
| Distribution | Not too regular |
| Edges | Cover frame boundaries |
Material Options
| Material | Pros/Cons |
|---|---|
| Stickers | Fast, reusable |
| Gaffer Tape | Flexible, adaptable |
| Tennis Balls | Wide shots, half balls |
| LED Dots | Visible in low light |
Color by Background
| Background | Dot Color |
|---|---|
| Green | Red, orange, blue |
| Blue | Red, orange, yellow |
| Black | White, reflective |
| White Set | Black |
Size Calculation
| Focal Length | Dot Size |
|---|---|
| Wide Angle | Smaller |
| Normal | Standard |
| Telephoto | Larger |
| Close-up | Very large |
Tracking Software
| Software | Tracking Method |
|---|---|
| PFTrack | Feature-based |
| SynthEyes | Automatic + manual |
| Nuke | 2D/3D Tracking |
| After Effects | Point tracking |
Best Practices Placement
| Rule | Reason |
|---|---|
| Not on subject | Easier to remove |
| Irregular | No confusion |
| Different sizes | For depth information |
| Redundancy | In case some are occluded |
Removal in Post
| Method | Effort |
|---|---|
| Keying | With greenscreen |
| Paint | Manual |
| Clone | Duplicate area |
| AI Tools | Automatic |
Challenges
| Problem | Solution |
|---|---|
| Occlusion | Place more dots |
| Motion Blur | Larger dots |
| Reflection | Matte surface |
| Shadows | Adjust lighting |
On-Set Responsibility
| Person | Task |
|---|---|
| VFX Supervisor | Planning |
| Set Dec | Placement |
| Camera | Check visibility |
| Data Wrangler | Documentation |
Documentation
| Element | Record |
|---|---|
| Layout | Sketch of positions |
| Distances | For 3D reconstruction |
| Reference Photos | Before/after |
| Notes | For VFX team |
Today
Tracking dots remain a fundamental tool for VFX work, even as markerless tracking technologies advance. The combination of physical markers and software-based feature tracking yields the most reliable results. Careful planning and placement on set remain crucial for an efficient VFX workflow.
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