🅐 Mask Blur

The difference between a good inpaint and a visible seam is often just a few pixels of feathering on the mask. Hard-edged masks make the model draw a harsh boundary; a softly blurred mask lets the generated content blend into the surrounding image. ACE_MaskBlur is that feathering, packaged as one node: a gaussian blur applied to a MASK, with a single radius slider.

It's part of 🅐 Ace Nodes (hay86/ComfyUI_AceNodes), the usual one-author grab-bag. It's a three-line utility - which is exactly why it's so easy to just use instead of rebuilding it every time.

How it works

Input mask, output mask. The node applies torchvision's gaussian_blur with a kernel sized from the radius. Three implementation details worth knowing:

• radius of 0 passes the mask through untouched - handy for A/B testing in a workflow without rewiring.
• Even radii get bumped up by 1. Gaussian kernels must be odd-sized, so radius = 6 silently becomes 7. Doesn't matter for results; just don't be confused when the "exact" number you typed isn't what ran.
• The blur is on a single channel (masks are 1-channel by nature), so it's fast and negligible on VRAM.

Where you'll use it

The classic spot is right before an inpainting node: mask out a region, blur it, and the inpaint blends in. Same trick applies to any compositing where you're pasting a generated region back - a feathered mask hides the paste line. It also shows up after auto-maskers (face/object detectors that produce noisy masks) as a cheap denoise - blur first, then the mask reads as a smooth gradient instead of a jagged scribble.

There's no depth here, and that's the point: it's a primitive. The only real decision is the radius - small (2–5) for a gentle edge softness, larger (10+) when you genuinely want the mask to fall off slowly across the region. Start small; over-feathering a mask makes the model treat half the image as "partially masked," which can weaken the inpaint.

Installing

ComfyUI Manager → search ComfyUI_AceNodes, or:

cd ComfyUI/custom_nodes
git clone https://github.com/hay86/ComfyUI_AceNodes

Then restart. Installing the pack pulls its heavy requirements.txt (transformers, rembg, insightface, soundfile, …), though this node only needs torch + torchvision, which ComfyUI already ships.

One honest note: every mask-focused pack has a blur node, and plenty of them add a "feather" that does the same thing. This one is fine - simple, correct, no surprises. The reason to have it specifically is that you're already in the Ace Nodes pack for one of the bigger utilities; there's no reason to install a second pack just for mask feathering.