# Class: Sketchup::ArcCurve

Inherits:
Curve
show all

## Overview

An ArcCurve is a Curve that makes up part of a circle. This is the underlying class for circles as well.

You can think of ArcCurves as entities that were created with SketchUp's Arc or Circle drawing tools and Curves as entities that were created with the Freehand drawing tool.

However, keep in mind that all Curves in SketchUp are really edges with some extra data attached to them. When you use the API to draw a Curve or ArcCurve, you are really drawing edges.

ArcCurve is a subclass of Curve, so all of the methods that are available to Curves are also available to ArcCurves.

Examples:

``````# Draw a circle on the ground plane around the origin.
center_point = Geom::Point3d.new(0,0,0)
normal_vector = Geom::Vector3d.new(0,0,1)

entities = Sketchup.active_model.entities
first_edge = edgearray
arccurve = first_edge.curve``````

Version:

• SketchUp 6.0

## Instance Method Summary #collapse

• The center method is used to retrieve the Point3d that is at the center of the circular arc.

• The #end_angle method is used to retrieve the angle of the end of the arc measured from the X axis in radians.

• The normal method retrieves a Vector3d that is perpendicular to the plane of the arc.

• The plane method is used to retrieve the plane of the arc.

• The radius method is used to retrieve the radius of the arc.

• The start_angle method is used to retrieve the angle of the start of the arc, measured from the X axis in radians.

• The xaxis method is used to retrieve the X axis of the coordinate system for the curve.

• The yaxis method is used to retrieve the Y axis of the coordinate system for the curve.

## Instance Method Details

### ↑ #center ⇒ Object

The center method is used to retrieve the Point3d that is at the center of the circular arc.

Examples:

``````centerpoint = Geom::Point3d.new
# Create a circle perpendicular to the normal or Z axis
vector = Geom::Vector3d.new 0,0,1
vector2 = vector.normalize!
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_circle centerpoint, vector2, 10
edge = edgearray
arccurve = edge.curve
point = arccurve.center``````

Returns:

• point - a Point3d at the center of the arc if successful

Version:

• SketchUp 6.0

### ↑ #end_angle ⇒ Float

Note:

A bug in SketchUp 2017 and older will report the end-angle for some circles as more than 360 degrees. In such case, subtract 2 * PI from the end angle value.

The #end_angle method is used to retrieve the angle of the end of the arc measured from the X axis in radians.

Examples:

``````# Create a 1/2 circle, normal to the Z axis
start_a = 0.0
end_a = 180.degrees
model = Sketchup.active_model
entities = model.entities
edges = entities.add_arc(ORIGIN, X_AXIS, Z_AXIS, 5, start_a, end_a)
arc_curve = edges.first.curve
end_angle = arc_curve.end_angle``````

Returns:

• (Float)

Version:

• SketchUp 6.0

### ↑ #normal ⇒ Object

The normal method retrieves a Vector3d that is perpendicular to the plane of the arc.

Examples:

``````centerpoint = Geom::Point3d.new
# Create a circle perpendicular to the normal or Z axis
vector = Geom::Vector3d.new 0,0,1
vector2 = vector.normalize!
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_circle centerpoint, vector2, 10
edge = edgearray
arccurve = edge.curve
v = arccurve.normal``````

Returns:

• vector - a Vector3d object if successful

Version:

• SketchUp 6.0

### ↑ #plane ⇒ Object

The plane method is used to retrieve the plane of the arc.

Refer to the Geom module for instructions to create a plane.

Examples:

``````centerpoint = Geom::Point3d.new
# Create a circle perpendicular to the normal or Z axis
vector = Geom::Vector3d.new 0,0,1
vector2 = vector.normalize!
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_circle centerpoint, vector2, 10
edge = edgearray
arccurve = edge.curve
plane = arccurve.plane``````

Returns:

• plane - the plane of the arc if successful

Version:

• SketchUp 6.0

The radius method is used to retrieve the radius of the arc.

Examples:

``````centerpoint = Geom::Point3d.new
# Create a circle perpendicular to the normal or Z axis
vector = Geom::Vector3d.new 0,0,1
vector2 = vector.normalize!
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_circle centerpoint, vector2, 10
edge = edgearray
arccurve = edge.curve

Returns:

Version:

• SketchUp 6.0

### ↑ #start_angle ⇒ Object

The start_angle method is used to retrieve the angle of the start of the arc, measured from the X axis in radians.

Examples:

``````# Create a 1/4 circle, radius of 5, normal to the Z axis
center = Geom::Point3d.new 0, 0, -1
normal = Geom::Vector3d.new 0,0,1
xaxis = Geom::Vector3d.new 1,0,0
start_a = Math::PI/2
end_a = Math::PI
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_arc center, xaxis, normal, 5, start_a, end_a
edge = edgearray
arccurve = edge.curve
start_angle = arccurve.start_angle``````

Returns:

• angle - the angle of the start of the arc if successful

Version:

• SketchUp 6.0

### ↑ #xaxis ⇒ Object

The xaxis method is used to retrieve the X axis of the coordinate system for the curve. Note that the length of the returned vector is equal to the radius of the underlying curve.

Examples:

``````centerpoint = Geom::Point3d.new
# Create a circle perpendicular to the normal or Z axis
vector = Geom::Vector3d.new 0,0,1
vector2 = vector.normalize!
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_circle centerpoint, vector2, 10
edge = edgearray
arccurve = edge.curve
v = arccurve.xaxis``````

Returns:

• vector - a Vector3d object if successful

Version:

• SketchUp 6.0

### ↑ #yaxis ⇒ Object

The yaxis method is used to retrieve the Y axis of the coordinate system for the curve. Note that the length of the returned vector is equal to the radius of the underlying curve.

Examples:

``````centerpoint = Geom::Point3d.new
# Create a circle perpendicular to the normal or Z axis
vector = Geom::Vector3d.new 0,0,1
vector2 = vector.normalize!
model = Sketchup.active_model
entities = model.entities
edgearray = entities.add_circle centerpoint, vector2, 10
edge = edgearray
arccurve = edge.curve
v = arccurve.yaxis``````

Returns:

• vector - a Vector3d object if successful

Version:

• SketchUp 6.0