How each sheet is decided

Once the depth map is cut into classes, each class has to become a sheet somebody can actually cut. That involves three decisions the studio makes for you, and this page is what they are — because when a scene comes out wrong, the reason is nearly always one of them.

Every sheet is read both ways round

A depth region can be cut as material, or its surroundings can be cut as material with the region as an opening. Neither is right in general. A tree line is a tree line as drawn; a scatter of leaves is thirty loose pieces as drawn, and one plate with thirty holes read the other way.

So every sheet is traced both ways, each version is measured as a physical piece — how many pieces would fall out, how small they are, how thin the material gets — and the one that survives the laser wins, sheet by sheet. One scene can have layer 2 inverted and layer 3 normal. The layer list says which, and hovering the polarity badge gives the numbers that decided it.

Fewer floating pieces does not win on its own. A reading that would turn a drawn silhouette into a silhouette-shaped hole, or that would lose the focal subject, is refused however cleanly it cuts. When the two readings are close, the picture as drawn is kept.

That holds for every sheet, not only the subject's own. Read inverted, a sheet in front covers everything farther away than it, so a front sheet flipped to save a few loose petals can lay a solid board over the flower behind it and leave a stack that looks flat. A sheet whose inverted reading would cover much more of the focal subject than the picture as drawn does is kept as drawn, and hovering its badge says so, with the loose pieces that costs. Earlier builds could make that flip; rebuilding such a scene, which is free, keeps the subject in view.

The same is true with no subject named at all. Read inverted, sheet 1 is every depth from 3 back as one board on the front plane: the sheets behind it can no longer be seen, and a portrait or any other picture full of soft tones comes out as a flat panel with a few holes in it. So a sheet is only inverted when that brings forward no more than the depth directly behind it - in practice the sheet second from the back, which is where a sky full of stars belongs. And a sheet is never inverted behind a sheet with loose pieces, since a loose piece is glued to the wood of the sheet behind it and the inverted reading has a hole exactly there. Both say so on the badge, with the loose pieces kept instead. A picture with a lot of loose pieces as drawn is best built with fewer Layers, or with its subject named as the Focal subject so the studio protects it.

If you disagree with the call

Generate again with that depth described as a connected silhouette — a fence with rails, a tree with a trunk to the ground, foliage in clumps rather than as a spray. The reading follows the picture, so the picture is where to fix it.

Traced from the picture, corners and all

Every sheet’s outline is an image trace of the picture itself, the way a bitmap is traced into vectors in a drawing program. The edge of a shape in a depth map is soft, a few pixels wide; the trace crosses it where the grey is halfway between the two sides, so the outline sits where a person sees the edge, to a fraction of a pixel.

A corner is wherever the outline turns sharply, and it is kept as a corner. A curve is kept as a curve, however small the circle. Nothing is smoothed along the way and nothing is added: a bat’s scalloped wing comes out scalloped, its tips where the picture put them. There is no tension or smoothing setting, because there is nothing for one to do.

One thing is put back. The picture’s own softness takes the point off a corner — a right angle loses about a pixel, a sharp tip more — and where two straight sides meet through that small arc, the arc becomes the point where the sides meet. Only there, only if both sides are straight, and never further than the softening can account for. A wing tip with curved sides is left exactly as traced. Where two corners put back like this would cross each other — on either side of a gap a few pixels wide, between two teeth say — the second is left as traced.

Before a sheet goes any further, its cut is checked against the picture it was traced from. Anywhere away from an edge they must agree on what is wood and what is open; a cut that does not is traced again, more plainly, and a sheet that still disagrees stops the build with a message rather than being cut. One crossed outline used to be enough to turn a sheet inside out — every leaf and petal inside it a hole, every gap wood — and nothing noticed.

Thin parts of a shape

The bars across a round window, the balusters of a porch, the wing of a small bat. At three or four pixels wide the picture’s soft edge blurs them to a grey between their own and the sky’s, and read pixel by pixel they used to fall into whichever depth that grey happened to land in, or vanish altogether. They now go with the thing they hang from.

