Atlas Scene Scale 📏

Every 2.5D projection scene ends up with the same two filler pieces: a ground plane and a sky card. They're the only things standing in for the hole that sky exclusion leaves behind, and their sizes are in metres - which means a set of numbers you tuned by eye on one plate is wrong on the next. The author measured it: across 31 plates, median scene distance ran from 0.95 m to 586 m. The same 50×100 m ground is a wall looming in front of one subject and a postage stamp under another.

Atlas Scene Scale 📏 is the fix for that drudgery. Feed it the scene's depth map and it measures the scene and emits support-geometry sizes in proportion to what's actually in front of the camera.

Where the numbers come from

The defaults aren't arbitrary - they're one artist's hand-tuned judgement, generalised. Someone tuned a ground by eye on a plate whose median distance was 17.0 m and arrived at 50×100 m with the plane pushed 25 m back, and a sky card at 300 m. Expressed as multiples of what the scene actually measures, that's 2.94× median for width, 5.88× for depth, −1.47× for the offset, and 1.79× the P99 depth for the sky card. The node's defaults are those ratios, so any plate - large or small - gets a plane in the same proportion. Deeper than wide on purpose: the ground exists to be travelled into.

Note it measures the depth map, not geometry. Primitives carry dimensions and a transform but no vertices; the depth map is per-pixel forward distance, which is what "how far away is this scene" actually means. And if your depth is non-metric (a relative estimator), it's reported and still used - the ratios stay right even when the metres are arbitrary, and a plane in the right proportion to a scene of unknown scale is exactly as useful as that scene is.

The inputs that matter

• depth - required, an ATLAS_DEPTH_MAP. Everything else is optional.

The five multiplier knobs (ground_width_x, ground_depth_x, ground_offset_x, sky_distance_x) are the tuning surface if you don't like the defaults - each is a multiple of the scene's median or P99 distance rather than an absolute metre value, so they transfer between plates. min_spread (default 0.15) is the safety valve: it refuses to derive sizes when the scene has less relative depth spread than that, because a failed solve parks everything at one distance and a "median" taken from that is a confident number describing nothing. Set it to 0 only if you really want numbers regardless.

The outputs

Seven sockets: ground_width_m, ground_depth_m, ground_offset_z, sky_distance_m - the sizes you'd feed a ground-plane / sky-card builder - plus median_m and p99_m so you can see what the scene actually measured, and a report string. Wire those first four into whatever node builds the primitives (the plane and card), or read them off the report and dial the numbers in yourself.

Installing

It's a small node inside the bigger atlas-camera pack:

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

Restart ComfyUI, and it shows under the Atlas menu in the orient-and-scale tier. No extra dependencies for this node - the depth map feeding it comes from whatever depth node you already run, and the maths here is pure numpy.

Gotchas

Garbage in, confident-looking numbers out. The min_spread guard is your friend - if your depth solve failed or your plate is a wall of one distance, the node will refuse rather than hand you a median-based plane that means nothing. That refusal is a feature; don't paper over it by zeroing the threshold. And remember the output is scene scale, not a finished scene - you still have to build the plane and card with those numbers and project your plate onto them.