Layers and scenes

What a layer is here

A layer is a sprite with a position on the canvas. It has its own artwork, its own hint layers, its own solver settings and its own solve, and the results are stacked into one normal map at the canvas's size.

That is a narrower idea than a layer in a paint program, where layers are strokes on a shared surface. These are separate objects photographed together. A crate is solved as a crate whether or not a character is standing in front of it, which is why moving the character changes nothing about the crate.

Every document has at least one layer. Open a single sprite and you have a one-layer scene, which behaves exactly as it always did — the Layers tab shows one row and nothing else about the editor changes.

Adding layers

File ▸ Import ▸ Sprites as layers…, or Add layers in the Layers tab. Pick one file or twenty; each becomes a layer, named after its file, stacked above what is already there.

A Photoshop or Aseprite file can do the same from one document: in the import dialog, Artwork (base) and Artwork (new layer) send each layer into the scene instead of flattening everything onto one sprite. See Importing.

This works from a new document too: the first file becomes the scene, and the rest stack on it. You do not have to import a base sprite first.

New layers arrive at the canvas origin, on top. Drag them where they belong with the Move tool.

Dropping files on the window still imports them as animation frames, not as layers, because a set of PNGs cannot say which it is. See what is shared and what is not for how the two combine.

The Move tool M

Drag a layer to position it. Click picks whichever layer has a pixel under the pointer, topmost first, so clicking through a hole in a sprite selects what is visible behind it rather than what the bounding box says.

The arrow keys nudge the selected layer a pixel, with Shift for ten. They do this only while the Move tool is selected, so that arrows go on meaning whatever has focus everywhere else.

Positions are whole pixels. A layer at a half-pixel offset would need its artwork resampled to composite, which would soften pixel art for no gain — and the arrangement of sprites is a decision made in pixels anyway.

The Layers tab

In the inspector, beside Solver and Lights. Topmost layer at the top, as in every other program with a layer list.

Below the list, the Canvas panel shows the size everything is exported at, and Fit canvas to layers resizes it to contain them all.

Fitting is a command rather than something that happens by itself, because a canvas that resized as you dragged would move every other layer while you were positioning one. A layer is allowed to hang off the edge in the meantime; it is clipped, not rejected.

Settings are per layer

This is the opposite of how frames work, and the reason is the same in both cases.

Frames share settings because a per-frame setting is how two frames of one animation come to disagree. Layers are different objects, and a setting that suited a stone wall has no business governing the glass bottle in front of it. So each layer keeps its own — select a layer and the Solver tab shows that layer's settings, changed for that layer alone.

Consequently each layer is solved separately. Selecting one solves it if it has not been solved yet; the others are solved quietly in the background so that the composited picture is complete without waiting for a click on each.

How the normals are stacked

Where two layers overlap, the nearer one wins outright. Its normals replace what is behind, rather than blending with it.

Blending would be the wrong answer, and not by a little. A normal map does not average like colour: halfway between two surfaces facing apart is a third surface facing somewhere neither of them does, which lights like a crease that no object has. Two sprites overlapping have no shared surface to interpolate — one is simply in front.

The exception is the anti-aliased fringe of a sprite, where a pixel is genuinely part-covered. There the two are mixed in proportion to coverage and the result is scaled back to unit length, so the seam does not develop a dark rim.

Empty canvas exports as flat, facing the camera. So does a layer that has not been solved yet, which is why a scene opened and immediately exported may be missing a layer's detail — the status bar says when solves are outstanding.

Layers and frames together

A scene can be animated, and the two ideas meet under one rule: a layer with fewer drawings than the scene has frames holds its last one.

So a lamp post drawn once stands in every frame of a six-frame walk cycle, without anyone duplicating it six times. A character with six drawings walks. Both are on the same timeline.

The strip along the bottom is the scene's timeline, not the selected layer's drawings. Its thumbnails are the composited scene, its length is the longest layer, and the dot on a frame means the layer you have selected has hints painted at that frame. A per-layer strip would vanish the moment you selected the lamp post, leaving no way to step the animation while working on a prop that appears throughout it.

Painting on a layer that holds one drawing across six frames paints it at all six, and the dots say so. That is the same fact as the rule above, seen from the brush end.

Projects and export

A project saves the whole scene: the canvas, every layer's artwork and hints and settings, each layer's position and whether it is visible, and the frames. See Files and presets.

Exporting gives you one normal map at the canvas size, composited. The derived maps work the same way: a height map of one layer is not a height map of the picture, so they are all taken from the composite. See Exporting.

The layers are not separately exportable. If you want a normal map per sprite, solve them as separate documents — which is what the batch tool does to a folder.

What this does not do yet

• No blend modes, no opacity. A layer is opaque where its artwork is opaque. Both would mean deciding what a half-present surface is, and there is no useful answer.
• No groups, no masks.
• No per-layer export, as above.
• Frames cannot be added, removed or reordered on an open document, for layers any more than for a batch.

When not to use layers

If your sprite is genuinely one object, it is one layer. Splitting a character into head, body and arms as separate layers is not free: each gets solved on its own silhouette, so the neck and the shoulder acquire rims where they meet the body, and you have manufactured three seams to fix.

In front D is the tool for parts of one object that overlap. Layers are for separate objects that happen to share a picture.