Circles and arcs
Circles and arcs appear everywhere — columns, pipes, door swings, curved walls. Learn the drawing methods and when each one is the right choice.
In this lesson you will
- Draw circles by centre, diameter, points and tangents
- Draw arcs with the common methods
- Draw a door swing
- Round corners with FILLET
Circles
| Method | How | Typical use |
|---|---|---|
| Centre, radius | C, pick centre, type radius | Most circles |
| Centre, diameter | C, pick centre, D, type diameter | Pipes and columns sized by diameter |
| 2-point / 3-point | C, 2P or 3P | Circle through known points |
| Tangent, tangent, radius | C, T | A circle touching two objects |
Arcs
ARC (A) has many methods; you need two or three. 3-point is the default: start, a point on the arc, end. Start, Centre, End is common for door swings. Arcs are drawn counter-clockwise by default — if yours bulges the wrong way, pick the points in the opposite order (or hold Ctrl while picking to flip direction).
Drawing a door swing
Door swings are usually made into blocks so you draw them once — see the Blocks lesson.
- 1Draw the door leaf: a line 820 long from the hinge point, perpendicular to the wall.
- 2Start
ARC, chooseC(centre) and pick the hinge point. - 3Pick the end of the door leaf as the start point.
- 4Pick the other side of the opening as the end point.
Rounding corners with FILLET
FILLET (F) joins two lines with an arc of a set radius. Type R to set the radius, then pick the two lines. Radius 0 makes a sharp corner — the fastest way to tidy up two lines that overshoot or fall short. CHAMFER (CHA) does the same with a straight cut.
Quick reference
| Command / tool | How to start it | What it does |
|---|---|---|
| CIRCLE | C | Draws a circle |
| ARC | A | Draws an arc |
| FILLET | F | Rounds or squares a corner |
| CHAMFER | CHA | Bevels a corner |
Common mistakes
Arc goes the wrong way.
Arcs run counter-clockwise; reverse the pick order.
Circles look like polygons.
Display only. Type
REGENor raiseVIEWRES; the geometry is a true circle.
Exercise
Column grid and a curved bay
- Draw four 300-diameter columns at the corners of a 6000 × 6000 square.
- Draw a 5000-radius arc from one corner column to the next to make a curved bay.
- Draw two lines meeting at a rough corner, and fillet them with radius 0.
- Fillet a rectangle's corners with radius 500.
You should end up with: Columns, a curved bay and clean corners.
Checklist
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Lesson quiz
Which circle method draws a circle touching two existing objects?
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