Atlas Scope Mask 🎯

AtlasScopeMask is where the pack's 2.5D matte-painting layer stack decides what a layer is not allowed to cover. In the Atlas model, each depth band gets a projection layer, and each layer needs to know which pixels belong to other layers so it doesn't paint over them. The sky is the permanent exclusion - that's the sky_mask you're required to wire in, and it's the always-on base of every fallback. The scope part is the extra exclusions: for a given band, you can prompt for the content that should be carved out of it.

The name tells you the game. This isn't a segmenter - it's a combiner and decision-maker that turns "the base exclusion" plus "whatever this band's content is" into one clean exclude_mask, with sensible fallbacks when the content detector can't find what you asked for.

How the fallback ladder works

The inputs read like a decision tree, and that's intentional:

1. sky_mask (required) - the always-on base. Every fallback path returns exactly this.
2. prompt + segment_mask - the SAM3 segment for this band's content. The neat bit: this is lazy. Empty prompt means the layer is unscoped/absent, the node returns the sky mask alone, and via lazy evaluation the segmenter never runs. Wire the prompt and the segment gets evaluated.
3. fallback_mask - the geometry-prior fallback, tried before giving up: wire an AtlasSemanticMask here. Its fixed ADE20K vocabulary can't miss the way free text can, so it's the reliable second opinion. Also lazy - only evaluated on an actual no-match.
4. min_coverage_pct - if the segment covers less than this % of the frame, the prompt is treated as a NO-MATCH, and instead of excluding the whole layer you fall back to band-only.

Round it out with grow_px (dilate the segment before inverting - the classic GrowMask-16 default, so silhouettes don't clip) and you get the full picture.

Outputs

exclude_mask (MASK) - what this layer must not project onto - and a status string telling you which path it took (scoped, no-match + fallback, or band-only). That status output is the quiet hero: when a layer mysteriously eats the sky, the status tells you the scope prompt no-matched and what it fell back to.

The honest gotcha

The failure mode to watch is a too-loose prompt producing a too-big exclusion: prompt "building" for a band that's mostly facade and the segment covers 60% of the frame, which is real, and your foreground layer suddenly has a building-shaped hole it never should have. min_coverage_pct guards against misses, not overreaches - so scope prompts should name the thing you want to remove from the layer, narrowly, not the whole layer's subject.

Install

Pure logic node - core tier, no models, no deps beyond the pack:

cd <ComfyUI>/custom_nodes
git clone https://github.com/mikejamesvfx/atlas-camera.git

Restart, or install via ComfyUI Manager ("atlas-camera"). It lives in Atlas/04 · Masks. The masks you feed it come from AtlasSAM3Mask or AtlasSemanticMask, which carry their own install notes.