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Free points, sliders on objects, intersections, midpoints, dividing spans, and nudging with the arrow keys.
Points are the anchors everything else is built on. Locus keeps several kinds of point, and the difference between them is how each one is positioned - some you drag freely, some are pinned to a curve, some are computed from other objects and update on their own.
The way a point is drawn tells you whether you can move it.
- A solid disc is a free point. You put it there and you can drag it anywhere.
- A ring with a dot in the middle is a point that is tied to something but still yours to move along it: a point on an object, or one of a circle's divisions. Drag it and it slides where it is allowed to go.
- A hollow ring, with nothing in the middle, is a calculated point. Crossings, midpoints, the divisions along a segment or an arc, and tangent points are all calculated: the construction decides where they are, so there is nothing to drag. Move what they are built from and they follow.
So the rule reads off the glyph: filled means free, ringed means it moves on a leash, hollow means the geometry decides.
A free point is one you place anywhere and drag at will. It's the most basic building block and behaves like a parameter of your design: move it, and everything built on it follows.
Expand a free point's row in the Layers panel and you'll find editable X and Y fields. Type a number to set a coordinate exactly. These fields also accept simple + and - expressions, so you can type something like 12 + 5 to add, or lead with a minus to subtract - handy for nudging a coordinate by a known amount without doing the arithmetic yourself. Edits commit on Enter and are a single undo step.
Tip
To place a point at exact coordinates in one move - rather than dropping one and then editing it - type the coordinates straight into the command palette. See Typing coordinates.
Note
Only hand-made free points are editable this way. Points that a node created, or that are derived (sliders, intersections, midpoints), show their coordinates read-only - they're driven by their parents, so you change them by changing what defines them.
When two or more real, pickable points land on the same spot - a hand-placed point sitting exactly on a realized node point, say - clicking there with the Point tool doesn't silently grab whichever one happens to be on top. A small chooser pops up listing every candidate so you pick the one you actually mean, the same disambiguation chooser used elsewhere for an overlapping selection (see Getting around the canvas). A single point, a bare crossing, or empty space is unaffected - the chooser only appears once there's a real stack to choose from.
Drop a point onto a segment, ray, line, circle, arc, or ellipse and it binds to that curve, free to slide along it but never off it. These are often called gliders. When you drag one, it stays projected onto its host; on an arc or elliptical arc it clamps to the sweep, and on a full circle or ellipse it wraps around.
You can create one deliberately with the on-object tool, or just drop a point on a curve while drawing - the green-ring snap cue (see the canvas guide) tells you the bind will happen.
Click where two objects cross and Locus makes an intersection point bound to both of them. It re-computes every frame, so it rides the crossing as either object moves - drag a circle's radius and the intersection tracks along. This works across every combination of segments, lines, rays, circles, and arcs.
An intersection point remembers its two source objects, and you can swap either one from the Layers panel: the point re-seats itself onto the nearest crossing of the new pair.
The midpoint tool drops a point exactly halfway between two points, tracking both as they move. There's also a single-segment form: click one segment and you get its midpoint directly, without picking the two endpoints separately.
The midpoint is a dual-form construction - it can be defined either by two loose points or by a segment, and you can redefine it between the two later. Double-click its reference row and pick a segment to switch it to segment-defined, or pick points to switch it back. (The perpendicular bisector works the same way - see Lines, rays & segments.)
Divide is the midpoint's bigger sibling. Pick two points - or a single segment - then enter a part count, and Locus drops the interior points that split the span into that many equal pieces. Ask for four parts and you get the three points between the ends. With a count of two, Divide gives you exactly the single midpoint, so it's a clean generalization of the same idea.
With the modeling pane focused (and not typing in a field), the arrow keys nudge the selected point by a small step. Up moves it up, and the four keys map to the obvious directions. Hold Shift to move ten times as far for a coarse jump, or Option for a tenth of the step for fine adjustment. Nudging several selected points at once is a single undo step.
The step size is set in Settings and is expressed in your current working unit, so the default is a tenth of a millimeter and scales sensibly if you switch units.
Gliders nudge too, but they move along their host rather than in free X/Y. The arrow you press drives the point in whichever direction runs along the curve - so on a shallow curve the left/right keys move it and on a steep one up/down do. A key pressed straight across the curve still moves the point rather than doing nothing. When a glider is nudged into the clamped end of its host, the keypress simply does nothing (no wasted undo step).
Note
Arrow nudging applies to free points and gliders. Computed points - intersections, midpoints, divide points - and locked points aren't nudged, because their position comes from their parents.
Turn on Auto-hide points in Preferences and the scaffolding points a construction leaves behind tidy themselves away the moment it finishes - hidden in place, not deleted, and always reachable again from their own eye toggle in the Layers panel.
That includes a Midpoint or Intersection point made on its own, with nothing else built alongside it - they're construction aids in service of the drawing, not the drawing itself, so the preference hides them just like it hides a point left over from drawing a curve. The one point kind auto-hide leaves alone no matter what is a bare free point dropped with the Point tool - since placing a free point is the whole action, there's nothing to tidy away. Divide points and points you already had before the operation are never touched either way.
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- In the node graph: Point - build the same point as a node.