Rulers
All nine rulers — straight, parallel, perpendicular, ellipse, concentric, radial, curve and the two surface axes — and the difference between a ruler anchored to itself and one anchored to your stroke.
Reference
- Tool
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- Ruler
A ruler is geometry the pen is pulled onto while you draw. Switch Snap to ruler on, pick a kind, and every stroke is drawn against it.
Nine rulers ship, in two groups in the Ruler picker: seven Flat rulers, and two under Follows the surface that are only meaningful on a bent layer.
Options
Switches the guide on. On its first use in a shot the ruler is centred in the view.
The nine kinds, below.
The ruler's heading. Shown only for the kinds that have one — Concentric, Curve, Surface U and Surface V do not, because their geometry is not a heading. Dragging the blue grip on the canvas moves this slider.
How hard the ruler pulls. At 100 the stroke lands exactly on the ruler, which is what every other drawing application does. Below that the pen is only pulled part of the way, so your own wobble still shows through — useful for keeping a ruled drawing from looking traced. At 0 the ruler does nothing.
Draws the ruler on the canvas.
Curve ruler only. With this on, your next stroke is captured as the rail instead of being drawn as ink.
The ruler is moved by its handles, not by numbers: an amber dot at the origin slides it, a blue grip turns it, and an ellipse ruler adds a third grip for its size.
Two kinds of ruler
The distinction that matters most is not what shape a ruler is, but what it is anchored to.
Anchored to itself. Straight, Ellipse, Curve, Surface U and Surface V sit where you put them. Every stroke is pulled onto the same geometry, so ten strokes drawn against a straight ruler all land on one line.
Anchored to your stroke. Parallel, Perpendicular, Concentric and Radial take their position from wherever the stroke began and use the ruler only for direction or centre. Ten strokes drawn against a parallel ruler come out as ten separate parallel lines — one through each starting point — which is how you hatch without re-placing the ruler between strokes.
The first point of a stroke is never snapped
For the stroke-anchored rulers, the first sample has to stay where the pen actually landed, because that point is the anchor. Snapping it first would drag every stroke back to the ruler's own origin and collapse a set of parallels onto a single line.
The nine rulers
Flat
Straight
One infinite line. Every stroke is pulled onto it.
Parallel
A fixed heading, but the line runs through wherever this stroke began. Each stroke is parallel to the last without the ruler having to be moved.
Perpendicular
Parallel, turned 90°. The pair is how you hatch and then cross-hatch: draw a set against Parallel, switch to Perpendicular, draw the crossing set at the same Angle.
Ellipse
Snaps onto an ellipse — a circle when the two radii match. The ellipse's size is set by its own grip on the canvas and its tilt by Angle.
Concentric
Rings sharing one centre. The radius is whatever the stroke started at, so each stroke becomes its own ring: start close to the centre for a tight ring, further out for a wide one.
Radial
Spokes radiating from one centre — the dual of Concentric. You pick the spoke by where you start the stroke, and the stroke then runs straight out along it.
Curve
A rail you drew once, snapped to on every stroke afterwards — a French curve. Switch Draw the rail next on, draw the shape you want, and that stroke becomes the rail rather than ink. Every stroke after it is pulled onto that shape.
Follows the surface
These two exist because canvas space maps onto whatever shape the layer's drawing surface has.
Surface U
The straight ruler pre-aimed along the surface's own s axis. On a flat layer that is just a straight line. On a cylinder it is a ring around the tube; on a sphere, a great circle.
Surface V
The same, along the t axis — the other way round the form.
There is no separate 3D ruler machinery: a ruler is drawn through the surface's own mapping, so it is already a curve on the solid, and it stays glued there when the camera orbits.