Single Curve Assistant and angle query

Single Curve Assistant — CAPCAD_CURVE_TANGENCY

What it does

It works on one curve at a time. When you pick the curve, the assistant takes it over: every edit deletes the entity in the drawing and draws the new result in its place. There is no separate preview — what you see in the drawing already is the result.

A red round marker follows the current vertex. It is erased when the window closes.

Workflow

1. Run CAPCAD_CURVE_TANGENCY. The window opens with no curve; the fields are empty.
2. Select curve (1). The window hides, the CAD asks Select the curve: and accepts a line, polyline or arc. The footer reports how many vertices the curve has.
3. Walk the vertices with the counter (4) or grab one in the drawing with Get (5). The Segment ahead frame then describes the segment that starts at that vertex.
4. Fix it: type a radius and press Enter, or use − and + (13, 14); or click Make tg (18), Remove arc (19) or To chamfer (20).
5. For the whole curve, tick one of the Utilities and click Apply (30).
6. Reset (2) undoes everything at once, back to the curve as it was when it was selected.

The form

The window as freshly opened, before any curve is picked. The capture is of a Portuguese session; the numbering is the same in both editions, and the table gives the English captions.

The status label, to the right of the Length box (21) and showing — while there is no curve, is the diagnosis of the segment ahead:

When the radius will not go in

The Enter in the radius box (12) only works on an interior vertex — neither the first nor the last. At the ends the message is Radius needs an interior vertex (not first/last).

A radius that is too large is refused as well (Radius … not possible at vertex …): the tangent points would fall outside the neighbouring straights, and no fillet is possible. Reduce the radius, or use + vtx to lengthen the short leg.

Remembered between sessions

Nothing. Every CAPCAD_CURVE_TANGENCY opens the window blank, with radius 10, step 1, Apply radius to all selected and Zoom and Pan unticked. The window is also not single instance: running the command again opens a second window, with its own managed curve.

Angle at a point — CAPCAD_ANGLE_QUERY

What it does

It reports the direction of the tangent of the curve at the point you clicked, and along with it the distance travelled along the curve to get there. It draws nothing, selects nothing and changes nothing.

1. Run CAPCAD_ANGLE_QUERY.
2. Select a curve (click at the point of interest): — click on the stretch whose direction interests you. Lines, polylines and arcs are accepted, as are circles, ellipses, splines and 3D polylines; anything else is refused with Must be a line, polyline or arc., and a curve CapCad cannot read fails with Could not read the curve.
3. The command line answers, for example:

Angle at point: 87.412°  (station 143.905).

The angle is measured from the positive X axis, counter-clockwise, and normalised into the range 0° to 360°. The station is the length along the curve from its start to the foot of the perpendicular of your click — not the straight-line distance.

The click point is projected perpendicularly onto the curve. When that projection does not exist — a click well beyond one of the ends, for instance — the answer is Angle at point not found.

Use it to set the rotation of a block or a text that has to follow the road. To copy the angle straight from one entity to another, without typing, the command is CAPCAD_ROTATION_MATCH of Draw and modify.

Notes

• The assistant's X and Y boxes do not move the vertex. They show the position of the current vertex and are rewritten on every change of index; what you type into them is not used. To move a vertex, use the CAD's grips and then Update (3).
• Each edit is one undo step. The assistant does not group the edits: one Ctrl+Z undoes only the last delete-and-redraw, not the whole working session — and the first Ctrl+Z may well undo the red marker rather than the edit. To go back to the start, use Reset (2), which is what exists for that.
• The entity changes identity on every edit. Since every edit deletes and redraws, the polyline's handle in the drawing is not the one it started with. External references to that handle — data attached by other commands, for example — do not survive an editing session.
• "To chamfer" (20) and "Apply chamfer to all" (24) are different things. Button 20 only zeroes the curvature of an arc that already exists, leaving a chamfer between the tangent points that were already there. Utility 24 creates the chamfer at a sharp corner, from the radius in box 23 — as if filleting, but with a straight line instead of the arc.
• The command is not single instance. Unlike almost every other CapCad window, running it twice opens two windows. Each manages its own curve, and both write into the same drawing.
• The prompts and messages are in English on every profile — Select the curve:, Pick near a vertex:, Angle at point:, Filleted 7/9 corners.
• Three buttons of the taxiway assistant open this same window. Make tangent, Make arcs and Tangency assistant, in the Taxiway assistant, all run CAPCAD_CURVE_TANGENCY — there are not three different behaviours behind them.

See also

• Curve Utilities — the Fillet conditional and the tangency utilities applied to a whole selection instead of one curve.
• Polyline and segment tools — adding, removing and cycling vertices from the command line.
• Draw and modify — CAPCAD_ROTATION_MATCH and CAPCAD_ROTATION_ADD, which use the same tangent angle.
• Offsets — the neighbour on the Geometry split button.