Vari Blur Node

Unlike the classic Blur, which applies a uniform strength, Vari Blur allows a different strength per pixel. The strength map comes from a second image connected to the dedicated input (a painted gradient, the Z-depth of a 3D render, a gradient mask, etc.).

Similar in principle to Depth Blur, but with a different method that often gives cleaner results (fewer artifacts at the transitions between sharp and blurred areas).

• Effects Library: Tools > Blur > Vari Blur
• Quick add: right-click in the Node Editor → Add Tool > Blur > Vari Blur

• Input (gold/orange) - required. The image to blur.
• Blur Image (green) - required. The grayscale blur map. Each pixel drives the blur strength at the matching pixel of the Input. It can be splines, text, a still image or video. You then pick the channel (R, G, B, Alpha or Luma).
• Effect Mask (blue) - optional. Limits the Vari Blur to an area. Applied after processing.

Example with a painted gradient as the blur map:

MediaIn (image) ──→ Input
Background (B&W gradient) ──→ Blur Image
                     → Vari Blur → Merge 2D → Saver

Example with the Z-depth of a 3D render:

Loader (plate) ──→ Input
Loader (Z pass) ──→ Blur Image (R or Luma channel)
              → Vari Blur → Saver

Method (default: Multi-box)

Blur algorithm (see the dedicated section).

Quality (1-10, default: 4)

Quality/speed trade-off:

• Quality 1 - fast Box blur. Preview.
• Quality 2 - enough for small radii.
• Quality 4 (default) - fits most uses.
• Quality 10+ - ultra-clean final render, slower.

Blur Channel

The channel of the Blur Image that drives the blur. Typically:

• Red / Green / Blue - for a color blur map where one channel encodes the blur.
• Alpha - for a mask with an alpha channel.
• Luminance - if the blur map is grayscale (the standard case).

Lock X/Y (default: checked)

Links the two blur axes. Unchecking it reveals two independent Blur Size X/Y sliders.

Blur Size

Global multiplier of the blur strength. The blur map drives the relative strength per pixel; Blur Size drives the absolute strength.

Blur Limit

Limits the usable range of the blur map. See the dedicated section.

Soften

Progresses Box → Bartlett triangle → Smooth depending on the Quality. Better detail preservation in lightly blurred areas. Choose it when the balance between sharp and blurred areas must stay gradual without artifacts.

Multi-box (default)

A progression similar to Soften but with a faster Gaussian approximation. A good default compromise - clean and relatively fast.

Defocus

Produces flat, circular blur shapes that approach a real optical defocus. The one to use for a realistic fake DOF with a visible aperture shape. Slower but more photorealistic.

Rule: Multi-box by default. Defocus for a photorealistic fake DOF. Soften for very gradual transitions.

When you drive Vari Blur with a raw Z-depth from a 3D renderer, the values can be huge (1000+) or infinite on pixels outside the scene. Without a limit, the blur computes absurd values (which stall the render or produce artifacts).

The Blur Limit parameter caps the values read from the blur map. Common practice: set the Blur Limit to match the maximum "interesting" distance of the scene - anything farther is clipped to that value and gets the maximum blur.

Always enable it when the blur map is a 3D Z-depth. It is unnecessary if the map is a normalized 8-bit gradient [0, 1].

• Fake DOF from a Z-depth - use case #1. Z pass from the Renderer 3D → Blur Image of the Vari Blur. Result: a DOF computed in 2D without re-rendering.
• Blurred vignette - a radial gradient (black in the center, white at the edges) as the blur map → everything around the edges blurs gradually. A classic cinematic look.
• Targeted transition - hand-paint a gradient mask to blur only a precise part of the image (top corner, the background of a pattern).
• Fake tilt-shift - a horizontal gradient (black in the center, white at the top/bottom) as the blur map → the classic miniature effect.
• Progressive dreamy effect - an animated FastNoise as the blur map → areas that move in and out of focus in real time.
• Simulating a degraded lens defocus - a blur map that simulates a lens aberration with more blur toward the edges (spherical aberration).

• The blur map sets the proportions - Blur Size works as a global multiplier. Most of the tuning is done by modifying the blur map (saturation, curves, gain) rather than touching Blur Size.
• The right channel - for a 16/32-bit Z-depth, use the R channel (Z-depths are often stored in Red only). For a painted gradient, Luminance works everywhere.
• Quality 4 for preview, Quality 8-10 for the final render. The visual difference on a final render can be worth the extra render time.
• For a truly photorealistic DOF, prefer the standalone Defocus with a Z map, or use the DOF built into the Renderer 3D if you are still in the 3D scene.
• Blur Limit should always be set if the map comes from a raw Z-depth, otherwise expect surprises on pixels at infinite distance (sky, background).
• To test a DOF placement, try a simple blur map (horizontal gradient) before moving to a real Z-depth - faster to iterate.