#Corner fillet and chamfer

#How to do it

• Fillet (key F): click the corner of two lines or of a line and an arc, type the radius into the field at the corner, Enter.
• Fillet by its chord or arc length: on the bar above press Chord (the straight distance between the two ends of the arc) or Arc length instead of Radius, then click the corner, type the value, Enter.
• Chamfer: click the corner of two lines, type the size into the field at the corner, Enter. The size is the length of the cut itself; its dimension stands on the two ends of the cut, and the cut stands back from the corner equally along both lines.
• Chamfer by two values: on the bar above press Two distances (Leg 1 and Leg 2) or Leg and angle (Length and the Angle between that line and the cut); Symmetric gives one size, the length of the cut. The first value runs along the line you click nearer to: click the corner a little to the side of that line. Type the first value, Tab to the second, Enter.
• The corner of the lines: choose the lines (with Shift, if there is more than one) — the corners they make are cut together, by one value and one Enter. With two lines that share a corner already chosen, the button offers to take that corner off straight away.
• Fillet every corner of the contour: select the contour, press the button, type the R of every corner, Enter.
• A corner at a crossing: two lines going through each other make four corners. Click the fillet or the chamfer by the crossing (or choose both lines with Shift) - the preview of the corner follows the pointer from quarter to quarter. Click in the quarter you want: the preview changes colour and stays there, and the field of the size opens beside it. Both lines are cut at the crossing, and the other two halves stay lines. One Ctrl+Z brings the whole lines back; so does Esc before Enter.
• A corner at a point of several shapes: where the corners of several shapes meet at one point, the same - click the point, the preview follows the pointer, click on the side of the corner you want.

#How corners are named

A corner is not something one points at. A corner is what the chosen lines make. The field opens at once for the whole set, and one value cuts all of it on one Enter, as one step of undo.

A corner exists where two chosen lines share a point (coincident ends). A plain crossing of two lines is not a corner.

• a triangle of three lines is three corners; four lines of a polyline are three; two separate pairs are two.
• A line that meets none of the chosen ones adds nothing: it is half of the next corner and waits for company. The corners named before it stay where they are.

The lines at one point are paired two at a time, in the order they were chosen. A line already in a corner at that point makes no second corner there.

• A cross of four lines: choose A — no corners; add B — AB appears; add C — C waits; add D — CD appears.
• Let B go — only CD is left and A waits. No corner AC arises: nobody asked for it.
• Let C go as well — AD is what stands. Corners are remembered, not rebuilt from the selection afresh on every click.

A joint of two segments on one straight line (180°) is not a corner — there is nothing to cut there. If a third chosen line arrives at such a point it is not taken, and the status names that point: the corners at a point are taken two at a time, and the third would have to be cut against a straight joint.

#Shift and the single selection

Shift is the only way to choose more than one line, as in ordinary selection.

• A click without Shift is a single selection: only the line under the cursor is chosen.
• A click without Shift puts the tool in single mode, wherever it lands — on a line, on a point, or on empty space. A click on a point and a click on empty space do not take the chosen lines away: they speak about the mode alone.
• Shift + click on a line adds it to the set (or takes it out again if it is already chosen).
• A click on a point does not move the choice of lines at all, with Shift or without it. A point is not one of the lines a corner is cut from.

#Corners named at a point

A point where nothing stands may name a corner of its own. While the cursor is inside the zone of that point (three times as wide as the point is picked), a yellow preview of the corner a click there would name is drawn; out of the zone it disappears. The click makes it violet — a corner in the set.

• Where more than two lines stand, the yellow preview shows the pair the cursor stands between.
• Where a corner of the lines already stands at that point, no preview is drawn and a second corner cannot be named there: it is one place, read twice.
• A click on a point carrying a corner named at the point takes it away, with Shift or without it; the point is free again.
• A click on a point carrying a corner of the lines puts that corner away (it is not deleted), and the same click brings it back.
• A corner put away goes when one of its lines is let go, hidden or not: it is a corner of those two lines. Choosing the line again makes the corner again, and this time it stands.
• A corner of the lines that takes the place of one named at the point kills it: it is one place, and there is one corner there.
• A corner named at a point also dies when one of its lines is let go: it is a corner of those two lines.

#Lines chosen before the mode

Lines chosen before the tool was taken stay chosen and become that same set: the corners they make are rounded or chamfered exactly as if they had been chosen with Shift already in the mode.

#The value and the undo

One value cuts the whole set. It is held by the tightest corner in the set and by what the lines between the corners spend on themselves: rounding every corner of a rectangle takes half its short side. A chord or an arc length is kept on every corner of the set, each corner making the radius of its own angle. If one corner of the set does not take the value, no corner is cut: the reason is written at the field — type a smaller value.

• Enter (or the tick) applies the whole set — one step of undo.
• Esc cancels.
• The value is remembered for the next corner.

#What you get

A fillet inserts an arc and adds two tangencies and a radius dimension - or, given by its chord or arc length, a dimension of the chord or of the arc length; a chamfer adds a segment and its dimensions, measured from the sharp corner: the legs, or a leg and the angle. The sharp corner stays as a point the dimensions stand on. All of these are constraints: move a side — the corner rebuilds itself; change the dimension — the fillet changes.

Fillets usually go last, once the contour is defined: before that they get in the way of picking corners.

#If it did not work

• The size is not taken — it is more than the corner holds (longer than a side); the reason is written at the field.
• A chord or an arc length is not taken — the arc it makes reaches past the end of a side. Type a smaller value.
• The angle of a chamfer is not taken — with that angle the cut does not meet the other line. Make the angle smaller.
• The legs of a chamfer went the other way round — click the corner nearer to the line the first value should run along.
• The click did not take the corner — not exactly two lines meet at that point, or two of them lie along one straight line (180 degrees). Click right on the vertex of the corner, or on the two lines that meet there at an angle.
• A line was not taken and the status names a point — that is a straight joint: two chosen lines lie along one straight line and the third would have fallen on it. Let go of the line already standing at that point, or choose another pair.
• A click by a crossing took no corner — click nearer the crossing, inside the corner you want.
• The wrong corner of the four at one point was taken — the cursor has to stand in that sector, and where a line was picked first, only the corners that line takes part in are among the answers.
• A click by the end of a fillet took the line rather than a corner — the line goes on from the arc along its tangent there, and there is no corner.