Create Simple Mask

Sometimes you don't need a fancy region layout, you just need a plain MASK of a known size at a known strength to start from. That's this node. Create Simple Mask makes a solid, full-canvas mask at whatever Width and Height you give it, at an intensity you set. Nothing clever - and that's the point.

It's part of the Mask group in ComfyUI_Mira, mirabarukaso's regional-conditioning toolkit. Where Create Tilling PNG Mask and Create Nested PNG Mask carve the canvas into pieces, this one is the blank slate: a single uniform mask you can use as a base to composite against, a solid fill for a region you'll shape with other nodes, or just a quick way to get a correctly-sized MASK into a graph without wiring up an image and thresholding it.

How it works

There's almost nothing to it, which is exactly why it's handy. You specify the mask dimensions and an Intenisity from 0 to 1, and out comes a MASK tensor filled to that value. At 1.0 it's fully solid; lower values give you a uniformly semi-transparent mask. It's a generator, not a converter - no image goes in, so you're not depending on any upstream node to produce something maskable first.

Inputs and outputs that matter

• Width / Height - the size of the mask. Match whatever you're masking against, usually your latent/generation resolution.
• Intenisity - 0 to 1. Set it to 1.0 for a fully solid mask; dial it down for a weaker, uniform effect.

The single output is mask (a standard ComfyUI MASK), so it drops straight into anything that takes a mask - a conditioning node, a MaskComposite, an inpaint setup, a preview.

Worth knowing: if you need to combine several of these into one shape, the author points you at ComfyUI's built-in MaskComposite with operation add. Create Simple Mask deliberately doesn't try to do compositing itself - it makes clean building blocks and lets the standard nodes assemble them.

Installing it

ComfyUI Manager is the quick route: open Custom Nodes Manager, search ComfyUI_Mira, Install, restart. Manual install is cd ComfyUI/custom_nodes && git clone https://github.com/mirabarukaso/ComfyUI_Mira.git followed by a restart. If the pack throws an error on load, run pip install -r requirements.txt inside the folder and restart. There are no model files involved.

Common issues

Honestly there's not much to break here. The main confusion is expecting it to do more than it does - this isn't a mask-from-image or a mask-with-position node. It fills the whole canvas at one intensity. If you want a rectangle at a specific offset, or corner masks, those are different Mira nodes (the README's Create Mask With Canvas and watermark-removal masks cover positioned rectangles). If you want per-region masks for two characters, you want the tiling or nested PNG mask nodes instead.

One practical note that applies across the whole mask family: keep your mask size and your working resolution in sync. A mask that doesn't match the latent it's applied to is the usual cause of "my mask is offset or scaled weird," and since this node takes explicit Width/Height, it's easy to leave a stale value in there when you change generation size. Wire the dimensions from the same source that drives your canvas and you'll avoid it.