Triangle draws an equilateral triangle, all three sides equal, standing point up on a flat base. You draw it from its center outwards, and the length of the drag sets its size.
What it does
Choose ‘Triangle’ on the rail (on a phone, under ‘Shapes’). It has no keyboard shortcut.
Press where the center of the triangle should be and drag outwards. The distance from your press to the pointer becomes the distance from the center to each corner, so the triangle comes out one and a half times as tall as the drag is long. The direction you drag in makes no difference: the triangle always stands point up. To turn it, use Move afterwards. A turn of 60°, four Shift-steps of 15°, stands it on its point. A click with no drag makes nothing, as with Rectangle.
Once the drag has begun:
- Shift takes the size from the longer of the horizontal and vertical distances you have dragged, rather than from the diagonal. Dragged at an angle, the triangle would otherwise swell by up to 41%. The tooltip calls this ‘⇧ pins the size’, and the hint line ‘Pin the size’.
- Option (Alt) does nothing here: the triangle already grows from its center, which is why the hint line does not offer it.
- Space moves the triangle without changing its size.
Held before the press, Shift, Option and Command lend you Curves, Points and Move, as with every drawing tool.
The finished triangle is three corner anchors joined by straight lines. Points will add anchors to it but never take a path below three, so a triangle can gain corners and never lose one.
Why it works this way
A regular shape has no corner to start from, only a center and a reach, so it is drawn the way a compass draws: set the point, open the arms. That is why Option, which elsewhere means from the center, has nothing left to add.
Keeping the triangle upright while you drag makes it predictable. If the direction of the drag turned it, every change of size would also be a small, unwanted rotation. Turning is a separate decision, and Move makes it in 15° steps that land on every angle a triangle cares about.
The metaphor
In an American drawing office the set square is simply called a triangle. Two did most of the work: one with angles of 45°, 45° and 90°, and one with 30°, 60° and 90°. The second is exactly half of the shape this tool draws. Cut an equilateral triangle down its height and each half is a 30–60–90 set square.
The deeper ancestor is the compass. The very first proposition of Euclid’s Elements constructs an equilateral triangle on a given straight line: draw a circle around each end of the line, reaching to the other end, and the point where the two circles cross is the third corner. It is the first thing that book teaches, and it needs no measuring at all.
Where the metaphor breaks: a set square is a guide for drawing lines, not a shape to be cut out, and Euclid’s triangle stands on whatever line you give it. This one always stands on a level base until you turn it.
A history
In art
Painters of the High Renaissance, Leonardo and Raphael among them, often gathered their figures into a pyramid, with a head at the apex and a broad base below, which gives a group calm and stability. A triangle balanced on its point does the opposite and looks ready to fall. In a notan the same shape can feel settled or restless depending only on which way up it is.
At the Bauhaus in the early 1920s Wassily Kandinsky held that the elementary shapes had natural colors, the triangle yellow, the square red and the circle blue, and a questionnaire circulated there asked others to make the same match. His book Point and Line to Plane, published in 1926, is a whole grammar of such elementary forms.
In printing
The triangle’s link to printing is thin, and it is better to say so. Its place was on the drawing table beside the press rather than in it. Layout and paste-up artists ruled their verticals by sliding a set square along a T-square, and read scaled drawings off the architect’s scale rule, triangular in section so that its six edges can carry several scales at once. When a page was prepared for the printer, the set square kept its columns true.
In technology
A triangle is the only polygon that cannot change its shape without changing the length of a side. Pin four bars into a square and it folds flat into a diamond; pin three into a triangle and it holds. That is why bridges, cranes and roof trusses are made of triangles.
It is also the atom of computer graphics. Three points always lie in one flat plane, and any polygon can be cut into triangles, so graphics hardware draws nearly everything in three dimensions, faces, landscapes, the worlds of films and games, as meshes of small triangles. Surveyors used the principle long before: measure one baseline with great care, sight the angles to distant points, and a chain of triangles carries exact positions across a whole country.
In professional software
Most programs draw a triangle with a polygon tool set to three sides, dragged out from the center as it is here. The idea that transfers is the compass: a center, a reach and a count of sides.
- Adobe Illustrator. The Polygon tool, grouped with the Rectangle tool, starts as a hexagon. Drag out from the center and press the Down Arrow key until three sides remain, or click once to type a radius and a number of sides. Without Shift the shape turns with your drag; hold Shift to keep a side level.
- Adobe Photoshop. The Triangle tool, among the shape tools (
U), is drawn by its box rather than from its center: Shift-drag for an equilateral triangle, or click once to type a size and a corner radius. The Polygon tool beside it takes a number of sides. - Autodesk AutoCAD.
POLYGONasks for the number of sides, from 3 to 1024, then a center, then whether the radius reaches the corners (‘Inscribed in circle’) or the middles of the sides (‘Circumscribed about circle’). Its Edge option builds the shape on a side you draw instead. - Autodesk Fusion (formerly Fusion 360). The polygon comes as three tools: Inscribed Polygon, measured from the center to a corner; Circumscribed Polygon, to the middle of a side; and Edge Polygon, built on one side. Press Tab to reach the number of sides and type 3.
- Inkscape. The Star/Polygon tool (
*) switches between stars and polygons in its toolbar and takes a number of corners.
What carries over. The drag in Studio Notan runs from the center to a corner, which is what the CAD programs call inscribed. When a plan gives a polygon’s size, check whether it means the distance to a corner or to the middle of a side: for a triangle, the first is exactly twice the second.
Try this
- Drag a triangle at a slant, then drag another the same way, pressing Shift once the drag has begun, and compare their sizes.
- Turn a triangle with Move, Shift held, by four steps of 15°: it stands on its point.
- Take Points and click the middle of each side to add an anchor, then drag the three new anchors toward the center: a three-pointed star.