Below about three pixels — half a millimetre on a 300 mm scene — a line is thinner than the picture can carry through its own softening and may still drop out. Cutting the scene larger is what keeps it.

Repair, then the stack

Whatever is still loose after that is repaired, and the rule for every repair is the same: the sheets are cut as the depth map has them, and the build report says what is loose, what is hidden and what is fine.

• Loose pieces smaller than Min feature size — compared by area, 0.25 mm² at the default — are absorbed into the openings around them, because a piece that size cannot be placed by hand. That is where a missing star or tooth has usually gone; see Every control.
• Necks of material narrower than the minimum bridge width — material holding two bodies together, which would snap in the weeding — are widened to it.
• Openings narrower than the Min cutout width are closed, the whole opening or none of it. The image model often draws a soft, darker line round a shape where the depth map should be one flat plane; read as depth, that line became a row of hairline slits round the shape, which a laser scorches rather than clears. An opening wide enough anywhere to fit a disc of the minimum width is kept exactly as drawn.
• Fine detail is not widened. The point of a pine, a blade of grass, the sliver between two branches: each is thinner than the minimum for its last few millimetres and each is held by the material behind it. Widening them turned every point in the picture into a blunt lump, so they are kept exactly as drawn and reported instead.

Only when every sheet is settled is the stack assembled and checked as a whole.

One more rule is applied as it is assembled. Where a nearer depth borders one two or more steps farther, that boundary is cut on more than one sheet — the outline of a subject standing against the sky is the edge of its own sheet and of every sheet between it and the sky. Each sheet is traced on its own, and two tracings of one edge never agree to the last hundredth of a millimetre, which in a cutting program looks like layers whose lines do not line up. So, front to back, every sheet takes the sheet in front's coordinates along each stretch the two share. The files carry one reading of every edge, and the sheets sit flush along it.

Loose pieces: cut loose, bridged or cut away

A piece of a sheet attached to nothing - the moon inside a ring of cloud, a face floating inside an Outline border - is handled one of three ways, chosen under Loose pieces in Build quality.

Cut loose, the default. The piece is cut free and reported, and you place it by hand when you glue the stack — which is what the sheet behind it is for. That is the opposite of the layer studio, and deliberately so: a mandala is one plate and a piece that comes away from it is lost, while a landscape is a stack and the sheet in front holds a loose piece exactly where the picture put it.

Automatic tabs bought nothing for that and cost the picture: long thin bars ruled across a fence or a stand of foliage, which is the first thing the eye goes to.

Add bridges is for when you would rather have the tab than the handling. An island with ground beneath it is given a stem down to it — on a landscape that reads as a trunk or a stalk rather than as a bar — and anything still loose gets the smallest tab the material holds, placed where you are least likely to notice it.

Cut away is for when you want neither: no pieces to place and no tabs. Each loose piece is taken out of its sheet, so every sheet comes off the laser as one piece. Nothing becomes a hole through the stack - each sheet is everything at its depth or nearer, so the sheets behind always have material there - but a piece loose on one sheet is usually loose on the sheets behind it too, and goes from them as well. So it falls back to the first sheet where it is joined to the frame: one sheet back when the shape behind it reaches the border, further when that floats too. With the Outline border, which follows the design, much of a design stays within a sheet or two of where it was drawn; inside a Frame border a design drawn on a page can fall all the way to the backdrop, leaving the front sheets as bare frames. The build says how much of the design moved back, and by how many sheets, and warns with cut_away_bare when a sheet is left as only its frame. Rebuilding with another choice is free, so build it both ways and compare them in the 3D view.

There can be a little overlap

Grass over the foot of the cabin, a branch across the moon. That overlap is what makes the piece read as deep, and the studio does not try to remove it. What it checks is that the sheets in front have not hidden most of what matters.

For each protected element the plan named, it measures how much still shows once every nearer sheet is on: a primary subject is expected to keep about two thirds, a secondary one about half. Below that the check says so plainly, and by default that is all it does — the sheets are cut as drawn. See destructive_occlusion for what to do about it.

Reading the layer list

Each sheet in the list shows its role, its polarity, how many pieces would have floated as drawn and how many still do after repair, and the narrowest material on it. Clicking a sheet opens it in the layer editor.

