Filter node
Gaussian Blur
GPU-accelerated Gaussian blur post-process filter. Apply a soft, natural-looking blur to any generator image with configurable radius, multiple iterations for stronger blur, quality scaling for performance, and edge mode control. This is a separable two-pass blur (horizontal then vertical) that operates on premultiplied alpha to prevent dark halo artifacts.
Inputs
| Port | Type | Default |
|---|---|---|
| EnableOff clears the output image rather than passing the source through, so the canvas shows nothing from this branch. | bool | true |
| ImageThe image to blur. Cable it from any generator or another image filter. | image | — |
| WidthSource width in Grafit units, used to size the blurred quad. Normally cabled straight from the source node's Width output. | float | 2.0 |
| HeightSource height in Grafit units, used to size the blurred quad. Normally cabled straight from the source node's Height output. | float | 2.0 |
| RadiusBlur amount in Grafit units; 0 passes the image through untouched and negatives are treated as 0. Very large values stop softening further once the kernel reaches its size cap — raise Iterations or lower Quality instead. | float | 0.02 |
| IterationsHow many times the blur is repeated, compounding into a much wider, softer falloff. Clamped to 1…5. | int | 1 |
| CropOn keeps the original image size and cuts the blur off at its edges. Off grows the output by the blur diameter so the whole soft falloff stays visible. | bool | false |
| Edge ModeHow the blur treats the image border: Transparent fades edges out naturally, Clamp extends the edge pixels so the border stays solid. Anything other than Clamp behaves as Transparent. | int | 0 |
| QualityResolution the blur is computed at, from full down to a sixty-fourth. Clamped to 0…6 — lower resolution is dramatically faster and, for big soft blurs, looks nearly identical. | int | 0 |
Outputs
| Port | Type |
|---|---|
| ImageThe image to blur. Cable it from any generator or another image filter. | image |
| WidthSource width in Grafit units, used to size the blurred quad. Normally cabled straight from the source node's Width output. | float |
| HeightSource height in Grafit units, used to size the blurred quad. Normally cabled straight from the source node's Height output. | float |
Live Preview
Interactive — Blur radius sweeping
Pipeline
The Gaussian Blur node is a filter node — it sits between a generator and a Canvas:
Generator (e.g. Circle 2D) --> Gaussian Blur --> Canvas
Image, Width, Height Image, Width, Height ImageConnect all three outputs (Image, Width, Height) from the source generator to the blur's inputs, then connect the blur's three outputs to a Canvas node.
Edge Modes
| Value | Name | Behavior |
|---|---|---|
| 0 | Transparent | Pixels beyond the image edge are treated as transparent (RGBA = 0). The blur naturally fades to transparency at the edges. This is the default and works best for isolated shapes. |
| 1 | Clamp | Pixels beyond the edge repeat the nearest edge pixel. Prevents the blur from fading out, which is useful for backgrounds, tiles, or full-screen effects where you want the blur to extend seamlessly. |
Quality Levels
Quality reduces the internal rendering resolution for significant performance gains with large blur radii. The image is downscaled before blurring and upscaled afterward.
| Value | Name | Resolution | Performance |
|---|---|---|---|
| 0 | Full (1/1) | Native resolution | Best quality, highest cost |
| 1 | Half (1/2) | 50% resolution | Good balance for medium blur |
| 2 | Quarter (1/4) | 25% resolution | Good for large blur radii |
| 3 | Eighth (1/8) | 12.5% resolution | Fast, soft look |
| 4 | 1/16 | 6.25% resolution | Very fast, heavily softened |
| 5 | 1/32 | 3.125% resolution | Extreme softening |
| 6 | 1/64 | 1.5625% resolution | Maximum performance, minimal detail |
Lower quality settings are especially effective when combined with large radii — the downscaling itself contributes to the blur effect, so you can use fewer iterations and a smaller radius at lower quality to achieve a similar visual result much faster.
How It Works
- Separable passes — The 2D Gaussian kernel is decomposed into two 1D passes (horizontal, then vertical), reducing computational complexity from O(r^2) to O(2r) per pixel.
- Premultiplied alpha — The blur operates on premultiplied alpha data throughout, which prevents dark halos around transparent edges. This is consistent with Grafit's rendering pipeline.
- Iteration compounding — Each iteration applies the full two-pass blur again. N iterations with radius r produce an effective blur approximately equivalent to a single pass with radius r x sqrt(N).
- Dimension expansion — When Crop is off, the output dimensions grow by 2x radius on each side so the Canvas quad is large enough to display the full blur falloff without clipping.
- Zero radius bypass — When Radius is 0, the blur is bypassed entirely (blit copy) for zero GPU cost.
Use Cases
- Soft shadows — Apply a blur to a dark-colored shape offset slightly from the main element to create a diffused shadow. (Note: Generator nodes with built-in Shadow support use a dedicated shadow post-processor, but Gaussian Blur gives you manual control.)
- Depth-of-field — Blur background elements more than foreground elements to simulate camera depth-of-field.
- Glow effects — Blur a bright shape and composite it over the original using Canvas blend modes for a bloom/glow effect.
- Background softening — Blur a full-screen image or video to create a soft, frosted-glass backdrop.
- Signal smoothing visualization — Blur a waveform or spectrum texture for a smoother visual presentation.
- UI element backgrounds — Create a blurred background layer behind UI text overlays for improved readability.
Tips
- Start with Radius 0.02 and 1 iteration. Increase Radius for a wider blur; add Iterations for a stronger, smoother result.
- For very large blurs, reduce Quality to 2 or 3 and increase Radius rather than using many iterations at full resolution — the visual result is similar but performance is dramatically better.
- The Crop toggle is useful when you need the output to tile seamlessly or match the exact input dimensions.
- Edge Mode Clamp is essential for full-screen effects — Transparent mode would introduce dark/transparent edges.
- Iterations are clamped to a maximum of 5. If you need even more blur, increase the Radius or lower the Quality instead.
- Chain multiple Gaussian Blur nodes for multi-stage effects (e.g. a tight blur followed by a wide bloom).
Open Gaussian Blur in the interactive catalog →
Gaussian Blur is one of 381 nodes in Grafit Pro.
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