Struct Arc 

pub struct Arc {
    pub circle: Circle,
    pub start: Vector3,
    pub end: Vector3,
}

A circular arc: the part of circle from start counter-clockwise (seen with circle.normal towards the viewer) to end — all of it when start and end coincide.

Fields

circle: Circle

start: Vector3

end: Vector3

Implementations

impl Arc

pub fn transform(&self, motion: &Motion) -> Self

The arc moved by motion. A mirror turns counter-clockwise into clockwise, so the mirrored arc runs from its end to its start.

pub fn could_be_closed(&self) -> bool

Whether the arc could be the whole circle.

pub fn angle(&self) -> GeopResult<Scalar>

The angle the arc turns through, in radians, in (0, 2 pi]: an enclosure, for what is measured — its length (Arc::length). The whole turn for an arc that could be closed, as Arc::sweep takes it.

pub fn length(&self) -> GeopResult<Scalar>

How long the arc is: its radius times the angle it turns through.

pub fn sweep(&self) -> f64

The angle the arc turns through, in radians, in (0, 2 pi], as a plain f64: only ever used to choose a point along the arc (see Arc::point_at); what is measured takes Arc::angle.

pub fn point_at(&self, fraction: f64) -> GeopResult<Vector3>

The point fraction of the way along the arc, by angle: start at 0, end at 1.

The angle is computed in f64 (see Arc::sweep) and taken as sharp — legitimately: which point is “0.3 of the way” is a choice the caller makes, and any angle within rounding of it serves that choice equally well. What the result has to be honestly is a point on the circle, and it is, since it is built from the circle itself.

pub fn tangent_at(&self, p: &Vector3) -> GeopResult<Vector3>

The unit tangent at p, a point of the arc, pointing the way the arc runs.

pub fn to_curve(&self) -> GeopResult<NurbCurve3D>

The arc as a curve, the way the kernel builds every arc: rational quadratic pieces of at most a quarter turn each, on [0, 1], running from start to end exactly.

Where the pieces meet is a free choice (see Arc::point_at): any point of the circle serves. Each piece from P0 to P2 around the center C, turning through phi, has its middle control point where the tangents at its ends meet, C + (P0 - C + P2 - C) / (1 + cos phi), weighted cos(phi / 2) = sqrt((1 + cos phi) / 2) — both read off the ends, so no angle is taken.

Trait Implementations

impl Clone for Arc

fn clone(&self) -> Arc

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Arc

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.