Menu path
CAD > Insert > Arc
Arcs are portions of circles or ellipses that you can insert in your roof designs. They're useful for creating curved gutters, rounded roof edges, and other curved roofing elements.
🧾 What arcs are
An arc is defined by a centre point, start angle, and end angle. It's essentially a portion of a complete circle or ellipse. Circular arcs have equal first and second axes, while elliptical arcs have different axis lengths.
Arcs are technically defined by five associated points: the origin (centre), the start of circumference, the end of circumference, and the first and second axis endpoints. These points can be selected using the snap/help button for exact positioning, but cannot be deleted without deleting the entire arc.
🔧 Arc insertion methods
The Arc Insert command opens the Arc Insert sub-menu with several insertion options:
3-Points Method
Creates an arc passing through three selected points:
Select the first point (start of arc's circumference)
Select the second point (defines size and orientation)
Select the third point (end of arc's circumference)
Note: If the three points are in a straight line, no arc will be inserted.
Radius Method
Creates an arc with radius defined by two points and angle by a third:
Select the origin (centre) of the arc
Select the start point of the arc's circumference
Select a third point to define the subtending angle
The arc extends anti-clockwise from the second to third point location around the origin.
Radius= Method
Creates an arc with a specified radius value:
Enter the radius value
Select the origin point
Select two points to define the subtending angle
Diameter= Method
Creates an arc with a specified diameter value:
Enter the diameter value
Select the origin point
Select two points to define the subtending angle
The arc endpoints lie at half the specified diameter distance from the origin.
Angle= Method
Creates an arc with specified radius and angles:
Field | Description |
Radius | Sets the radius of the arc |
Start Angle | Sets the start angle, measured anti-clockwise from the X-axis |
Sweep Angle | Sets the sweep angle, measured anti-clockwise from the start angle |
🔧 Arc Fillet
The Arc Fillet command creates arcs as fillets between existing elements:
Two point locations
A point location and a line or circle
Two lines, circles, or curves
A line and a circle or curve
Note: Fillet arcs never exceed 180 degrees.
🛠 Working with arcs
Once inserted, arcs can be:
Trimmed and divided
Used to generate points around their circumference
Listed alongside circles in the List Count command
Listed as circles by the List Verify command
💡 Display settings
Arc and circle visibility can be controlled through Defaults > Vis-Model by setting the Circles modifier to No to suppress their display.
⚠️ Important notes
All arc angles are measured anti-clockwise in the current view
The second axis point is always at right angles to the start point relative to the origin
Elliptical arcs can be created by specifying different axis lengths
Arc endpoints lie on projection lines from the origin at the specified radial distance