Open the Debug tab, under the sheet list, to see both readings of every sheet side by side — the rasters, the traces, the counts and the score — and the sentence that decided between them. When a scene comes out wrong and the reason is not obvious, that panel is where it is.

What each sheet in the list tells you

Every row in Sheets carries eight numbers beside its thumbnail. They are the same measurements the studio used to choose the polarity, so when you disagree with a decision they are the evidence.

• material — how much of the sheet is material rather than opening.
• min width — the narrowest material on the sheet. Red when it is a load-bearing neck under the minimum, amber when it is fine detail.
• floating — loose pieces as traced, then after repair.
• paths and nodes — how much geometry the cutter will chew through. A sheet with ten times the nodes of its neighbours is usually one with noise in the picture.
• preserved — how much of the depth region survived repair.
• focal kept — how much of the focal subject this sheet still shows. Amber under about 60%.
• bridges · stems — what the repair added, which is zero unless Add bridges is on.

Two controls above the list help you look rather than guess. The front → back / back → front toggle only changes the display order — sheet 01 is always the nearest one. The eye beside each row hides that sheet from the stacked and exploded previews, and an opacity slider on those views fades the nearer sheets so you can see what is cut behind them.

The Validation, Plan and Debug tabs

On the right, under the sheet list, are three tabs, and they are where the studio explains itself: Validation for the check, Plan for what the scene was meant to hold, and Debug for everything the build saw. There is no separate notes panel; what the build has to tell you is in these.

Plan

What the studio decided your scene contains before any picture existed: every depth with its role, the elements expected there, which are protected, and the band of the frame each depth should mostly occupy. Below that is a Must stay visible list with each protected element and its floor — about two thirds for a primary subject, about half for a secondary one.

Where the elements come from depends on the prompt:

• A prompt that lists its sheets. "Depth bands front to back: dune grass and rocks; breaking waves; the cliff and lighthouse; …", with one band per sheet, is used as written. Each sheet is its band, and the subject goes on the band that names it. Every scene template is written this way, and so can your own prompt be. If the list has more or fewer bands than Layers, or never names the Focal subject, it is not used.
• A design drawn whole. With Fit on Whole design, nothing cut off, the sheets are counted from the front (front, second, third, …). The subject goes on the farthest sheet that is cut, where the centre of a mandala or a wreath sits, and the last sheet is the plain backdrop. There is no sky and no grass, and nothing is placed by its height in the frame, because a design is seen straight on.
• Anything else. The studio uses the vocabulary of the sort of scene your prompt describes, and places nearer things lower in the frame.

Read it when a generation surprises you. The plan is derived from your prompt and it is often where the surprise started.

Validation

More than the list of findings. It also shows every protected element with a bar for how much of it survives the stack, its floor, and which sheet is covering it and by how much; a uniqueness grid saying how much of the picture each sheet carries and how similar it is to its neighbour; and a count of any occlusion repairs that ran. Every finding is clickable and takes you to the sheet it is about. See Reading the check.

Debug

Everything the build saw, and the place to go when a scene is wrong for a reason none of the above explains. It carries the number of depth classes and whether the picture was flipped, the grey window each class ended up with, the board scale in millimetres per pixel, the raw and normalised and quantised pictures side by side, and then per sheet: the band, both candidate readings, the final raster, both scores broken down term by term, the sentence that chose between them, and a line for each thing the repair did to that sheet: how many loose pieces it dropped for being under Min feature size and the largest one's area, what it left loose, what it widened.

Two sets of notes sit above and below all that. At the top, under the grey windows, are the notes about the picture itself: that it was flipped, that drop shadows were read as the surface they fall on, that the backdrop was carried out to a circle's rim. At the foot are the Build notes. They start with what the border did — a notch kept straight, a small piece left outside an Outline, a piece joined on by a bar of frame, a picture whose outline is simply its rectangle — then say what is hidden, missing or nearly empty, and end with the number of sheets and pieces and the size. Both sets are repeated under NOTES in the README.txt in the ZIP.

Questions