Arc Commands¶

VektorCAD provides three arc commands accessible from Toolbar > Draw > Arc:

Command	Description
ARC	Create arcs using multiple methods (3-point, center, start-end, etc.)
RARC	Create arc by radius, center, start point, and end point
CARC	Create arc by cutting a curve at a specified radius and arc length

ARC Command¶

Creates an arc using various combinations of points, center, radius, angle, chord length, and direction. Arcs are drawn counter-clockwise by default.

Creation Methods¶

Method	Input sequence	Description
3-Point (default)	Start → Second → End	Arc passing through three points
Center-Start-End	Center → Start → End	Arc from center with start/end angles
Center-Start-Angle	Center → Start → Angle	Arc with specified sweep angle
Center-Start-Chord	Center → Start → ChordLength	Arc defined by chord length
Center-Radius-Start-End	Center → Radius → Start angle → End	Arc by center, radius, and angles
Start-End-Center	Start → End → Center	Arc by endpoints and center
Start-End-Angle	Start → End → Angle	Arc between two points with included angle
Start-End-Direction	Start → End → Direction	Arc tangent to a specified direction
Start-End-Radius	Start → End → Radius	Arc between two points with given radius

Keywords¶

Keywords appear at various prompts depending on the creation path:

Keyword	When available	Description
Center	At start point / second point	Switch to center-first method
CenterMark	At start point	Toggle center mark ON/OFF
End	At second point	Switch to start-end method
Angle	At end/center point	Define arc by angle
ChordLength	At end point	Define arc by chord length
Radius	At start point (center mode) / at center point (end mode)	Define arc by radius
Direction	At center point (end mode)	Define arc by tangent direction
Clockwise	At end point (center mode)	Switch to clockwise direction
CounterClockwise	At end point (center mode)	Switch to counter-clockwise direction

3-Point Arc (Default)¶

Command: ARC
Specify start point [Center/CenterMark]: 0,0
Specify second point [Center/End]: 50,30
Specify end point: 100,0

Center-Start-End¶

Command: ARC
Specify start point [Center/CenterMark]: Center
Specify center point: 50,50
Specify start point [Radius]: 50,0
Specify end point [Angle/ChordLength/Clockwise]: 100,50

Center-Start-Angle¶

Command: ARC
Specify start point [Center/CenterMark]: Center
Specify center point: 50,50
Specify start point [Radius]: 50,0
Specify end point [Angle/ChordLength/Clockwise]: Angle
Pick point for angle: 90

Start-End-Radius¶

Command: ARC
Specify start point [Center/CenterMark]: 0,0
Specify second point [Center/End]: End
Specify end point: 60,0
Specify center point [Angle/Direction/Radius]: Radius
Pick point for radius: 40

Start-End-Direction¶

Command: ARC
Specify start point [Center/CenterMark]: 0,0
Specify second point [Center/End]: End
Specify end point: 60,0
Specify center point [Angle/Direction/Radius]: Direction
Pick point for direction: (click to define tangent direction)

RARC Command (Radius Arc)¶

Creates an arc by specifying radius, center, start point, and end point. Useful when the radius is known beforehand.

Prompts¶

Prompt	Description
Specify radius	Enter the arc radius
Specify center point	Center of the arc
Specify start point	Start point (projected onto circle at given radius)
Specify end point	End point (angle direction from center)

Keywords¶

Keyword	When available	Description
Clockwise	At end point (when CCW is current)	Draw arc clockwise
CounterClockwise	At end point (when CW is current)	Draw arc counter-clockwise

How to Use¶

Command: RARC
Specify radius <5>: 25
Specify center point: 50,50
Specify start point: 75,50
Specify end point [Clockwise]: (click or type angle direction)

The arc is drawn from the start angle to the end angle. A live preview updates as you move the cursor for the end point.

CARC Command (Cut Arc)¶

Creates an arc at a specified radius and center that cuts (intersects) an existing curve. The arc is placed at the intersection point closest to where you pick the curve.

Prompts¶

Prompt	Description
Specify radius	Radius of the arc
Specify center point	Center of the arc
Specify curve to cut	Pick an existing entity to intersect with

Keywords¶

Keyword	When available	Description
ArcLength	At curve selection prompt	Set the arc length (default: 5)

How to Use¶

Command: CARC
Specify radius <5>: 10
Specify center point: 50,50
Specify curve to cut [ArcLength]: (pick a line/arc/circle/ellipse/spline)

Supported Entities for Cutting¶

Line
Circle
Arc
Ellipse
Elliptical Arc
Spline

Changing Arc Length¶

Command: CARC
Specify radius <5>: 10
Specify center point: 50,50
Specify curve to cut [ArcLength]: ArcLength
Specify arc length <5>: 8
Specify curve to cut [ArcLength]: (pick curve)

The arc is centered at the intersection point and spans the specified arc length symmetrically.

Clockwise vs Counter-Clockwise¶

Input	Direction
Default	Counter-clockwise (CCW)
Clockwise keyword	Clockwise (CW)
3-Point method	Determined by point positions

Best Practices¶

Practice	Benefit
Use 3-Point for quick freeform arcs	Simplest method
Use Center-Start-Angle for precise arcs	Exact sweep angle control
Use RARC when radius is known	Direct radius input, no calculation
Use CARC for arcs on existing geometry	Automatically finds intersection
Use Direction for tangent arcs	Smooth transitions from lines
Enable CenterMark for dimensioning	Center points for radial dims

Quick Reference¶

Task	Input
3-Point arc	`ARC` → start → second → end
Arc by center	`ARC` → Center → center → start → end
Arc by radius	`RARC` → radius → center → start → end
Cut arc on curve	`CARC` → radius → center → pick curve
Clockwise arc	Type `Clockwise` keyword
Toggle center mark	Type `CenterMark` keyword