SketchASin the studio

Arc by radius in the tile editor

Arc by radius draws a curved joint inside a pattern's tile from its two ends and a radius, bulging to the side you point. You give the radius by pointing or by typing it, and the arc drawn is the shorter one between the two ends.

What it is

Arc by radius draws an arc between two points you already know, with a radius you choose. After the two ends, the pointer says two things: the side the arc bulges to, and, by its distance from the middle of the line between the ends, the radius. The arc drawn is always the shorter one between the two ends, so at most a half circle. The arc is one joint, and it stays a true arc everywhere.

It is the same Arc by radius as in the other editors of the studio, acting here on the joints of the tile.

When to use it

To join two points with an arc of a known radius.
To curve a side between two corners you already have.
When you know a point the curve passes through instead, Arc is simpler.

The steps

Take the tool. Type A then S one after the other, or click Arc by radius on the bar. It shares its button with Arc and Arc by centre. The A opens Arc for a moment, and the S completes this one.
Pick the start. Click it, or type x;y and press Enter, measured from the tile's lower-left corner.
Pick the end. Click it.
Give the side and the radius. A ghost arc follows the pointer, bulging to its side. Click to draw it. To be exact, keep the pointer on the side you want, type the radius and press Enter. If the ghost is drawn in the refusal colour, the click would be refused.
Draw the next one or finish. The arc stands, selected, and the tool waits for a new start. Escape drops the points you placed, then leaves the tool for Select. Ctrl+Z undoes the last arc. Press Done on the bar at the foot to hand the tile back.

What it refuses

A radius too short. A typed radius shorter than half the distance between the two ends cannot reach them both, and the hint says that point makes no shape. While you point, the radius never goes below that half.
Two ends that are one point. They make no shape, and the hint says so.
An arc that leaves the tile. If any part of the curve would stand outside the tile, nothing is drawn, and the editor says a shape must stay inside the module.

What it writes to the contract

Nothing while you work: the change stays in the tile editor, where Ctrl+Z steps back through it. When you press Done, the whole tile is written to the project's patterns in one step you can undo, every joint as its points in metres from the tile's lower-left corner. An arc is stored as its two ends with the curve between them, so it stays a true arc. A standard pattern is never changed: Done saves the project's own version of it under the same name, and every surface that lays it follows. Save as new writes a new pattern instead. Cancel writes nothing.

Common questions

How do I draw an arc of an exact radius between two points?

Pick the start and the end, point to the side the arc should bulge to, type the radius and press Enter.

Why was my typed radius refused?

A radius shorter than half the distance between the two ends cannot reach both of them, so no arc is drawn. Type a larger radius.

Can this tool draw more than half a circle?

No. It draws the shorter arc between the two ends. For a longer arc, use Arc by centre or Arc.