Draw is a pencil. Press, draw around a shape in one stroke, and let go: the line is closed, cleared of the small accidents a hand leaves, and fitted with smooth curves that keep the corners you meant.
What it does
Press N (or B, or D), or choose ‘Draw’ on the rail. Every stroke becomes a closed shape. As you come back toward where you began, a small ring appears on the starting point: let go while it shows and the shape closes there. The closing distance is 24 screen pixels, and the ring waits until the stroke is at least three times that long, so it does not light up the moment the pencil goes down. Let go anywhere else and the gap is closed with a straight line. A stroke that encloses nothing makes nothing: a straight line, or a line drawn out and back along itself, has no inside to cut. It has to be less than half a screen pixel wide on average; come back two pixels away and it is a thin shape, which asks for its flip as usual.
When you let go, the stroke is tidied in stages:
- Trim. A hand closing a shape runs on past where it began. If the stroke came back to its start and then left again, the part after the closest approach is cut off. Nothing else is trimmed: a stroke that crosses itself elsewhere is kept as drawn.
- Clean. The line is resampled at an even spacing of one screen pixel, because a browser records the pointer by time, not by distance, and every later step measures along the line. The little hooks at pen-down and pen-up are dropped.
- Find the corners. At every point the tool measures how sharply the line turns, over a short span and over a longer one. A wobble turns over the short span only, a broad bend over the long one only; a corner turns over both. Where the pen slowed down, a slightly gentler turn still counts, because a hand slows into a corner and sweeps around a curve.
- Fit. The line is cut at the corners, and each piece is steadied and then fitted with as few curves as will stay close to it. A piece that stays close enough to straight becomes a true straight line. Where two straight sides meet, their corner moves to where the two lines cross.
- Join. If you began halfway along a straight side, the two halves of that side become one, so a hand-drawn square has four anchors wherever you started it.
How hard all this works is set by ‘Drawing’ on the ‘Controls’ tab: five stops from ‘Accurate’ to ‘Smooth’, starting in the middle. One slider moves several things together: how closely the curves must follow your line, how sharp a turn must be to count as a corner (32° at ‘Accurate’, 45° in the middle, 65° at ‘Smooth’), how straight is straight enough, and how much a shaky line is steadied. All of it is measured on the screen, not on the paper, so the same marks give the same result at any zoom, and zooming in lets you draw finer detail. See Drawing.
While the stroke is under way, hold Option (Alt) and the line grows by one straight segment from the last point, stretching to the pointer like a rubber band; add Shift and it keeps to 45° steps. Let go of Option and you are drawing freehand again from its end. Before a stroke begins, the same keys lend you other tools while held: Command for Move, Option for Points, Shift for Curves. On a touch screen, a second finger means a pinch, not a drawing, and abandons the stroke.
The finished stroke is an ordinary path of anchors and handles, and Points and Curves can change any of it.
Why it works this way
A hand is expressive and noisy at once, and the whole job is telling the two apart. The first version of this pencil smoothed the whole stroke in one pass. That kind of smoothing cannot tell a corner from a bend, so it rounded every corner it met, and a hand-drawn square came out a lozenge. Finding the corners first, then fitting only between them, keeps what was meant and loses what was not.
Measuring the turn over two spans is what separates tremor from intention. The pen’s speed is a second opinion and only ever a tie-breaker: it can tip a borderline turn into a corner, never invent one.
Every stroke closes because a notan is made of regions, not lines. A cut has to have an inside.
The metaphor
The pencil is the most forgiving drawing tool there is: light, erasable, the instrument of first thoughts. Draw keeps what a pencil is good at, speed and the feel of the hand, and adds something no pencil does. It redraws your line as you lift it, the way an inker in a drawing office or a comics studio once went over a pencil sketch with a steady pen, keeping the intention and dropping the hesitation.
Where the metaphor breaks: a pencil line is only ever a line, and this one is always a boundary, closed around an inside. The moment you let go it stops being a trace of your hand and becomes a path of points that can be edited. It also forgets how hard you pressed. Pressure is recorded, but nothing uses it yet.
A history
In art
Giorgio Vasari, writing his lives of the artists in the sixteenth century, called drawing, disegno, the father of the three arts of architecture, sculpture and painting. A drawing was where an idea first became visible, and its changes of mind, the pentimenti, were part of its interest. Gesture drawing, taught by Kimon Nicolaïdes among many others, trains the hand to catch the movement of a thing before its details, which is exactly the kind of line this tool expects.
