Boolean & liquid shapes

Two ways to combine vector shapes: the destructive Pathfinder buttons on the toolbar, and the live boolean group. Both are also in the Vector menu.

Celas Studio has two boolean systems and they are deliberately different. The Pathfinder buttons on the toolbar consume the shapes you selected and hand back one new shape. The boolean group wraps the same shapes in a group and computes the result while you keep editing the parts. Both need at least two selected layers: Pathfinder works on Shape layers only, while the boolean group also takes paint layers, images and symbols.

Pathfinder: one new shape#

The Pathfinder group sits on the toolbar as five buttons: Add (Union), Subtract, Intersect, Xor and Divide. When the window is narrow the group collapses to the button you used last and fans out when you hover it. The same five are in Vector ▸ Geometry, greyed out exactly when their buttons are.

• Add (Union) fuses the selection into one outline.
• Subtract cuts the shapes above out of the bottom one.
• Intersect keeps only what all of them cover.
• Xor keeps everything except the overlap, so the overlap becomes a hole.
• Divide cuts the selection along every edge and keeps each resulting piece.

The operands are removed and replaced with the result, which is a single Shape layer: a compound one when the outcome has holes or separate islands. It is a normal editable path, so you can carry on with the Node tool afterwards. Rounded, straight, concave and cutout corners are turned into real curves before the cut, so a rounded shape keeps its rounded outline in the result.

Divide works on up to eight shapes at a time. With more selected, it divides the first eight, leaves the rest untouched and says so.

Divide and Separate#

Divide and Xor have a second job. Run either on a single compound shape and Celas Studio releases every contour into its own Shape layer, each named Path. That is the way to break an erased or imported outline back into separate pieces. The released pieces start clean: their animation is not carried over.

The boolean group: still live#

Select two or more layers and choose Vector ▸ Boolean ▸ Union (Liquid Shape), Subtract, Intersect or XOR. The same four sit on the Move tool options bar, and are greyed out until there is something to do with them. Celas Studio inserts a group at the position of the front-most selected layer and moves the layers into it. The bottom layer becomes the base, and every layer above it takes the operation you chose.

Nothing is destroyed. Open the group and every original shape is still there, still animatable. Move one and the result follows.

The outline of the combined shape uses the stroke of the bottom Shape piece, including its Dash, Expose Start, Expose End and brush tip.

Each piece has its own operation#

The operation belongs to each piece, not to the group. Select a piece and the four buttons, and the Boolean / Liquid Shape section in Properties, set what that piece does to everything below it. One group can therefore union two pieces and subtract a third, with no nested group for each change of operation. The base piece at the bottom has nothing to act on, so its operation is greyed out.

The group itself carries only an on and off switch. Select the group and the bar shows a single Boolean switch: off, the pieces draw as an ordinary group of separate shapes; on, they fold into one outline again. Projects made when the group had an operation of its own are converted when they open and look exactly as before.

Shape layers are not the only thing that can take part. Raster Cells, images, nested groups and symbols can be pieces too: each keeps its own artwork, and the group cuts it to the combined outline.

Liquid shapes#

A boolean group also has a Blend Radius, from 0 to 1000 px. At 0 the join is a hard one: outlines simply meet. Above 0 the pieces reach for each other and melt together with a smooth neck, the way two drops of water join. Subtract, Intersect and XOR blend at the seam the same way Union does. When two pieces drift too far apart to be linked, the blend simply ends: no thin spike is left reaching from one to the other.

Strokes#

A boolean shape takes strokes into account, with or without a Blend Radius. Every shape's stroke becomes part of the shape at its own width, thick and thin parts included, so a per-vertex Line Width counts too. An open path counts as its stroke alone.

The result is one shape. It is painted with the bottom shape's fill, or with that shape's stroke colour when it has no fill. The bottom shape's stroke, whether plain, brush or dashed, is drawn around the whole outline.

Blend Radius is keyframeable, so a splash can pull apart over time; the other three are settings rather than animated values. The group's three controls are reachable from any selected piece as well as from the group, so you can adjust the seam while looking at the piece, without re-selecting anything. Elasticity and Blend Colors grey out while the Blend Radius is 0, because there is no blend for them to shape.

Three or more pieces combine in one step, so a join depends only on the pieces that actually meet, not on where each one sits in the layer order. The blended outline is fitted with real curves and stays steady while the pieces move or while you pan and zoom. During playback it is computed on the graphics card, and on hardware that cannot do that the app falls back to the processor automatically.

Which one to use#

Reach for Pathfinder when the combination is a decision you have made (a silhouette you will now edit as one path) and when you need Divide, which the group has no equivalent for. Reach for the boolean group when the parts must stay editable or animated, when you want to try operations out, when paint layers or symbols need to take part, or when you want the liquid blend.

Two practical limits are worth knowing. Corner radius does not apply to the extra contours of a compound shape, so radii on a Pathfinder result with holes will not show. And boolean operations have no keyboard shortcuts in Early Access. They are toolbar and menu only.