Expanding Your Shape Vocabulary

The last chapter covered the six tools you will use every day. The Draw menu holds eleven more, and a few of them — construction lines especially — change the way you lay a drawing out. They are worth meeting on purpose rather than stumbling across later.

Prerequisites

• You can start a tool and read the context bar — see Drawing Basic Shapes.

Polygon — PG

What it draws. A regular polygon: a shape with equal sides, such as a hexagon or an octagon.

How to use it:

1. Type how many sides you want — anything from 3 to 1024 — or press Enter to accept the number shown.
2. Pick the centre.
3. Pick a corner, or type the distance from the centre to a corner.

Why that first option matters. The two ways of sizing a polygon have names worth knowing:

• Inscribed (the default) — the polygon fits inside an imaginary circle, so your point lands on a corner.
• Circumscribed — the polygon fits around the circle, so your point lands on the middle of a flat side.

It is not a detail. A hexagonal bolt head is specified across its flats, which is the circumscribed measurement. Use the wrong one and your hexagon comes out the wrong size.

Slot — SL

What it draws. A slot — a straight-sided hole with half-round ends — as one closed polyline.

The default way: pick the centre of each rounded end, then give the width (type it, click the edge, or press Enter for the width shown).

Which to use. Slots on an engineering drawing are normally dimensioned tip to tip, so Overall length (O) usually matches the numbers you have been given. The default asks for centres, which is a different measurement by one slot width.

Ellipse — E

What it draws. An ellipse — a stretched circle.

Pick the centre, then one end of the first axis, then the second axis (type half its length, or click that far away from the first axis).

An axis is a line across the middle of the ellipse. One is longer, one is shorter — but either may be the one you give first. There is no order to respect.

Isocircle only appears while isometric drafting is on. It draws what a circle looks like on the current isometric face — genuinely tedious to construct by hand, and one line of work here. See Drafting Aids.

Afterwards, dragging an axis-end grip changes that axis's length.

Spline — SP

What it draws. A smooth, flowing curve — for contours, cables, landscaping edges and anything else that is not made of straight lines and perfect arcs.

Click a series of points; Enter finishes, and clicking the first point again closes the curve.

The two ways of drawing one, in plain terms:

• Fit points (the default) — the curve passes through every point you click. Intuitive, and what you want most of the time.
• Control points — your clicks form a frame that pulls the curve towards it without the curve touching them. Less obvious, but it gives smoother, more predictable shapes.

If a spline loops oddly at a sharp turn, turn on centripetal knots (K) and draw it again.

A spline's grips are whichever kind of point it was made with. Dragging a fit point re-fits the curve through its new position.

Construction Line — CL — and Ray — RA

What they draw. Lines with no ends — they run right across the drawing, however far you zoom out.

What they are for. Laying a drawing out. Before drawing anything real, you rough in the grid: wall centrelines, column lines, the angle a roof runs at. Then you draw proper geometry against them. Draughtspeople have done this with pencil lines for a century; these are the CAD version.

The tool keeps making them until you press Enter or Esc.

That last option is the quietly valuable one. Because construction lines land on a layer of their own, you can switch the entire scaffold off with one click when you are finished with it, instead of hunting down lines one at a time. See Working with Layers.

Ray (RA) is the half-version: pick a start point, and each click makes a line that begins there and runs on forever through the click.

When part of the scaffold should become real geometry, Trim and Break cut construction lines and rays down into rays and ordinary lines.

Donut — DON

What it draws. A filled ring, placed at each click or typed point, until Enter or Esc.

A lone number typed at the centre is taken as the outside diameter.

The common use: set the inside diameter to 0 and you get the solid dots that mark connections on services and electrical drawings.

Revision Cloud — RC

What it draws. A bubbly outline — a run of small arcs — around part of the drawing, as one closed polyline.

What it is for. Marking what changed since the last issue of a drawing, so the person reading it can see at a glance what to look at. It is a standard drafting convention, not decoration.

Note that arc size is a paper measurement. It stays the same visual size on the printed sheet whatever scale the drawing is at, so your clouds always look right.

Wipeout — WO

What it draws. A shape that hides whatever is underneath it — a blank area to put a note in, over a busy part of a drawing.

Click each corner; Enter, C, or clicking the first point again closes it.

The rule that explains most surprises: a wipeout hides everything drawn before it, and nothing drawn after. So if something you expected to be covered is still showing — or something you wanted to keep has disappeared — the stacking order is the problem. Fix it with Modify ▸ Draw Order.

Before printing, turn frames off (F), so the mask itself leaves no outline on paper.

Divide — DV — and Measure — ME

Two tools that place points along an object you already drew. They are the quickest way to set things out at a regular spacing.

Divide cuts an object into a number of equal parts. Hover over a line, arc, circle or polyline to see where the points would go, type how many parts you want (2 to 10,000), then click the object. It carries on with the next object until you press Enter.

Measure places a point every so far along the object — you give the spacing, not a count. It starts from whichever end is nearer the cursor.

So: "split this wall into 5" is Divide. "a point every 600 along this wall" is Measure.

If you cannot see the points you just placed, it is the point style: points use one style for the whole drawing, set in Format ▸ Point Style, and the default is deliberately small.

To place blocks along an object instead of points — fence posts, balusters, light fittings — use Blocks ▸ Divide and Measure with Blocks. See Working with Blocks.

Next Steps

Next: Typing Coordinates and Values