Masks and Groups
Groups, sub-layers and masks — what each composites, their controls, and how a mask relates to the layer that owns it.
Reference
- Panel
- Layers
Four structures organise a layer stack beyond a flat list: groups, which composite several layers as one unit; sub-layers, which stack on a single layer's own plane; the mask, which you paint to shape a layer's visibility; and the mask link, which uses other layers as a stencil. All four are created from the Layers panel's + menu.
Groups
A group is a folder. It composites its member layers together as one unit, applies its own effect stack to that result, and then composites the result into the scene with the group's opacity and blend mode. A group is therefore the way to treat several layers as a single object — to fade them together, to blend them together, or to grade them together.
Membership is recorded on the layers themselves. A group does not hold a list of its members, which is why removing a layer from a group never disturbs the others.
Creating and dissolving a group
New group with this layer wraps the active layer in a new folder and selects it. Folders are
named Group 1, Group 2, and so on. A group always starts with exactly one member — the layer
that was active when it was created.
To add further layers, use Move to group from the + menu or from a layer row's long-press context menu, and pick the group by name. Remove from group takes a layer back out. Both items appear only when they apply: Move to group when the layer is not already in a group and at least one group exists, Remove from group when it is in one.
Ungroup dissolves the folder and clears the membership of every layer in it. The layers themselves are not deleted; they return to the stack as loose layers. This is the only way to remove a folder — when a group is the active target, the action row's bin deletes the active layer instead. A folder is emptied by Ungroup, not by the bin.
Group controls
Scales the group's composited result as it composites into the scene. This is a true group fade: the members composite among themselves at full strength first, so overlapping members do not show through one another as they would if each were faded individually.
How the group's composited result combines with the scene below it. The same thirteen modes as a layer; see the Layers panel.
Dissolves the folder, leaving every member in the stack.
On the group header row. Hides the entire folder and everything in it.
Shows or hides the group's members in the panel. This affects the panel only and never the render.
A group has no mask link of its own. To stencil a group, apply the mask link to its members.
How a group composites
A group composites as a single unit at the depth of its frontmost member. Its members are composited back-to-front within the group, then the group's effects, opacity and blend mode apply to the finished result before it composites into the scene.
Two consequences follow. A group with no members is skipped entirely — an empty folder renders nothing and occupies no depth. And because the group takes the depth of its frontmost member, a group's position in the scene follows the member nearest the camera, not the group's position in the panel.
Sub-layers
A sub-layer is a 2D stack that lives on a parent layer's own plane. The sub-layers composite together with the parent's strokes first, and only then does the finished layer composite into the 3D scene. A sub-layer is the right structure for artwork that belongs to the same plane as the layer it accompanies — shading, line work and colour that must travel with the layer as one piece.
Paint sub-layer adds one to the top of the active layer's stack, names it Paint 1, Paint 2,
and so on, and makes it the draw target immediately.
A sub-layer carries its own opacity, blend mode, visibility, effect stack and mask link. Its effects apply to the sub-layer's content before it composites into the parent layer. A sub-layer cannot carry a mask of its own; the mask belongs to the main layer.
In the panel, sub-layers are listed with the top of the stack first.
The layer mask
A mask shapes a layer's visibility, not its pixels. You paint into it, on the layer's own plane,
and the strokes underneath are never touched — erase the mask and the artwork returns intact. The
panel states the principle directly: Painting shapes visibility (not pixels).
Each main layer may have one mask. Sub-layers cannot have one.
Creating and painting a mask
Mask on the + menu adds a mask to the active layer and activates it, so the next stroke paints into the mask rather than onto the layer. The item appears only when the layer has no mask yet.
While a mask is active it takes precedence over any active sub-layer as the draw target. Select the layer row again to return to painting the artwork.
What painting does
The direction is set by a single toggle, and it is worth reading carefully.
Reverses what painting into the mask does.
Off — the layer starts fully visible and painting hides. Paint into the mask to take parts of the layer away.
On — the layer starts fully hidden and painting reveals. Paint into the mask to bring parts of the layer back.
The eye on the mask row switches the mask off without deleting it, restoring the layer to full
visibility. A disabled mask's row reads off.
The panel's help text tracks the toggle, reading Paint to hide or Paint to reveal to match.
How a mask relates to its layer
The mask applies after the layer's sub-layer stack has composited, modulating the alpha of the whole finished layer. It therefore shapes the parent's strokes and every sub-layer together, as one. A mask cannot be used to hide one sub-layer but not another.
A mask has no opacity, no blend mode and no effect stack — the Effects button is disabled while a mask is the target. It is also the one target that cannot be reordered: Move up and Move down are disabled for it. Its position is fixed directly beneath its layer's row and above that layer's sub-layers.
The action row's bin deletes it, with the hint Delete mask.
Masked by: using other layers as a stencil
A mask link makes other layers act as a stencil for this one. It is available on main layers and on paint sub-layers. Groups do not have one.
Chooses which layers or sub-layers stencil this one. The menu lists every eligible layer other
than the target, each toggling on and off; when there are none it reads No other layers. The
menu's label summarises the choice: None, the source's name when there is exactly one, or
2 layers, 3 layers, and so on.
Reverses the stencil. Off — the target shows only where a source is painted. On — the target is hidden where a source is painted. Appears once at least one source is chosen.
Two behaviours are worth stating plainly.
Multiple sources combine as a union. The target is masked wherever any chosen source has paint, not only where they overlap.
A source stencils even while it is hidden. Turning a source layer's eye off does not stop it masking. A layer can therefore be used purely as a stencil, invisible in the render but shaping another layer.
A layer that has a mask link shows a dashed-circle dot in its row.
Deleting a layer or sub-layer that is being used as a stencil is safe. Its reference is stripped from every mask link that named it, and a link left with no sources is dropped entirely — a deleted stencil never lingers as a dangling reference and never hides its target.
How boundary-scoped operations read the stack
Some operations read more of the stack than the target they act on. The Fill tool is the clearest case: its boundaries can come from more layers than the one the fill lands on.
Which layers' ink closes the region being filled. The fill itself always lands on the active target, whichever option is chosen.
This layer — only the active layer or sub-layer.
Layer + sublayers — the active main layer, every one of its sub-layers, and its mask.
All layers — every visible layer, with their sub-layers and masks.
The default, Layer + sublayers, reads a main layer together with its sub-layers and its mask —
it does not read a folder, despite what the grouping of the words suggests. This is what allows an
outline drawn on the main layer to close a fill made from one of its paint sub-layers: the fill
lands on the sub-layer, but the outline on the parent still forms the wall. Strokes painted into the
layer's mask act as boundaries on the same terms.