Background Subtract
Updated: 8 Sep 2025
TBC
Background Subtract
Method #
This node …
Parameters
Parameter Details Preview In Viewport
Preview the generated image as an overlay in the viewport.
Apply PostFX Before Alpha Image Input (Legacy)
When enabled, the alpha input image is applied after the postfx pass, overwriting any effects the postfx would have applied to the alpha channel.
Legacy Effect Mask Blend
Blend input masks using the legacy behaviour kept for pre-2022 scenes. Leave disabled for new compositions.
Difference Tolerance
How different a pixel must be from the background plate before it counts as foreground.
History Update Rate
How quickly the learned background plate absorbs new frames. Higher rates adapt faster to scene change, lower rates hold the reference longer.
Visualise History Buffer
Display the current background plate used for comparison, instead of the segmentation result.
The properties control the time at which the node is active. See Timeline for editing time segments.
Parameter Details Duration
Control the duration of the node’s time segment.
- Composition Duration : Use the length of the composition for the node’s time segment duration.
- Custom : Set a custom duration for the node’s time segment.
Node Time
The custom start and end time for the node.
Duration (Timecode)
The length of the node’s time segment (in time).
Duration (Frames)
The length of the node’s time segment (in frames).
Time Segment Enabled
Set whether the node’s time segment is enabled or not in the Timeline.
Inputs
| Parameter | Details |
|---|---|
| Preview In Viewport | Preview the generated image as an overlay in the viewport. |
| Apply PostFX Before Alpha Image Input (Legacy) | When enabled, the alpha input image is applied after the postfx pass, overwriting any effects the postfx would have applied to the alpha channel. |
| Legacy Effect Mask Blend | Blend input masks using the legacy behaviour kept for pre-2022 scenes. Leave disabled for new compositions. |
| Difference Tolerance | How different a pixel must be from the background plate before it counts as foreground. |
| History Update Rate | How quickly the learned background plate absorbs new frames. Higher rates adapt faster to scene change, lower rates hold the reference longer. |
| Visualise History Buffer | Display the current background plate used for comparison, instead of the segmentation result. |
The properties control the time at which the node is active. See Timeline for editing time segments.
| Parameter | Details |
|---|---|
| Duration |
Control the duration of the node’s time segment.
|
| Node Time | The custom start and end time for the node. |
| Duration (Timecode) | The length of the node’s time segment (in time). |
| Duration (Frames) | The length of the node’s time segment (in frames). |
| Time Segment Enabled | Set whether the node’s time segment is enabled or not in the Timeline. |
| Name | Description | Typical Input |
|---|---|---|
| Effect Mask | Mask out areas that Post-FX applied to this node won’t be applied. | Video Loader |
| Alpha Image | Use a separate video nodes luminance values to overwrite the alpha channel of the image. | Video Loader |
| Parameter Value Array | Used to set the parameters of the node using an array. | Parameter Array |