Vector shapes
How a vector path is built in Celas Studio: anchors and handles, the three node types, open and closed paths, compound paths, corner radius and path direction.
A Shape layer holds one bezier path, optionally with extra contours, plus a fill and a stroke. You get one by drawing: the Pen, Pencil and the five shape tools all create Shape layers, which is why Shape is not in the Add Layer menu. A new layer is named after what made it: the Pen and the Pencil give you Shape 1, Shape 2 and so on, while the shape tools name theirs Rectangle 1, Ellipse 1, Polygon 1, Star 1 or Line 1.
Anchors and handles
Every node on a path has a position and two handles, one for the curve arriving at it and one for the curve leaving it. Drag a handle with the Node tool (A) to bend the segment beside it. A handle that is not in use sits exactly on top of its anchor, so a straight corner shows no handle at all until you pull one out.
Alt-drag an anchor to pull a pair of symmetric handles out of it. Hold Alt while dragging a handle to break the tangent and move that handle on its own. Shift-click an anchor adds it to the vertex selection; Shift while dragging constrains the move to one axis. Arrow keys nudge the selection by one document unit, or ten with Shift held.
The three node types
The node type is stored on the node, not guessed from its geometry, and it is shown by the marker drawn on canvas as well as by the Sharp / Smooth / Smart pill in the Node tool options bar.
| Type | Marker | Behaviour |
|---|---|---|
| Smart | Circle | Handles are mirrored: the same length on both sides, always in line |
| Smooth | Diamond | Handles stay in line but their lengths are independent |
| Sharp | Square | Handles are fully independent, so the node can be a corner with two curved sides |
Double-clicking an anchor with the Node tool toggles it between smooth and sharp: going sharp retracts both handles onto the anchor, going smooth rebuilds them. Setting a node to Sharp never deletes its handles: it only frees them from each other.
Open and closed paths
A path is open until its ends meet. With the Pen tool (P) and at least three points down, clicking within a few pixels of the other endpoint closes the path and ends the stroke. Escape or a right-click finishes an open path and keeps it selected, and clicking on the endpoint of an existing open path resumes drawing from that end. Close Path in the curve-op buttons does the same thing from the options bar, and Break Curve opens a closed path at the selected node.
The Properties panel shows the point count and whether the path is Closed or Open in its Path section. Being closed matters beyond the fill: stroke alignment set to Inside or Outside only applies to a closed shape, and a shape used as a mask must be closed with at least three points.
Compound paths and the fill rule
One Shape layer can hold several contours: a main path plus any number of extra ones. Erasing into a shape, or a Pathfinder operation that leaves holes, produces exactly that. The contours belong to one layer and share one fill and one stroke.
When a shape has extra contours, the Fill section grows a Fill overlaps checkbox. It is off by default, which is the even-odd rule: where contours overlap, the overlap is punched out as a hole. Turn it on for the non-zero rule, where overlapping areas stay filled.
Corner radius
Each node carries its own corner radius, 0 by default. With Radius on in the Node tool options bar, a corner node shows a round handle you can drag along the angle bisector to round it off. The radius stays live (the underlying node is still a corner) and neighbouring radii share the length of the edge between them, capped just short of using the whole edge.
Rounding does nothing on a node whose tangents are already continuous (a Smart node, or a Smooth node with both handles pulled out), on the two endpoints of an open contour, or at angles that are nearly straight or nearly folded back. When you want real geometry instead of a live radius, Convert to Curves bakes every radius on the shape into bezier nodes; the button appears only once some node has a radius.
Direction and the start point
Reverse, in the curve-op buttons of the Pen and Node options bars, flips the winding of the path. That changes which side of an overlap is filled under the even-odd rule, and it flips the direction a stroke writes on in when you animate Expose Start and Expose End.
The start point is where a closed contour begins, drawn on canvas as a red ring on node 0 with an arrow toward node 1. Right-click a node with the Node tool and choose Start Vertex to rotate the contour so it starts there. The rest pose and every vertex keyframe rotate with it, and bone bindings and vertex welds are repaired in the same step, so an animated, rigged shape survives the change.
Per-node extras
Two more properties live on individual nodes, both reached from the pill at the left of the Node tool options bar. Hide Edge mode hides the stroke on the segment that follows the node you click, which is how you draw a shape whose outline is only partly inked. Line Width mode gives the node its own stroke width in pixels, overriding the shape width; 0 means it follows the shape.
Nodes also keep a stable identity for as long as the shape exists. That is what lets vertex keyframes, bone bindings and welds survive inserting, deleting and reordering points instead of jumping to the wrong node.
| P | Pen tool |
| A | Node tool |
| N | Pencil tool |
| U | Shape tool |
| ShiftU | Cycle the shape tools |