The link to paper-cutting is closer than it looks. Matisse described his late cut-outs as drawing with scissors: cutting straight into color instead of drawing an outline and filling it in. Draw is that in reverse, a drawn line that becomes a cut.
In printing
For most of printing’s history a drawing had to be translated before it could be printed. A craftsman cut it into wood or engraved it into metal, and the line on the page was his as much as the artist’s. Lithography changed that. Around 1796 Alois Senefelder, in Bavaria, found that marks made with a greasy crayon on fine limestone could be inked and printed: the damp stone refused the ink and the grease held it. Artists could draw straight onto the printing surface and the printed line was the hand’s own. Nineteenth-century artists such as Honoré Daumier and Henri de Toulouse-Lautrec made great use of it.
The pencil has a history of its own. A deposit of unusually pure graphite found at Borrowdale in Cumbria in the sixteenth century could be cut into sticks and used as it came, and it supplied pencil makers for generations. In 1795, with France cut off from English graphite by war, Nicolas-Jacques Conté mixed powdered graphite with clay and fired it; changing the proportions changed the hardness, and pencils are still made that way. There has never been any lead in them.
In technology
Computers began tidying hand-drawn lines almost as soon as they could read them. The RAND Tablet of 1964, one of the first graphics tablets, was used with a program called GRAIL that recognized hand-drawn letters, symbols and shapes and redrew them cleanly on the screen. In the early 1970s Urs Ramer, and separately the cartographers David Douglas and Thomas Peucker, published ways of throwing away most of the points of a digitized line while keeping its shape; Douglas and Peucker wanted it for the outlines on maps. In 1990 Philip J. Schneider published, in Graphics Gems, a method for fitting smooth Bézier curves to a digitized line, splitting it wherever the fit is worst and trying again. The smoothing this app applies to each piece is built on it.
Finding the corners first is younger research. ShortStraw, published in 2008 by Wolin, Eoff and Hammond, resamples a stroke evenly and then measures, at each point, the straight distance across a few samples either side; at a corner that distance shrinks. This app’s corner finder works in the same spirit. And the ‘Accurate’ to ‘Smooth’ slider is borrowed from Illustrator’s Pencil, whose Fidelity setting has the same five steps between the same two words.
In professional software
Freehand tools go by pencil, brush or freeform pen, and the setting that matters is how much each one tidies your hand, which programs call fidelity, smoothing or streamline. Some go a step further and recognize a rough shape as a clean rectangle, ellipse or polygon.
- Adobe Illustrator. The Pencil (
N) is the model for this tool: double-click it for its options, where the ‘Fidelity’ slider runs from ‘Accurate’ to ‘Smooth’. The Smooth tool tidies part of an existing path as you drag along it, and ‘Object › Path › Simplify’ thins out the anchors of any path. The Shaper tool (Shift-N) turns a rough rectangle, ellipse or polygon into a crisp, editable shape. - Adobe Photoshop. Brushes paint pixels, and the ‘Smoothing’ value in the options bar steadies a stroke by letting it trail behind the pointer. To draw a path freehand, use the Freeform Pen tool, whose ‘Curve Fit’ setting, in pixels, trades detail for fewer anchors.
- Procreate. ‘StreamLine’, set for each brush in the Brush Studio, smooths a stroke as you draw it. QuickShape does for simple figures what Draw’s corner finder does: end a stroke by holding your finger or pencil still, and it snaps into a clean line, arc, ellipse, triangle or quadrilateral.
- Inkscape. The Pencil tool (
P) has a ‘Smoothing’ value in its toolbar that does the work of the ‘Drawing’ slider here. - Autodesk AutoCAD. The
SKETCHcommand records a freehand line as lines, a polyline or a spline. Its Increment sets the length of each recorded segment, and for a spline its Tolerance sets how closely the curve must follow your hand.
What carries over. Every freehand tool trades accuracy against smoothness, and the setting is worth checking before you blame your hand. The difference to watch is closing. Draw closes every stroke, while Illustrator’s Pencil and Photoshop’s Freeform Pen leave a stroke open unless it ends where it began, so close a shape yourself before it goes to a cutter.
Try this
- Draw a square quickly in one stroke, starting halfway along a side. Take Points and count the anchors.
- Set ‘Drawing’ to ‘Accurate’ and draw a wobbly leaf; set it to ‘Smooth’ and draw the leaf again. Compare the anchors.
- Draw a wave freehand along the top, then hold Option for three straight sides back to the start.