Split Horizontal and Vertical
Separates horizontal and vertical blur control.
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Blur & FocusBeginner
BoxBlur
Fast rectangular averaging blur
Applies a fast box filter with optional horizontal/vertical separation, channel controls, iterations and configurable border handling.
BoxBlur
DaVinci Resolve · Fusion
Applies a fast box filter with optional horizontal/vertical separation, channel controls, iterations and configurable border handling.
Overview
What BoxBlur does
Applies a fast box filter with optional horizontal/vertical separation, channel controls, iterations and configurable border handling.
Strength sets the basic blur, while Split Horizontal and Vertical lets the two axes be treated independently. That makes BoxBlur useful for quick directional softening as well as ordinary technical blur.
Iterations and Border Type matter once the blur becomes large. Replicate, Reflect and Wrap-Around avoid the dark frame edges that Black can introduce when the filter samples beyond the image boundary.
Mental model
Imagine averaging every pixel with a rectangular neighborhood. More strength or more iterations widens and softens that neighborhood.
Common uses
Quick background blur
Soften technical mattes
Pre-blur before edge detection
Smooth alpha channels
Create inexpensive utility blur passes
Flow anatomy
Inputs & outputs
The port structure shows how this node fits into a Fusion graph.
Input
Source image to process.
Effect Mask
Optional mask that limits the effect to selected areas.
BoxBlur
Fusion node
Output
Processed image.
Inspector
Important parameters
Start with these controls before reaching for more complicated workarounds.
Strength
Controls overall blur size.
Horizontal Channel Adjustment
Chooses which RGB and alpha channels participate in the horizontal blur.
Vertical Channel Adjustment
Chooses which RGB and alpha channels participate in the vertical blur.
Red
Adjusts the red channel.
Use channel-specific controls when the operation should not affect all components equally.
Green
Adjusts the green channel.
Use channel-specific controls when the operation should not affect all components equally.
Blue
Adjusts the blue channel.
Use channel-specific controls when the operation should not affect all components equally.
Alpha
Adjusts the alpha channel.
Use channel-specific controls when the operation should not affect all components equally.
Number of Iterations
Repeats the box filter for a smoother result.
Border Type
Defines how pixels beyond the frame edge are generated.
Reflect or Replicate usually avoids dark edge contamination better than Black.
Practical setup
A reliable workflow
- 1
Connect the image or matte.
- 2
Set a modest Strength.
- 3
Enable split axes only if directional control is useful.
- 4
Increase iterations for a softer technical result.
- 5
Choose a Border Type that does not introduce unwanted edge artifacts.
Typical node chain
Input→
BoxBlur→
Output
Examples
Where this node fits in real work
Matte softening
Smooth a hard mask before matte processing.
BitmapBoxBlurMatteControl
Preprocess for edge extraction
Reduce fine noise before EdgeDetect.
MediaInBoxBlurEdgeDetect
Troubleshooting
Common mistakes
Using Black borders and creating dark edges
Over-blurring a matte and losing shape
Forgetting Alpha channel behavior
Using BoxBlur when an optical bokeh look is required
Production notes
Practical tips
BoxBlur is excellent for utility masks because it is cheap and predictable.
Several mild iterations often look better than one extreme pass.
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